Laboratory Manual for the Evaluation of Non-automatic Weighing Devices
Procedure
Category: Mass
Procedure: Laboratory Manual for the Evaluation of Non Automatic Weighing Devices
Date: 1997-01-01
Part 1 - General Information
1. Purpose of this manual
2. Scope
3. Abbreviations used in this manual
4. Review and up-date of the requirements, communication and confidentiality
5. Weighing devices and major components subject to approval evaluation
6. Request for approval and assistance to be provided during evaluation
7. Selection criteria for sample devices
8. Representativeness of sample devices and peripheral equipment submitted for evaluation
9. Testing, marking and approval of complete devices and separate components
10. Alteration, modification and adjustment during evaluation
11. Repeatability of tests during evaluation
12. Alterations subsequent to approval
13. Updating designs pursuant to changes in specifications
14. Limits of error
14.1 General
14.2 Limits of error applicable to complete devices and major components tested separately
14.3 Limits of error applicable to multiple range and multi-interval devices
15. Determining the error before rounding - digital-display devices
15.1 Enhanced resolution
15.2"Small weights" method
16. Increasing and decreasing load tests - selection of loads
17. Sequence of tests
18. Adjustment and calibration of the device during evaluation
18.1 General
18.2 Adjustment of calibration points
18.3 Temperature of device at time of adjustment
18.4 Warm-up of device before testing
18.5 Preloading (exercising) the device before testing
18.6 AZSM adjustment
19. Devices equipped with izsm
20. Control of the environment
21. Separate testing of electronic indicators - method and equipment
21.1 Tests using a load receiving/weighing element or load cell installed in a dead load tester
21.2 Simulator tests
Part 2 - Evaluation of Metrological Features
1.0 Marking - generalities
2.0 Sealing
3.0 Indication and registration - representation
4.0 Recorded representation (printed)
5.0 Values defined
6.0 Agreement of registrations
7.0 Price computing feature
8.0 Recorded representation of gross, tare and net weights
9.0 Manual weights entries
10.0 Indicating zero and negative values
11.0 Load receiving/weighing element
12.0 Load cell - relationship of VMIN and d
13.0 Damping means and updating rate of weight/price data
14.0 Limits of indication
15.0 Zero setting mechanisms
16.0 Available section
17.0 Tare
18.0 Motion detection
19.0 Tilting (off-level effect)
20.0 Segment verification
21.0 Multiple deck weighing systems
22.0 Multi-interval devices and multiple range devices
23.0 Devices used for direct sale to the public
24.0 Weigh-in/weigh-out systems
25.0 Non metrological functions
Appendix 2-A Abbreviations and symbols accepted in Canada
Appendix 2-B Draft Specifications for Metrological Audit Trails (May 1996)
Part 3 - Performance Tests
Devices to be tested for influence factors and disturbances
Recommended Test Sequence
LG-3.01 Linearity, hysterisis and repeatability at ambiant temperature
LG-3.02 Load discrimination
LG-3.03 Eccentricity
LG-3.04 Tilting (off level position)
LG-3.05 Suitability of the level indicator
LG-3.06 Warm up time
LG-3.07 Power interruption
LG-3.08 Ac voltage variations
LG-3.09 Dc voltage variations
LG-3.10 Immunity to radiated electromagnetic field
LG-3.11 Susceptibility to magnetism - magnetic loads
LG-3.12 Susceptibility to magnetism - ferromagnetic plate
LG-3.13 Temperature effect on linearity, hysteresis, repeatability
LG-3.14 Creep and creep-return-to-zero
LG-3.15 Temperature effect on the no-load indication
LG-3.16 Damp heat, steady state
LG-3.17 Electrostatic discharge test
LG-3.18 Short time power reduction test
LG-3.19 Burst test
LG-3.20 Endurance (permanence) test
Part 1 - General Information
The purpose of this manual is:
- to provide detailed criteria enabling manufacturers of weighing devices, technologists of the Measurement Canada Approval Services Laboratories and metrologists of United States National Type Evaluation Laboratories to determine whether the design, operation and characteristics of the devices they build or evaluate meet the requirements or the intent of the requirements prescribed by the Specifications for Non Automatic Weighing Devices; and
- to describe the laboratory evaluation and test procedures for non automatic weighing devices so as to ensure that they are applied uniformly.
Warning: from time to time the criteria provided in this manual may have to be updated due to weighing device technology changes. It is recommended that manufacturers contact the manager of the Approval Services Laboratories to discuss any new and special features that they plan to incorporate into their devices to ensure that they comply with the requirements.
This manual provides the examination criteria and test procedures for non automatic weighing devices and major components thereof that may be subject to separate evaluation.
A non automatic weighing device is a weighing device that requires the intervention of an operator in the weighing process. Such devices weigh commodities statically and require the intervention of the operator during the weighing process, for example to apply or remove the material to be weighed from the load receiving element, to read the weight or initiate the printing of tickets, etc.
Examples of non automatic weighing devices are
- retail computing scales used in grocery stores to weigh food in the presence of consumers;
- railway track scales used for the static single-draught weighing of railway cars;
- vehicle-mounted scales used to weigh statically anhydrous ammonia (NH3).
An automatic weighing device weighs without the intervention of an operator and follows a predetermined program of automatic processes that are characteristic of the device. Weighings can be done in motion or statically.
Examples of automatic weighing devices are
- continuous totalizing weighing devices (commonly called conveyor belt scales);
- discontinuous totalizing weighing devices (automatic bulk weighers);
- self-indicating railway track scales (commonly called in-motion railway scales);
- checkweighing machines;
- weight grading machines;
- automatic weight fillers.
Note: An automatic weighing device designed for the static weighing of prepackaged commodities of variable weight to which accessories are attached to automate the application and removal of packages remains in the non automatic category although the system is somewhat automated.
3. Abbreviations Used in this Manual
Abbreviations
| AC | Alternating Current | |
| AZSM | Automatic Zero-Setting Mechanism | |
| Max | Maximum Device Capacity | |
| CDN | Canadian | |
| CofZ | Centre of Zero | |
| d | Scale Interval (also: division, graduation) | |
| DC | Direct Current | |
| DUT | Device Under Test | |
| e | Verification Scale Interval | |
| IZSM | Initial Zero-Setting Mechanism | |
| LCD | Liquid Crystal Display | |
| LED | Light Emitting Diode | |
| LRW | Load Receiving/Weighing Element | |
| MC | Measurement Canada | |
| Emin | Minimum Permissible Error | |
| Emax | Maximum Permissible Error | |
| n | Number of Interval (graduations, divisions) | |
| OIML | International Organization of Legal Metrology | |
| POS | Point-of-Sale System | |
| RH | Relative Humidity | |
| SAZSM | Semi Automatic Zero-Setting Mechanism | |
| VDT | Video Display Terminal | |
| ZU | Zone of Uncertainty | |
| +ve | Positive | |
| -ve | Negative | |
| Technologist means a member of the staff of the Measurement Canada Approval Services Laboratory who is responsible for evaluating devices. | ||
| Laboratory means the Approval Services Laboratories | ||
4. Review and Up-Date of the Requirements, Communication and Confidentiality
Evaluation for approval usually consists of three parts: (1) examination of the design of the device; (2) performance testing, including susceptibility to influence factors; and (3) durability testing. Examination of the design is intended to ensure that the device conforms to prescribed standards, is appropriate to the intended use and has the characteristics that will ensure accurate measurement and reasonable protection from fraud. Such examination is particularly important when a device has new or unusual characteristics or features. The technologist has to determine whether these new characteristics meet the requirements. Any major question will be reviewed by Policy and Engineering. This manual will be updated from time to time to take into account of technological changes. Good communications internally and with clients are essential to the effectiveness of the device approval program.
All information relating to the design, performance and intended use of devices submitted for approval is confidential. The Laboratory is bound to protect this information and must limit access to it, or to data developed during the approval process, to properly authorized organizations or individuals (usually the applicant or manufacturer).
The technologist is not necessarily an expert in the design of weighing devices. When a noncompliance comes to light, the technologist is not required to determine the cause or suggest ways of correcting it. The technologist informs the applicant, who is responsible for solving the problem.
5. Weighing Devices and Major Components Subject to Approval Evaluation
Weighing devices and major components are normally examined and tested entirely in the Laboratory. However, some devices and load receiving/weighing elements, because of their size or capacity and the present limitations of the Laboratory, are evaluated and tested partly or entirely in the field. In addition, some peripheral devices that perform simple complementary metrological functions such as price computation or that cannot affect the performance of the device to which they are interfaced are evaluated and tested in the field only. Such is the case of a printer that merely reproduces the weight values displayed by the device. The table below gives an overview of which device types are evaluated in the laboratory and which are evaluated in the field.
| Device Type | Test Location |
Any electronic or mechanical primary indicating element that performs metrological functions. |
Examined and tested entirely in the Laboratory. |
Secondary indicating element, printer, secondary display, price-computing scale, cash register and any other peripheral equipment that may be interfaced to a device but does not alter the device performance or does not perform metrological functions. |
These elements are evaluated in the field by inspectors on initial inspection of the weighing device. Such elements will, however, be examined and tested by the Laboratory if they are built into a device submitted for approval. |
Cash register/software of a point-of-sale system (POS) that performs significant metrological functions that may affect measurement (functions other than the computation of total prices on the basis of the weight data provided by the weighing element or the scale, and the printing of the data on a cash register tape. |
Examined and tested entirely in the Laboratory. Weighing elements intended to be interfaced with cash registers of that category may be approved separately. |
Complete weighing device and load receiving/weighing element whose capacity is not more than 1000 kg or whose dimensions do not exceed 1.6 m x 1.6 m. |
Examined and tested entirely in the Laboratory, including temperature susceptibility tests and durability tests. |
Complete weighing device and load receiving/weighing element whose capacity is more than 1000 kg to no more than 10,000 kg and whose dimensions do not exceed 1.6 x 1.6 m. |
Examined and tested entirely in the Laboratory. Only partial tests are performed in the environment chamber. There is no durability tests performed. |
Complete weighing device and load receiving/weighing element whose capacity is more than 10,000 kg or whose dimensions exceed 1.6 m x 1.6 m. (This category includes vehicle scales, tank scales, large capacity hopper scales and railway track scales.) |
The examination and testing are conducted in the field in accordance with the requirements of the Weights and Measures document entitled "Class Approval". Note that indicating elements for these types of devices are examined and tested in the Laboratory. |
Load cells. |
Procedure to follow. |
Software that performs significant metrological functions. |
Examined and tested entirely in the Laboratory. A policy, requirements and procedures concerning the evaluation of softwares are being drafted. |
6. Request for Approval and Assistance to be Provided During Evaluation
The applicant must complete the appropriate approval request form and send it to the manager of the Approval Services Laboratories. The applicant must also provide two copies of the instruction manual and the operator's manual, photographs of the device, and blueprints or drawings showing the arrangement of the components of the device. The applicant must provide the Laboratory technologist with all pertinent details concerning the construction, operating and sealing characteristics of the device, the various functions that the device can perform, the intended use of the device, and its installation particulars.
At the technologist's request, the applicant must submit one or more sample devices and one or more pieces of peripheral equipment, such as a printer, that will be of assistance in assessing the operation of the device in association with such equipment. In some cases, the applicant will be asked to supply and assemble the material and equipment necessary to conduct the adequate tests (for example: supports for overhead-rail scales). The applicant must provide all assistance necessary to enable the technologist to properly conduct the evaluation of the device.
The applicant must prepare, set the operating parameters of, calibrate and install, as applicable, the sample devices necessary to allow proper assessment.
The purpose of these measures is to make for more efficient assessment of devices.
7. Selection Criteria for Sample Devices
Criteria have been established to determine the number of devices and the particular devices of the same type or family that are required to be submitted to the Laboratory for type evaluations. Deviations from the criteria occur when the criteria do not target those devices within the family that may represent the most difficult technological challenge to achieve compliance with the requirements. The general criteria are as follows:
- The devices with the largest and the smallest capacity in the family.
- The devices with the largest number of graduations.
- The devices with the smallest interval values.
- The devices whose load receiving element has the largest surface area for a given capacity.
- The various types of load cell or load cells made of different materials (options).
- The device or major component with the fullest options.
- The various power supplies available (DC, AC).
Furthermore, when the housing is available in various materials (plastic, stainless steel), each version must be submitted for radio interference testing (RFI). Each version of the housing must be examined for compliance with general requirements, especially sealing requirements. So-called "intrinsicly safe" housings that operate at low voltages must also have to be submitted.
The technologist, in consultation with the manufacturer, will determine how many and what devices of a family or type have to be submitted to the Laboratory for evaluation.
Note: Large capacity devices such as vehicle scales are tested individually in the field after installation in accordance with the Weights and Measures document entitled "Class Approval". Indicating elements of such devices, however, must be of a design approved by the Approval Services Laboratories.
8. Representativeness of Sample Devices and Peripheral Equipment Submitted for Evaluation
The sample device submitted for evaluation and approval testing must be complete in assembly and representative of the model that will be marketed.
If the device can be used with one or more peripheral modules, such as a printer, or if the device can be configured or adjusted remotely by means of a device such as a computer, the applicant must provide a representative peripheral module to allow assessment of the compatibility and operation of the device when connected to peripheral modules.
A device or major component may be designed to perform functions that are not allowed in Canada but are authorized in other countries, for example, use of a unit of measurement prohibited in Canada but allowed in the United States. The device may have such functions provided that the prohibited features can be deactivated and sealed.
A counting feature incorporated in weighing devices is not tested by the Laboratory. It may, however, remain active and be used in trade. Devices used to count numbers of units are not subject to the Weights and Measures Act.
9. Testing, Marking and Approval of Complete Devices and Separate Components
Complete weighing devices consisting of an indicating element and a load receiving/weighing element in the same housing are tested as complete units and are approved as such. The major components of such devices cannot be separated and connected to other components to form a new device. A single identification plate giving all the prescribed information is required.
Complete weighing devices made up of individual components or modules connected together are tested as complete units if the applicant specifies that the modules are not intented to be separated and connected to other modules approved separately to form another device. In this case, a single approval notice will be issued for the complete device. The Notice of Approval will state that the modules of the device cannot be separated and used with other modules to form a different device. A single identification plate for the entire device giving all the prescribed information will be required.
If the applicant indicates that the major components of a device like that described in the foregoing paragraph may be used with other major components approved separately, the latter components will then be tested separately to a limit of error equal to 0.7 times the acceptance limit of error normally applied to a complete device. Each major component of the device will have to bear its own identification plate giving the prescribed information. A single Notice of Approval may be issued for the complete device stating that the major components of the device may be separated and connected to other compatible approved modules, or each major component may be approved separately.
Major components submitted individually for approval are tested separately. In this case, a tolerance of 0.7 times the acceptance limit of error normally applied to a complete device will be used. These components will be approved separately and may be connected to other compatible approved devices. Each major component must be marked with the prescribed information.
10. Alteration, Modification and Adjustment During Evaluation
The applicant will be informed of the progress of the examination and testing during evaluation and will be notified promptly of any points of noncompliance. The applicant may then make the necessary corrections or adjustments. The technologist will ensure that any alterations or adjustments made have corrected the noncompliance. The technologist will also have to ensure that any alterations or adjustments made have not changed other characteristics already verified and tested. Where alterations or adjustments are made to a device during evaluation, the technologist will have to determine from the nature of the alteration or adjustment whether some or all of the tests have to be repeated.
11. Repeatability of Tests During Evaluation
The Laboratory endeavours to design and execute the tests in a way and under conditions that ensure as much reproducibility of the results as possible. Some degree of variation, however, is unavoidable. Devices that clearly do not meet the performance requirements would not meet them even under more controlled conditions, no matter how many times the tests were repeated.
A device whose performance is marginally unsatisfactory may be able to meet the limits of error once out of two or three times if the tests are repeated several times. The performance of such a device is nevertheless unsatisfactory.
The Approval Services Laboratories is under no obligation to repeat any tests or portions of tests at the applicant's request where such tests have been duly performed and any repetition of them would add nothing to the evaluation of the device.
12. Alterations Subsequent to Approval
The manufacturer or the applicant must notify the Approval Services Laboratories of its intents to make alterations to the design of an approved device or major component. The alterations may be major or minor. They can include changing the appearance of the housing, changing the material of which the housing is made, physical reorganization of the electronic cards, modification of the software, additional features or options, and so on.
Depending on the scope of the alterations and their potential impact on the performance of the device and its overall compliance with requirements, theApproval Services Laboratories may merely endorse the file and update the Notice of Approval if necessary, or it may carry out a re-examination and partial or complete retesting of the device.
Where the Approval Services Laboratories deems necessary, it may ask the manufacturer to submit a device for examination.
13. Updating Designs Pursuant to Changes in Specifications
When ministerial design, composition, and construction specifications are changed, the designs of devices approved prior to the change in the specifications do not have to be altered to meet the new requirements. They may continue to be marketed without alteration.
Unless otherwise indicated, changes to performance requirements, such as the limits of error, apply to all designs of device even if they were approved prior to the introduction of the changes.
The limits of error depend upon the class designation of the device and its value of verification scale interval "e" (most of the time e = d (graduation)). Contrary to the previous weights and measures requirements, the limits of error are the same for increasing and decreasing loads, and they are not increased by half-graduation for digital-display devices.
The following graph shows a typical performance curve of a weighing device at one temperature, the acceptance limits of error applicable to a Class III, 50 kg x 10 g device and the previous Canadian limits of error.
| Legend: | |||
| 1 | First tolerance step | 0-500 e | |
| 2 | Second tolerance step | +500-2000 e | |
| 3 | Third tolerance step | +2000-4000 e | |
| 4 | Turning point of old limits of error | ||
| 5 | Previous Canadian percentage limits of error | ||
| 6 | Increasing-load performance curve | ||
| 7 | Decreasing-load performance curve | ||
| 8 | Linearity; increasing-load error | ||
| 9 | Hysteresis error | ||
| 10 | Sum of errors | ||
14.2 Limits of error applicable to complete devices and major components tested separately
The full acceptance limits of error apply to complete devices subjected to approval testing.
When a major component, such as an electronic indicating element or a load receiving/weighing element, is tested separately, the limits of error that apply are 0.7 times the acceptance limits of error normally applied to a complete device. This does not apply to a major component that is the only element likely to produce measurement errors (linearity, hysteresis, repeatability and so on) because of disturbances or influence factors (for example, a load receiving/weighing element that produces a digital signal interpretable by computer software). In this case, the full acceptance limits of error will be granted to the load receiving/weighing element.
14.3 Limits of error applicable to multiple range and multi-interval devices
A multiple range device has two or more weighing ranges with different capacities and different intervals for the same load receiving/weighing element, and each range extends from zero to its maximum capacity. Each range is considered a separate device. The limits of error for each range are determined on the basis of the value of the verification scale interval of that range.
A multi-interval device has a single weighing range divided into partial weighing ranges with different intervals, and the weighing range is determined automatically by the load applied, for increasing and decreasing loads. The limits of error are determined on the basis of the class of the device and the value of the verification scale interval "e" of the partial range corresponding to the load applied.
The following example shows how to determine the limits of error applicable to a Class III 15 kg weighing device with partial ranges and verification scale intervals "e" (graduations) set as follows:
First range: 0-2 kg x 1 gram
Second range: 2-5 kg x 2 grams
Third range: 5-15 kg x 5 grams
The acceptance limits of error applicable to Class III weighing devices are:
| Load expressed in number of verification scale intervals "e" | Acceptance limits of error expressed in number of verification scale intervals "e" |
| 0-500 | ± 0.5 e |
| > 500-2000 | ± 1 e |
| > 2000-4000 | ± 1.5 e |
| > 4000 | ± 2.5 e |
The limits of error applicable to each range are therefore:
|
Number of intervals "e" | Value in kilograms | Limits of error (Acceptance) |
| First Range (e = 1 g) | 0-500 e |
0-500 g |
0.5 g (0.5 e) |
| Second Range (e = 2 g) |
0-500 e |
0-1 kg |
N/A |
| Third Range (e = 5 g) |
0-500 e |
0-2.5 kg |
N/A |
15. Determining the Error Before Rounding - Digital-Display Devices
In some cases during approval testing, the internal error or error before rounding will have to be determined in order to accurately establish the performance curve of the device and whether it meets the prescribed limits of error. When the device is tested to full capacity and the errors noted are well within the prescribed limits, direct reading of the registrations may be satisfactory. If the errors are marginal, it will be necessary to determine the internal error or error before rounding.
Two methods may be used: (1) the enhanced resolution of the device; or (2) the "small weights" method (weights equal to no more than 1/10 of the value of the verification scale interval).
If the device has a resolution-enhancing feature (multiplied by 10 or more), this feature will be used during testing.
The following example illustrates the procedure to determine the internal error on a 50 kg x 10 g device. Small weights of 1 gramme (1/10 "d") will be used.
The "break point" refers to the upper and the lower limit of the zone of uncertainty (ZU) between two scale intervals. It is the point where the scale first starts to enter or leave the ZU. For example, a device displays 10.00 kg; small weights are added in units of 1 gramme, and the device begins to display in alternance 10.00 kg and 10.01 kg. The device has entered the zone of uncertainty. The following graph illustrates the upper and lower limits of the ZU (breakpoints). The lower limit of ZU is at point A, and the upper limit of ZU is at point B. At point C, a stable indication is provided.
To test a scale using error weights, it is necessary to know "where you are" within a scale interval (to have a reference point). The zero reference point is the point within the zero interval at which the scale is located when under zero load. It is necessary to establish the true "zero reference point" location in order to determine the relative location of the ZU within the interval.
Location of the Zero Reference Point The AZSM must be deactivated. Place error weights (10 x 1/10 d) on the scale and set the device to zero. Remove the weights from the scale in 1/10 d steps until upper limit of ZU1 is reached (point B, graph below). Add 1/10 d to return to a stable indication. This is the starting point for determining the width of zero interval. Add weights in multiple of 1/10 d until the lower limit of ZU2 is reached (point A, graph below). The amount of weights added from the starting point is considered the width of zero. The zero reference point should be at the center of interval or mid distance between ZU1 and ZU2. In such a case, ZU is at mid point of the interval (Mid distance between 0 and + 1d).
If the zero reference point is not located at mid distance of the interval (equidistant from ZU1 and ZU2), any deviation must be taken into consideration in the calculation of internal or true errors.
The width of ZU. This can be done at zero following the determination of the with of zero interval or anywhere within the weighing range. In the following example, a load of 10 kg is used. Small weights are added in units of 1 g until the lower limit of the ZU is reached (breakpoint A). The display alternates between 10.00 kg and 10.01 kg. The amount of weights that must be added to reach a stable indication of 100.01 kg is the width of the zone of uncertainty. The zone of uncertainty should not be more than 0.3 d wide. See the following illustration.
Note: On a multiple range device and a multi-interval device the determination of the location and the width of ZU must be done for each range.
Calculation of internal errors. For the following example it is assumed that the zero reference point is at the mid range of the interval (equidistant from ZU1 and ZU2) and that the width of the uncertainty zone is 0.3 d or 3 g. The device is set to zero and a load of 10 kg is placed on the platter. The device displays 10.00 kg. Small weights are then added by 1 g steps until the display begins to alternate between 10.00 kg and 10.01 kg. One gramme is removed to obtain a stable registration of 10.00 kg. The device is at the edge of the interval or lower limit of the ZU (point C). Knowing that the width of ZU is 3 g and that the ZU is located at the mid range of the interval, since only 2 g are added to reach the breakpoint, the scale has an error of + 1 g. See the following illustration.
E = 3 g - 2 g = 1 g
16. Increasing and Decreasing Load Tests - Selection of Loads
The increasing and decreasing load tests are procedures required to determine the performance characteristics of weighing devices or major components tested separately. These tests are performed several times during the evaluation at room temperature and at prescribed extremes of temperature (generally -10°C, 20°C and 40°C).
At least five known increasing and decreasing test loads (preferably 10 loads), ranging between zero and the maximum capacity, will be applied. The internal error before rounding will be determined for each load unless the error is well within the limits of error.
Known test loads will be selected whose value corresponds as much as possible to the turning points of the limits of error (see items 1, 2 and 3 of the graph in point 14.1 above). These are the critical points where the device is most likely to fail.
The tests described in this manual and the order in which they are to be carried out must be followed as closely as possible. The sequence of tests has been established to simplify the procedure as a whole and to minimize the time required to complete full evaluation of devices. The order in which the tests are to be carried out is given in Part 3 of the present manual.
18. Adjustment and Calibration of the Device During Evaluation
The device will be calibrated as close to zero error as possible before the test program begins, and thereafter, if necessary, only as indicated in the recommended test sequence in Part 3 of the manual. Unless otherwise indicated by the applicant or the manufacturer, the device will be calibrated as close to zero error as possible at 70% of its maximum capacity.
18.2 Adjustment of calibration points
A.Electronic indicating elements evaluated separately
Calibration points normally serve to correct linearity errors of load receiving/weighing elements to which indicating elements are connected. The calibration points of indicating elements tested separately will be set at zero or inhibited. The indicating element will be adjusted to the maximum number of verification scale intervals "e" (counts) requested by the applicant, within the limits imposed by the class of the device.
B. Complete device
The linearity of complete weighing devices will be set as close to zero error as possible at the appropriate time by means of the calibration points.
C. Weighing elements tested separately
The calibration points of a high precision indicating element used as standard for the evaluation of a weighing element will be set to zero effect or inhibited.
18.3 Temperature of device at time of adjustment
All adjustments before and during evaluation will be made with the device at room temperature (.20°C).
18.4 Warm-up of device before testing
The performance of some devices is sometimes affected when the internal temperature (electronic components) varies and is not stable. When a device is unplugged for a length of time and then plugged in again, the manufacturer usually recommends allowing the device to warm up before being used. The device should have a mechanism to prevent the display and printing of weights until the internal temperature is sufficiently stable to allow accurate measurement. The technologist will conduct the test as soon as the device displays a weight value.
18.5 Preloading (exercising) the device before testing
After the device has been assembled and installed, and whenever it is moved and reinstalled, it may be loaded, if necessary, up to its full capacity to "exercise" the load cell or cells before testing. The recommended test sequence and the test procedures described in Part 3 of this manual provide information as to when it is necessary and permitted to "exercise" the device.
Unless otherwise indicated in the description of the test procedures, if the device is equipped with AZSM, the AZSM will be set at the minimum value. If the minimum value is zero, the AZSM will be set at zero. Where a particular procedure specifies that the AZSM is to be deactivated and the device does not allow this to be done easily, the effect of the mechanism will be cancelled by applying a small load (10 d) to conduct the tests.
19. Devices Equipped With IZSM
Some devices are equipped with IZSM. This feature allows rough setting of the zero according to the weight of the platter, platform or load receiving element. This setting operation occurs automatically whenever the device is turned on or plugged in. The IZSM range is usually limited to 20% of the device capacity, but may range up to 100%. The load cells of such devices are likely to operate over a much wider range than the capacity marked on the device. The technologist must therefore perform appropriate tests to ensure that the performance of the device is acceptable over its whole extended capacity.
When the IZSM limit is 20%, the largest load to which the device will be subjected will be 120% of the capacity (capacity + 20%). In this case, all the tests will be carried out while the IZSM is at the maximum (20%). See the following illustration.
When the IZSM limit is 100%, the largest load to which the device will be exposed will be 200% of the marked capacity (capacity + 100%). When the IZSM capacity exceeds 20%, the increasing and decreasing load tests (linearity, hysteresis and repeatability) at room temperature will be performed twice, that is, when the IZSM is at minimum capacity (0%) and maximum capacity (100%). All other tests, including the tests for susceptibility to temperature variations (-10° C and 40° C) will be performed while the IZSM is at maximum capacity (100%). See the following illustration.
The possible adjustment of the IZSM of a separately approved indicating element must not exceed 20% of the maximum approved capacity of the indicating element, because the performance of the load receiving/weighing elements to which it will be associated is not known.
20. Control of the Environment
The environment in which the tests will be carried out is considered constant and suitable when:
- temperature variations during testing do not exceed 2.5° C (total range);
- the relative humidity is sufficiently constant that no condensation is observed on the device or the standard weights during testing; and
- the relative humidity does not exceed 50 %.
During temperature variation susceptibility testing, the rate of passage from one temperature to another must not exceed 1° C per minute.
For a given influence test, one factor is varied at a time (temperature, humidity) while the others are kept constant.
21. Separate Testing of Electronic Indicators - Method and Equipment
Electronic indicating elements may be tested in one of the following ways:
- connected to a suitable load receiving/weighing element;
- connected to a load-cell simulator;
- connected to a load cell placed in a calibrated dead load tester.
The preferred method is that involving the use of a load receiving/weighing element, because, unlike the load-simulator method, it can be used to carry out the whole test program.
21.1 Tests using a load receiving/weighing element or load cell installed in a dead load tester
The accuracy of the load receiving/weighing element or the load cell as regards linearity, repeatability and hysteresis must allow proper evaluation of the indicating element. The intrinsic errors of the load receiving/weighing element or the load cell must not lead to rejection of the indicating elements under assessment.
The performance of the load receiving/weighing element or the load cell must first be checked using a suitably calibrated high-precision reference indicator. The maximum combined linearity, repeatability and hysteresis error must not exceed 70% of the limits of error allowed for a complete device (Except a weighing element that is the only element likely to produce measurement errors; for instance a weighing element that produces digital signals interpretable by a computer software would be given full limits of error). During testing, the load receiving/weighing element or the load cell will be kept at constant temperature and humidity.
The accuracy of the simulator must first be checked to ensure that the intrinsic errors are minimal and will not cause rejection of the indicating element, and that its overall performance makes it possible to properly determine the performance of the indicating element. The linearity and hysteresis of the simulator must therefore be checked first by means of a calibrated high-precision electronic indicator. During testing of the indicating element, the simulator will be kept at constant temperature and humidity.
The precision simulator used depends on the type of excitation current for which the indicating element is set.
Part 2 - Evaluation of Metrological Features
Reference: Sections 49 to 54 of the Specifications
Complete weighing devices and major components (indicating elements and load receiving/weighing elements) of devices tested separately must be marked with certain information in the manner required by the Specifications Relating to Non Automatic Weighing Devices. Complete devices in the same housing or made of non detachable major components are only required to bear one series of markings. Major components of complete devices must be marked individually if they can be separated and interfaced (mixed/matched) to other major components to form a device. Major components submitted for approval evaluation individually are tested separately and are also required to be marked individually.
Remote (secondary) weight displays, slave modules such as printers, keyboards, cash registers and other similar modules that are used in conjunction with approved devices are not required to be marked if they perform no significant metrological functions.
1.1 Marking - Complete Devices
This section applies to complete devices in the same housing or complete devices made of major detachable components interfaced together and not intended to be separated and used in conjunction with other individually approved major components to form different devices. For such devices, only one series of information is required.
The device must be marked with:
1.1.1 the name or trademark of the manufacturer or applicant.
1.1.2 a model designation that positively identifies the device type or design.
1.1.3 a distinctive serial number. The serial number must be prefaced by words, an abbreviation or a symbol that clearly identifies the number as the serial number.
1.1.4 its Canadian Weights and Measures approval number. The approval number must be prefaced with words or an abbreviation that positively identifies the number as the Canadian approval number.
| Acceptable solutions | or | MC AM-4145 | |
| Canadian Approval AM-4145 | or | CND AM-4145 | |
| or | AM-4145 | ||
1.1.5 the accuracy class. The roman numerals I, II, III, III HD or IIII are the markings required to indicate the accuracy class. The roman numeral within an ellipse or a figure approximating an ellipse is the proper way to indicate the accuracy class. The word "Class" followed by the roman numeral is also acceptable.
1.1.6 the maximum capacity (Max) that the device can weigh.
1.1.7 the value of the actual scale interval "d".
1.1.8 the value of the verification scale interval "e", if different from "d". On Class III, III HD and IIII devices, multi-interval and multiple range devices, "e" must equal "d".
Note:
1. Max, "d" and "e", if different from "d", must be marked adjacent to the weight display.
2. If a device has a separate display for customers, Max, "d" and "e", if different from "d", must be marked adjacent to both the operator and the customer weight displays.
3. Max, "d" and "e", if different from "d", must be marked for all weight units that can be displayed (i.e., pounds and kilograms).
| Examples | 10 kg x 5 g | Max 10 kg/20 lb | 10 kg (20 lb) x 5 g (0.01 lb) |
| 20 lb x 0.01 lb | d = 5 g/0.01 lb |
4. The markings of Max, "d" and "e", if different from "d", adjacent to the weight display must reflect actual device operation. For instance, a device that is capable of being configured for either single or multiple range operation must be marked to reflect the configuration selected.
1.1.9 the operating temperature range if different than -10°C to 40°C. For Class I devices, the temperature range must be at least 5°C for Class II devices, at least 15°C and for Class III, III HD and IIII devices, at least 30°C.
| Note: Multiple range and multi-interval devices must be marked with the weight ranges and the corresponding scale intervals. Devices with more than one class designation must be marked with each class designation in clear association with Max, "d", "e" (if different from "d") and the temperature range, if they are different for each class. | ||||
| Acceptable solutions | ||||
| 1. |
Multi-interval device 0-3 kg (0-6 lb) x 1 g (0.002 lb) 3-6 kg (6-15 lb) x 2 g (0.005 lb) |
or |
Max 3/6 kg (6/15 lb) d = 1/2 g (0.002/0.005 lb) |
|
| 2. | Device with more than one weighing range | |||
|
W1 Max 3 kg (6 lb) d = 1 g (0.002 lb) |
W2 6 kg (15 lb) 2 g (0.005 lb) |
|||
| 3. | Device with weighing ranges in different accuracy classes and restricted temperature ranges | |||
|
W1 II Max 3 kg d = 0.01 g e = 0.1 g 10°C/30°C |
W2 III 15 kg 10 g e = d 0°C/35°C |
|||
1.1.10 the verification marks. The device must have an area, either on the marking plate itself or on the device adjacent to the marking plate, suitable for the application of the verification marks. The surface of this area must be at least 1.5 x 2.5 cm (1/2" x 1").
1.2 Marking - Indicating Elements
This section applies to indicating elements that are evaluated and tested separately. Such indicating elements are either submitted to approval evaluation separately or are major detachable components of a complete device and are intended to be used in conjunction with approved and compatible weighing elements to form different devices.
The indicating element must be marked with:
1.2.1 the name or trademark of the manufacturer or applicant.
1.2.2 a model designation that positively identifies the device type or design.
1.2.3 a distinctive serial number. The serial number must be prefaced by words, an abbreviation or a symbol that clearly identifies the number as the serial number.
1.2.4 its Canadian Weights and Measures approval number. The approval number must be prefaced with words or an abbreviation that positively identifies the number as the Canadian approval number. See acceptable solutions in section 1.1.4.
1.2.5 the accuracy class. The roman numerals I, II, III, III HD or IIII are the markings required to indicate the accuracy class. The roman numeral within an ellipse or a figure approximating an ellipse is the proper way to indicate the accuracy class. The word "Class" followed by the roman numeral is also acceptable.
1.2.6 the maximum number of scale intervals (nmax). If the indicating element is approved for two accuracy classes and has a different maximum number of scale intervals for each accuracy class, both maxima must be marked in clear association to the accuracy class designation.
| Acceptable solutions | ||
|
Class III / III HD nmax 3000 / 8000 |
III III HD nmax 3000 8000 |
III nmax 3000 III HD nmax 8000 |
1.2.7 the maximum capacity "Max", the value of the actual scale interval "d" and the value of the verification scale interval "e", if different from "d", must be marked on the indicator adjacent to the weight display when it is interfaced with a weighing element to form a device. This marking reflects the limitation of the complete weighing device. The technologist (ASL) will, however, ensure that indicators have provisions for the marking of this information. See the notes and examples below sections 1.1.8 and 1.1.9.
Note: for multiple range devices, multi-interval devices and indicators with more than one accuracy class designation, see the note below section 1.1.9.
1.2.8 the operating temperature range, if different than -10°C to 40°C. For Class I indicators, the temperature range must be at least 5°C for Class II indicators, at least 15°C and for Class III, III HD and IIII indicators, at least 30°C.
1.2.9 the verification marks. The indicator must have an area, either on the marking plate itself or on the indicator adjacent to the marking plate, suitable for the application of the verification marks. The surface of this area must be at least 1.5 x 2.5 cm (1/2" x 1").
1.3 Marking - Software
1.3.1 For software that is evaluated separate from hardware, the identifying information (manufacturer name, model number and approval number) must be visible on the video display terminal or printable when called up from the menu, or be continually displayed.
For further information regarding the approval evaluation of software, the regarding the approval evaluation of software, the DRAFT Metrological Software Specifications should be consulted.
1.4 Marking - Load Receiving/Weighing Elements
This section applies to weighing elements that are evaluated and tested separately. Such weighing elements are either submitted to approval evaluation separately or are major detachable components of a complete device and are intended to be used in conjunction with approved and compatible indicating elements to form different devices.
The weighing element must be marked with:
1.4.1 the name or trademark of the manufacturer or applicant.
1.4.2 a model designation that positively identifies the device type or design.
1.4.3 a distinctive serial number. The serial number must be prefaced by words, an abbreviation or a symbol that clearly identifies the number as the serial number.
1.4.4 its Canadian Weights and Measures approval number. The approval number must be prefaced with words or an abbreviation that positively identifies the number as the Canadian approval number. See acceptable solutions in section 1.1.4.
1.4.5 the accuracy class. The roman numerals I, II, III, III HD or IIII are the markings required to indicate the accuracy class. The roman numeral within an ellipse or a figure approximating an ellipse is the proper way to indicate the accuracy class. The word "Class" followed by the roman numeral is also acceptable.
1.4.6 the maximum capacity (Max) that the weighing element can weigh.
1.4.7 the value of the minimum verification scale interval (emin) for which the weighing element complies with the requirements and can be set.
1.4.8 the maximum number of scale intervals (nmax) for which the weighing element complies with the requirements and can be set.
1.4.9 the operating temperature range, if different than -10°C to 40°C. For Class I weighing elements, the temperature range must be at least 5°C for Class II weighing elements, at least 15°C and for Class III, III HD and IIII weighing elements, at least 30°C.
1.5 Marking - Load Cells
The marking of load cells is not required until Measurement Canada institutes a load cell testing and approval program.
1.6. Marking - Readability, Location and Permanence
1.6.1 The required information must be complete, legible, accessible and durable. If necessary for clarity, there must be defining words or authorized symbols associated with the numbers (i.e., model numbers, temperature range, etc.). See the list of acceptable defining words and symbols in Appendix 2-A . It is recommended that the height of capital letters be at least 2 mm (OIML R 76-1).
1.6.2 The required information must be appropriately located. Markings may be on either a marking plate affixed to a permanent part of the device, on the device itself, or both. Information that identifies the device (manufacturer name or trademark, model, serial and approval numbers) should be grouped together. Max, "d" and "e" (if different from "d") must be marked adjacent to the weight display(s). See the note below sections 1.1.8 and 1.1.9 for additional information.
1.6.3 The marking must be visible without having to remove a permanent part of the device or having to move or lift the device. Markings must be available with minimum effort and be accessible without disassembly requiring the use of special tools or equipment.
Acceptable locations
- Markings (and/or the marking plate) may be located on the top, sides or front of the device. Markings may be located beneath the platter and fastened to the scale structure if the platter is easily removable (small devices such as computing scales and bench scales).
- Weighing elements. The required information must be on a surface that is an integral part of the chassis. If the information is on a label or a plate, it must be permanently attached to the device. A plate may be rivetted or welded but not affixed with bolts or screws.
- Weighing elements of large scales. Identification information for the weighing elements of vehicle, axle load, floor, livestock, railroad track and large hopper or tank scales must be located near the point where the signal leaves the weighing element (this would be the transverse lever on a mechanical scale and on, or near, the junction box on an above ground scale). In the case of built-in weighing elements (flush mounted), the required information can be placed on the scale chassis and be accessible by the removal of a cover plate.
Non acceptable locations
1. - Under the scale
- Inside a cabinet
- On the back of the device or indicating element if it is difficult to move and it is likely to be located near a wall
- Marking plate affixed to the platter
1.6.4 If Max, "d" and "e", if different from "d", are displayed electronically, such as on a video display terminal, then they must be adjacent to the weight display and continuously displayed when the system is in the weighing mode.
1.6.5 The lettering must be permanent. This requirement also applies to words and symbols for measurement units adjacent to the weight display and to words and symbols that identify or indicate the status of metrologically significant annunciators. Perform the test described in LG-1.01 and grade the permanence of marking.
1.6.6 Plates or other materials (decals, labels or badges) on which the required information is marked must be made of durable material and permanently affixed to the device so that they cannot be easily removed and affixed to another device. Perform the test described in LG-1.02.
1.7 Marking - Special Applications
Certain device types are designed for specific applications. Such devices may incorporate features, perform certain functions or operate in a particular fashion that would not be acceptable for all applications. Since these devices may not meet all the usual requirements, their use is restricted to the specific applications for which they were designed. The device restriction must therefore be permanently and clearly marked adjacent to both the operator and customer weight displays.
Some examples:
Weight Classifiers Digital weight classifiers round weight values up to the next scale interval. They are designed to classify packages within price ranges for shipping, courier or postal applications. Weight classifiers would therefore not be appropriate for use in grocery store applications. Their use is restricted and they must be marked with the following: << Weight Classification Only >> or << Weight Classifier >> or << Postal Scale >>.
Industrial devices Certain devices are designed for industrial applications. They do not incorporate features that are normally required for devices used in direct sales to consumers. For instance, they may not have a display for consumers; the tare feature may not comply with the requirements for devices used in direct sale applications, etc.. These devices, if they resemble devices intended to be used in direct sale applications, must be marked as follows to indicate that they are designed for industrial use only: <<Not for use in Direct Sale to the Public>> or similar language.
1.7.1 The device is marked with the appropriate restriction.
1.8 Marking - Operational Controls, Indications and Features
The marking of operational controls such as keys, push buttons and switches that are strictly for operator use is not required by Measurement Canada. Keys that are visible only to the scale operator need only be marked to the extent that a trained operator can understand the function of each key. It is however recommended that internationally recognized words and symbols be used.
Annunciators that are "metrologically" significant must be marked with words or acceptable symbols. The following are some examples of "metrologically" significant annunciators: centre of zero, "net", "gross" and "tare" weight indications, identification of the weighing element in use on a multi-deck weighing system, the range selected on a manual multiple range device, etc..
1.8.1 Annunciators for metrologically significant features are clearly and permanently marked.
LG-1.01 Permanence of the lettering
Purpose:
This test is aimed at evaluating the permanence of the information to be marked on the device, or a major detachable element evaluated separately, in order to determine if it will withstand wear and cleaning. Markings are subjected to the following tests to simulate accelerated wear. The markings are then compared to a typical set of markings exhibiting various degrees of wear, graded from excessive unacceptable wear (1) to minimal effect (7).
Application
This test is to be applied to all mandatory markings including the manufacturer's name, the model and serial numbers, Max and "d", the unit of measurement associated with weight indications (kg, lb), to other words or symbols associated with metrologically significant annunciators, etc..
Test Procedure:
Attempts are made to remove the marked information, whether on a badge (plate) or on the device itself, using the following means:
| A. | Rub over one letter of the marking twenty (20) times using an ink eraser in the same manner and with the same force as one would normally exert while erasing an inscription written with a ballpoint pen. | |
| Note: | For consistency of application, the laboratories use Eberhard Faber ink eraser type # 101. | |
| B. | Clean (rub 20 times) with the following cleansers which are presumed to be readily available: | |
| 1. | Cleansing liquid and a damp cloth | |
| 2. | "Soft" household cleansing powder and a damp cloth | |
| 3. | Window cleansing fluids and a damp cloth | |
| Note: | For consistency of application, the laboratories use "409" Bon Ami and Windex brands of products for the tests in parts B.1, B.2 and B.3. | |
Interpretation of Results:
The information marked on the label is deemed to be permanent if, after the test, the label receives a grading of four (4) or better.
Samples
Various Degrees of Wear
LG-1.02 Plate, decal - Permanence of installation and durability of the material
Purpose:
To determine whether the label bearing identification markings (manufacturer's name, model and serial numbers, approval number, initial inspection marks or label) is permanently affixed to the device.
Test Sequence:
An attempt is made to remove the specimen label(s) from the device by pulling it off or by prying off a metal badge that is only attached using adhesive. Any means of removal are allowed while a deliberate effort to conceal the removal is made. Such an attempt shall be made at either -10°C and 40°C or at the minimum and maximum operating temperatures specified by the manufacturer.
Interpretation of Results
An identification label is deemed to be permanently affixed to the device if it cannot be removed from the device and installed on another device without exhibiting readily observable signs of tampering. Acceptable indications of tampering are the destruction of the badge by tearing, permanent or extensive wrinkling, or the repeated exposure of the word "Void" upon removal of the badge.
Notes:
1. A plate that is rivetted to the device is deemed to be permanently fastened if the part of the device to which it is attached is not removable
2. For information such as lb/kg, motion annunciator, centre of zero annunciator, tare/net annunciator, Max, "d" and "e" (if different from "d") adjacent to the weight display, etc. (other than the identification markings: manufacturer's name, model, serial and approval numbers), a sticker that is sturdy and will not detach when subjected to the normal conditions of use of the device (heat, cold, humidity, cleaning) is acceptable. It does not have to be of the self-destructive type.
Reference: Section 48 of the Specifications.
Electronic weighing devices must have provisions to the effect that a security seal must be broken, or an audit trail provided, before any adjustment affecting the performance of the device can be made. Only the metrological parameters: that can affect the measurement features, that have a significant potential for fraud, whose range extends beyond that appropriate for device compliance with the requirements or the suitability of the equipment, shall be sealed.
2.1 Philosophy for Sealing
The judgement as to whether or not a method of access represents a "significant potential for fraud" and thus requires sealing, will be based upon the following philosophies.
2.1.1 The need to seal specific features depends upon:
a. The ease with which the feature or the selection of the feature can be used to facilitate fraud; and
b. The likelihood that the use of the feature will result in fraud not being detected.
2.1.2 Features or functions that are routinely used by the operator as part of device operation, such as the setting and maintaining of unit prices in price look-up codes, are not sealable parameters.
2.1.3 If the selection of a parameter (or a set of parameters) would result in performance that would obviously be in error, such as the selection of parameters for different countries, then it is not necessary to seal the selection of these features.
2.1.4 If individual device characteristics are selectable from a "menu" or a series of programming steps, then access to the "programming mode" must be sealable.
2.1.5 If a device must undergo a physical act, such as the cutting of a wire and physically repairing the cut to reactivate the parameter, it would be considered an acceptable way to select parameters without requiring a physical seal or an audit trail.
2.2 Sealable Parameters on Non Automatic Weighing Devices
The following examples of adjustments, parameters and features to be sealed are to be considered "typical" or "normal". The list is not intended to be all inclusive and any other parameters that may affect the metrological functions of a device must be sealed.
If listed parameters or other parameters which may affect the metrological function of a device are not to be sealed, the manufacturer must demonstrate that the parameter will not affect the metrological performance of the device.
| Scale Features and Parameters | |
| Typical Sealable Parameters | Typical Features or Parameters that are Not Required to be Sealed |
|
|
2.3 Other Mechanisms Requiring Sealing
2.3.1 Junction boxes that have adjustment parameters (potentiometers, rheostats, resistors, etc.) must have provisions for applying security seals.
2.3.2 In the case of a complete scale consisting of an electronic indicator and a load receiving element incorporating a junction box or load cells that have built-in calibration/configuration capabilities, and for which the parameters can be changed "remotely" through the indicator keyboard, there must be provisions to seal load cell cables to the indicator and junction box.
2.3.3 If the device is equipped with an automatic or semi-automatic calibration mechanism, the mechanism must be inside the device and there must be provisions to apply security seals so that neither the mechanism nor the calibration process can be altered.
Automatic and Semi-Automatic Calibration Mechanism
An automatic or semi-automatic calibration mechanism is allowed provided the calibration mechanism is internal to the device and neither the mechanism nor the process can be manipulated in a fraudulent manner. Using the calibration mechanism, attempt to calibrate the device: when the device is off level; when there is a load on the platter; and when the weight indication is in motion. Also attempt to put a small load on the platter while the internal mechanism performs a calibration. No erroneous calibration may result from such manipulation.
2.4 Physical Seals
Physical seals comprise "lead" and wire seals, pressure sensitive seals, etc. They may be used to seal certain device categories, features and mechanisms (see sections 2.3 and 2.5).
2.4.1 Means of sealing must be located such that a seal can be applied without disassembly that exposes electronics. Any disassembly must be simple and not require excessive effort or the use of special tools. Devices must be sealable in a manner that prevents disassembly of the device by removing a panel or cabinet to gain access to the adjustments. Removing a protective cover plate to access a junction box is acceptable. Seals must be readily observable.
2.4.2 On small devices (portable) the means of sealing may be under the platter, if the platter can be lifted easily, under the scale or at the back of the scale if the scale is designed so that it can be turned upside down without damage to remove or apply security seals. When a "lead" and wire seal is located under the platform, there must be ample clearance to eliminate the possibility of interference between the seal and the platform.
2.4.3 When two bolts are used for a "lead" and wire seal, the distance between the bolts must be such that the seal will be broken if an attempt is made to unscrew the bolts. The use of a "free-standing bolt" (a bolt that simply passes through a panel and is held in place by a nut on the opposite side of the panel) is not acceptable. Such a bolt may be loosened to the extent that it will rotate in its position, thereby permitting the other bolt to be turned and the wire of the seal manoeuvred over the top of the bolt while turning the "free-standing" bolt to keep the wire from twisting.
2.4.4 Pressure sensitive seals are acceptable under certain conditions. If they cover a hole (e.g., through which a "calibration enable" switch would be activated) the hole must be covered with a suitable plug. The seal must not bridge so as to leave cavities or air pockets under the seal. Cavities and air pockets are weak points that could cause the seal to be easily damaged (see the illustration below).
- Pressure sensitive (paper) seal
- Keylock
- Air pocket (void space)
- Casing
2.4.5 A pressure sensitive security seal is not suitable in an adverse environment (rain, cold, washdown, etc.).
2.5 Sealing Electronic Devices
Electronic devices may be "sealed" by means of an audit trail. The audit trail must comply with the minimum requirements contained in the Draft Specifications for Metrological Audit Trails. Terms used in the following checklist are defined in the Draft Specifications for Metrological Audit Trails which can be found in Appendix 2-B.
First, based upon its configuration and adjustment characteristics, determine to which category the device belongs.
Category 1 A device that does not have remote configuration capability. Usually a device of this category has internal, physical means of adjustment such as dip switches, or configuration and adjustments can only be made through the device keypad when it is in a "calibration" mode.
Category 2:A device offering remote configuration capability for its sealable parameters but providing sealable enabling/disabling hardware to control remote configuration use. Usually, a device of this category can be adjusted through the device keypad, remotely through the ports using an external apparatus such as a computer or using an external device such as an infrared handheld transmitter.
Category 3: A device that provides unrestricted access to its sealable parameters. These are complex devices that are often part of sophisticated measuring systems.
Examination of Category 1 Devices
2.5.1 Access to sealable parameters is protected by:
- a physical seal; or
- an audit trail with two event counters (one for calibration, the second for configuration).
2.5.2 Event counters are non-resettable and have a capacity of at least 000 to 999.
2.5.3 Event counters increment appropriately.
2.5.4 Audit trail information must be capable of being retained in memory for at least 30 days while the device is without power.
2.5.5 Audit trail information must be readily accessible and easily readable.
2.5.6 Accessing the audit trail information for review shall be separate from the calibration mode.
2.5.7 Accessing the audit trail information must not affect normal operation of the device.
2.5.8 Accessing the audit trail information shall not require removal of any additional parts other than normal requirements to inspect the integrity of a physical security seal. (e.g., a key to open a locked panel may be required).
Examination of Category 2 Devices
2.5.9 The physical hardware enabling access for remote communication is located at the device.
2.5.10 Access to sealable parameters is protected by:
a) physically sealable hardware, located at the device, enabling access for remote configuration;
or
b) two event counters (one for calibration, the second for configuration)
2.5.11 The device must clearly indicate when it is in the configuration mode.
2.5.12 Event counters are non-resettable and have a capacity of at least 000 to 999.
2.5.13 Event counters increment appropriately.
2.5.14 If capable of printing in the calibration mode, it must print a message that it is in the calibration mode.
2.5.15 Audit trail information must be capable of being retained in memory for at least 30 days while the device is without power.
2.5.16 Audit trail information must be readily accessible and easily readable.
Examination of Category 3 Devices
2.5.17 The device is equipped with an event logger.
2.5.18 The event logger automatically retains the identification of the parameter changed, the date and time of the change, and the new value of the parameter.
2.5.19 The event counter is non-resettable and has a capacity of at least 000 to 999.
2.5.20 The system is designed to be attached to a printer which can print the content of the audit trail.
2.5.21 The audit trail information must be capable of being retained in memory for at least 30 days while the device is out of power.
2.5.22 The event logger must have the capacity to retain records equal to ten times the number of sealable parameters in the device, but not more than 1000 records are required.
2.5.23 The event logger drops the oldest event when the memory capacity is full and a new entry is saved.
2.6 Notices of Approval
Provisions for sealing some devices or features may be complex and extensive. Certain devices may incorporate audit trails and, in addition, some of their features or mechanisms may be secured using two or more physical seals. Audit trails are also configured differently for different devices.
In order to ensure adequate sealing and proper use of audit trail information, Notices of Approval should provide sealing plans and detailed audit trail operating instructions, including how to enter and exit the audit trail, for each approved model of device.
3.0 Indication and Registration - Representation
Reference: Sections 3, 5, 6, 7, 30 to 38 of the Specifications.
The Specifications require that devices be provided with indicating and recording elements appropriate in design and amount, and that indications and recorded representations be clear, definite, accurate and easily readable under normal conditions of use of the device. There are several requirements that must be satisfied to facilitate the reading and interpretation of displayed weight values, while other requirements address the proper operation of indicating and recording elements.
3.1 Value of d and e
3.1.1 The maximum and minimum number of scale intervals must comply with section 3 of the Specifications.
3.1.2 The value of "d" (and "e") must be equal to 1 x 10x, 2 x 10x or 5 x 10x of a legal unit of measurement (kilograms, grams, milligrams, pounds), where x is a negative or positive whole number, or zero.
3.1.3 The value of "d" (and "e") of analogue indicating devices may be equal to 1/2n of a pound, ounce or any other Canadian whole units, where n is a positive whole number (1/2, 1/4, 1/8, 1/16, 1/32 pound, ounce).
3.1.4 For Class III, III HD and IIII devices, for multi-interval devices and multiple range devices, "e" must equal "d".
3.1.5 On Class I or II devices, other than a multiple range or multi-interval device, "e" may be larger than "d", and must be the value of the scale division immediately preceding the auxiliary reading means.
3.1.6 On a digital indicating device, if "e" is different from "d", "d" must be clearly differentiated from the other figures.
Acceptable solutions1. The last digit ("d") may be shaded.
2. The last digit ("d") may appear in brackets.
3. The last digit ("d") may be smaller and set apart.
3.2 Legible, readable and non ambiguous
3.2.1 Indications and registrations of weights, prices, etc. must be designed and located so that reading the results is reliable, easy and unambiguous.
3.2.2 Digits must be uniform in size, shape and character (except if "e" ≠ "d").
3.2.3 Any indication of function or condition may not be represented in a manner that interferes with the interpretation of weight. For example, a "+" or "-" sign used as an over/under indication may not be placed adjacent to a weight value.
3.2.4 Except for postal scales, digital weight values must be in a single unit of measure across the weighing range. For any one indication of weight, only one unit of measure may be used.
3.2.5 Subordinate indications and recorded representations are appropriately designated or portrayed. A decimal point or a comma must be used to set apart decimal submultiple of the unit.
3.2.6 A digital device must display at least one digit to the left of the decimal point or comma, and all the digits to the right of the decimal point or comma. If a decimal point or comma is not used, at least one active decade plus any constant (fixed) zeros must be displayed. All decades to the right of a decimal point or comma must be active (no fixed zero).
Clarification:
| Capacity | Minimum zero indication | |
| 25 x 0.01 lb | 0.00 lb | |
| 5 000 x 1 lb | 0 | |
| 100 000 x 20 lb | 00 lb * The last digit is a fixed zero |
3.2.7 Displayed and printed values of gross, tare and net must be in the same units.
3.3 Video display terminal
3.3.1 If an indicator or a video display terminal provides the primary or the only weight indication for the scale when in the weighing mode, the weight display must be a continuous live display, in an area dedicated to the weight display, and clearly distinguished and separated from other information on the display.
3.4 Analogue Representation - dials, beams, poises, etc.
3.4.1 Scale marks (length, width and spacing) and indicators (pointers) must be designed and assembled so that reading the weighing results is easy and unambiguous. The overall inaccuracy of reading shall not exceed 0.2 e (OIML R 76-1 section 4.2.1).
The following are recommended minimum design requirements to ensure accuracy of reading, and overall accuracy of the device (compliance to 3.4.1).
Scale Marks
3.4.1.1 Scale marks must consist of lines (graduations) of equal thickness; the width or thickness of the lines must be constant, not less than 0.2 mm and not larger than the space between the lines.
3.4.1.2 Lines must vary in length to facilitate readings. The length of the shortest lines must be equal or longer than the width of the clear space between the lines.
3.4.1.3 The distance between the main scale marks must be uniform to ensure a linear indication across the scale.
3.4.1.4 The clear space between lines must be at least 0.75 mm.
Numbering
3.4.1.5 The scale interval of numbering must be constant and should not be greater than 25 times the scale interval of the device.
3.4.1.6 If the scale is projected on a screen, at least two numbered scale marks should appear in the projected zone.
3.4.1.7 The height and width of the numbers (real or apparent) should be proportional to the scale marks and so that the reading of the weighing results is easy and unambiguous.
Indicator (pointer)
3.4.1.8 The width of the pointer must not exceed the width of the graduation lines and the width of the clear space between weight graduations.
3.4.1.9 The portion of the pointer that extends along the length of graduation lines and that may be brought into coincidence with the lines must be of the same width.
3.4.1.10 The length of the pointer must be such that the tip is at least level with the middle of the shortest scale mark. If the pointer and the scale marks are in the same plane, the distance between the tip of the pointer and the end of the graduation lines must not exceed 1 mm.
3.4.1.11 Parallax effects must be reduced to the practical minimum. The clearance between the pointer and the scale marks should in no case exceed 1.5 mm.
Weighbeams
3.4.1.12 The scale marks (graduations) must consist of lines of equal thickness. The distance between graduations should not be less than 2 mm so that the normal machinery tolerance for notches or scale marks do not cause errors in the weighing results exceeding 0.2 e.
3.4.1.13 Graduation should be perpendicular to the beam.
3.4.1.14 The normal balance position of a weighbeam must be horizontal; the weighbeam must have equal travel above and below the horizontal. The total travel distance between trig loops and between other limiting stops near the weighbeam must be sufficient to ensure accurate reading. The following minimum distance are recommended:
| Distance from the weighbeam fulcrum to the limiting stops (centimetres) | Minimum travel between the limiting stops (millimetres) |
|
30 or less +30 to 50 +50 to 100 more than 100 |
10 13 18 23 |
3.4.1.15 A shoulder or a stop shall be provided on each weighbeam bar to prevent a poise from travelling and remaining back of the zero graduation.
Poises
3.4.1.16 No part of a poise (including the locking screw) shall be readily detachable. The adjusting material in a poise must be securely enclosed and firmly fixed in position and must not be in contact with the weighbeam. There must be no cavity that could accidentally hold foreign bodies.
3.4.1.17 A sliding poise, other than a hanging poise, on a notched weighbeam bar must have a pawl that will seat the poise in a definite and correct position in the notches, wherever in the notch the pawl is placed, and hold it there firmly and without appreciable movement.
3.4.1.18 Sliding poises must be provided with an indicating component. The indicating component of a poise must be sharply defined and the reading edge shall be parallel to the graduation lines.
Counterpoise Weights
3.1.4.19 Counterpoise weights shall comply with the requirements prescribed by sections 20, 72, 73, 77, 78 and 79 of the Weights and Measures Regulations.
4.0 Recorded Representation (Printed)
Reference: Sections 30 to 38, 66 and 67 of the Specifications.
The recording element (printer) of a device shall be appropriate and compatible with the device. Recorded representations must be clear, definite, accurate and easily readable. The interfacing of a printer to a device must not cause any alteration or degradation of the metrological characteristics of the device and must not facilitate the perpetration of fraud. The following are requirements that apply to printers and printed tickets.
4.1 All recorded values shall be permanent, legible and printed in digital format.
4.2 The device must indicate and print weight values in the same unit of measurement.
4.3 The value of d printed and the value of d displayed must be the same (except for postal scales and weight classifiers)
Added May 10, 1999.
4.4 The value of d printed may be larger than the value of d displayed by a weight classifier provided that the measurement, the weight classification and the pricing are accurately determined. Tests must be performed at the turning points of price ranges (see part 6.0).
4.5 Except for weight classifiers, a printer must record the same value and number of decimal places as indicated on the display.
Clarification:
A digital indicator may display weight values in 0.005 kg and 0.01 lb scale intervals. The printer must therefore record weight values to 0.005 kg in metric and 0.01 lb when measuring in pounds. It may not record weight values to 0.010 lb.
4.6 All recorded weight values, such as gross, tare, net, inbound and outbound weights, shall be clearly identified using acceptable words, abbreviations or symbols (see Appendix 2-A ).
However, if only one weight is printed, it does not have to be identified as the "net" weight.
Modified May 10, 1999
4.7 If the unit of measurement of the device can be externally selected by the user (lb/kg switch), the printer must record the proper unit of measurement along with the weight values. Preprinted tickets stating the weight unit are acceptable for indicators capable of displaying one weight unit only or which have an internal lb/kg switch.
Modified May 10, 1999
4.8 Computation must be in mathematical agreement (gross weight - tare weight = net weight; unit price x net weight = total price, rounded off to the nearest cent).
Price computing devices
4.9 Unit prices must be printed when total prices are shown and both have to be clearly identified as the unit price and the total price.
Point of sale (POS) weighing systems
Definition:
a weighing element or a non computing scale interfaced with an electronic cash register or computer. Usually, the cash register or computer reads the gross weight provided by the scale, assigns a tare through a PLU code and prints a net weight on the cash register tape. The cash register must not interfere with the operation of the scale. A stand alone price computing scale used in conjunction with an electronic cash register would not fall into this category.
4.10 The cash register tape must provide the information required by section 67 of the Specifications. That is, the net weight, the price per unit, the computed price, and the appropriate identification code or product name. Furthermore, in order to standardize content and layout, as well as adding clarity to POS receipts, it is recommended that the rules and the example found at the end of this section be followed. Please note that the identification code/product name has been left out of the example for clarity; this information is however required on actual POS receipts.
Note:
A POS system may display the Gross weight on the scale display and the Net weight on the cash register display; however, it must print the Net weight on the cash register tape. The scale of a POS system is not required to display the net weight nor provide an indication that a tare value has been entered.
Training mode is no longer required on POS systems.
Weight Classifiers
4.11 In the case of weight classifiers, it is acceptable if the printed ticket provides the weight only or the weight along with the total price to be paid. The unit price is not necessary since the total price to be paid is determined on the basis of weight ranges within the device's weighing capacity rather than on the basis of a price per unit.
Point of sale (POS) receipts
| I | II | III | IV | V |
| 1.000 | kg or lb | @ | $ | 12.49 |
|
Must be identical to the scale display (interval size and capacity limitation) Must print a zero before the decimal point if the weight is less than 1 kg or lb A period or comma can be used as the decimal point |
Must be lowercase letters The use of "lbs" or "#", as the symbol for pounds, is not acceptable |
Can be replaced by: "at" ("à" in French) |
Must be placed before or after the value in column V |
Must be two digits after the decimal point Must be preceded by a zero, before the decimal point, if the value is less than one A period or comma can be used as the decimal point |
| VI | VII | VIII | IX |
| / | kg or lb | $ | 12.49 |
|
Can be replaced by: "per" ("par" in French) |
Must be lowercase letters The use of "lbs" or "#", as the symbol for pounds, is not acceptable |
Required if there is only 1 space between columns VII and VIII Optional if there are two or more spaces between columns VII and VIII Can be placed before or after the value in column IX |
Must be two digits after the decimal point Must be preceded by a zero, before the decimal point, if the value is less than one A period or comma can be used as the decimal point |
* Note: Product identification code/name is also required
Spacing:
- A space is required between columns I and II (due to the use of "lb")
- At least 1 space is required between columns II and III
- At least 1 space is required between columns III and IV
- No space between columns IV and V, regardless of whether the "$" is placed before or after the "12.49"
- A space between columns V and VI is optional if the slash "/" is used. If the word "per" ("par" in French) is used then a space is required
- A space between columns VI and VII is optional if the slash "/" is used. If the word "per" ("par" in French) is used then a space is required
- At least 1 space is required between columns VII and VIII
- No space between columns VIII and IX, regardless of whether the "$" is placed before or after the "12.49"
Reference: Section 35 of the Specifications
Graduations, indications, and recorded values that are intended to have specific values as well as metrologically significant annunciators must be adequately identified by suitable words, abbreviations or symbols. These defining terms must be placed relative to graduations, indications, recorded values or annunciators and as close as practical to them without interfering with their readability. The proper symbols for SI units are found in Schedule I of the Weights and Measures Act; other acceptable abbreviation or symbols can be found in Appendix 2-A of this manual.
5.1 Graduations, weight indications must be properly defined by appropriate figures, words or symbols (lb, kg, ounces, tare, net weight, etc..).
5.2 Annunciators that are metrologically significant are defined with appropriate words or symbols.
Clarification:
1. Only metrologically significant annunciators are required to be identified, namely:
- Unit price display
- Total price display
- Gross, Tare and Net displays and annunciators
- Center of zero annunciator
- lb/kg unit annunciator
- Scale selection annunciator on a muti-platter device
- Other annunciators required in this Manual
2. The metrological annunciators may be identified using durable labels except when the annunciator must be capable of changing automatically to reflect a change of status (Examples: Tare on/off, center of zero yes/no, lb/kg, etc.)
3. The position of the lb/kg toggle switch is not a sufficient indication of the unit in use.
5.3 Gross weight, Tare Weight and Net Weight, Inbound/Outbound Weight, Unit Price, Total Price and other required information must be adequately identified by names, abbreviations or symbols.
5.4 The names, abbreviations and symbols are suitably located.
5.5 If the device has an external key or switch (user key) to change the measurement unit (lb/kg), the printer must automatically print the appropriate unit of measurement.
5.6 The external user key or switch of a device must automatically change the measurement units (lb/kg key) associated with indicated and printed gross weight, tare and net weight.
Clarification:
1 If the device can operate only in a single unit of measurement, it is acceptable that the symbol or name identifying the unit of measurement is pre-printed on the ticket rather than printed by the device.
2. If only one weight value is printed, it is assumed that it is the net weight. In such a case, identifying the weight as to be the net weight is not required.
6.0 Agreement of Registrations
Reference: Section 18 of the Specifications.
LG-6.01 Test for the agreement of registrations
Purpose
The purpose of this test is to establish the accuracy and reliability of communication among all means of indication and registration of a device. The means of indication and registration include primary and secondary indications, printers, computers and other recording means.
Application
This test is applicable when a device is equipped with two or more means of registration that register in the same units of measurement (i.e., primary indicator, secondary indicator, printer, etc.). The test applies to mechanical analogue devices and electronic digital indicating devices. If the device (or weight indicator) can be interfaced to a printer, a compatible printer must be attached to the device for the test.
The following test must be performed for each unit of measurement that the device can display.
Test Procedure
- Zero the device.
- Verify the agreement between indications and registrations at zero load (or the minimum load that can be printed).
- Apply a load to the load receiving element and print.
- By 1d steps, increase the load on the load receiving element by 10d, noting the registrations (including the printouts) at each step.
- Repeat the test with different loads (e.g., close to zero load, at mid capacity, close to capacity).
- Verify the agreement of all indications and registrations, including the printouts.
Interpretation of Results
Weight indications and registrations must agree within the limits prescribed by the Specifications. The device complies with the requirements when the quantities indicated and/or printed are in agreement within the following limits:
1. Electronic digital values having the same value of verification scale interval must be in exact agreement;
2. Analogue values having the same value of verification scale interval must agree within 0.25 times the value of the verification scale interval;
Corrected May 10, 1999
3. Mechanical digital values, electronic digital values having different verification scale intervals, and combined digital and analogue values must agree within 0.6 times the value of the largest verification scale interval.
The agreement of registration requirements are applicable when indications and registrations of weight values are in the same weighing mode (net, gross or tare). Indicated and registered net weights must therefore agree, within the above limits, as must indicated and registered grossweights and indicated and registered tare weights. However, this requirement is not intended to apply when a device indicates a gross weight and prints a net weight, as is the case with some POS systems.
Added May 10, 1999
The indication of a gross weight and the printing of a net weight is acceptable on POS systems as well as weighing systems used in applications other than direct sales to the public.
Added May 10, 1999
Weight Classifiers
The verification scale interval of a printing device (i.e., printer, computer) may be larger than the verification scale interval of the weight classifier to which it is interfaced. In addition to the "agreement of registration" test described above, a test at the turning points of price ranges is performed to ensure that in all circumstances packages are classified accurately.
| Example | Weight classifier 10 kg x 5 g | |
| Printing device with a scale interval of 10 g Price ranges: 0 - 30 g (included)= $1.00 |
||
| More than 30 g = $2.00 | ||
- Apply a load so that the weight indication is 25 g.
- Print the weight and price. The ticket may print 20 g or 30 g, and must print $1.00.
- Apply a load so that the weight indication is 30 g.
- Print the weight and price. The printed weight must be 30 g, and the price must be $1.00. Modified May 10, 1999
A weight of 40 g and a price of $2.00 (second price range) may not be printed before the weight classifier indicates 35 grams.
LG-6.02 Suitability of unit conversion
Purpose:
To uncover registration errors resulting from an inadequate unit conversion mechanism. This type of error is found when a DUT internally calculates a mass indication in a unit of measurement prior to converting it, rounding it off and registering it in a different unit of measure.
Application:
To all DUT capable of indicating in a metric and in a non-metric unit of registration.
Test Procedure:
A. For each of the units of measurement in which the DUT is capable of registering, perform step B. and C.
B. Set the DUT to register in the unit of measurement being verified.
C. At least fourteen times, add a test load equal to e and each time, record the registration.
Interpretation of the Results:
The DUT is deemed to meet the requirements if for each unit of measurement tested, the registration did not skip any steps.
Clarification:
1. Under section 39 of the Specifications, indicated and printed representations of Net, Gross and Tare weights of a device must have the same value of verification interval e for any given load.
2. In the case of a secondary indicating element intended to duplicate, for the benefit of consumers, the information displayed by the operator's indicating element, the registration on both displays must be in the same graduation size and in the same unit of measurement. Furthermore, the printed registration intended for the consumers must be exactly as the indicated registration (e.g same graduation size and same unit of measurement).
3. An indicating element and a printer used in conjunction must at least register in the same unit of measurement. Supplementary information in other units of measurement may be provided by the indicator and/or printer.
4. A device may display weight values in two units of measurement simultaneously.
5. All weight indications and registrations must be within tolerances.
Reference: Sections 19, 30 to 35, 46 and 47 of the Specifications.
7.1 Price computing devices must print the unit price when the total price is printed.
7.2 Displayed and recorded monetary values must comply with applicable requirements of section 3, Indication and Registration Representation, and of section 5, Values Defined in this Guide (e.g. Value of d, legible and readable, number of digits, decimal representation, defining words and symbols, etc.).
7.3 Devices intended for direct sale to the public:
7.3.1 Devices must display the unit price when the total price is displayed.
7.3.2 When the device displays in kilograms, the unit price that can be entered and displayed is limited to Price/100 g and Price/kg.
7.3.3 When the device displays in Canadian units, the unit price that can be entered and displayed is limited to Price/pound.
7.3.4 When a device displays weight values on the basis of the gram or ounce, unit prices may also be entered and displayed on the same basis.
Examples:
1. A 2500 g x 1 g scale displays 1.5 kg as 1500 g. This scale displays weight values on the basis of the gram. Such a scale may display a price per gram.
2. A 5 kg x 0.001 kg displays 1.5 kg as 1.500 kg. This scale displays on the basis of the kilogram. The unit price that can be entered and displayed by that scale is limited to Price/kg and Price/100 g.
7.4 The Total Price Display Unit must have enough digits to indicate the computed total price on the basis of the maximum load that the device can weigh times the maximum value of unit price that it can accept.
Clarification:
The maximum unit price that can be entered is $99.99/kg and the maximum weight is 10.005 kg. Then, if if a unit price of $99.99/kg can be entered, the total price display must have enough digits to display $1004.90 (6 digits).
7.5 The total price must be calculated accurately and rounded to the nearest one cent, by multiplication of weight and unit price, both as indicated by the device. Perform the test described in LG-7.01
7.6 When the displayed weight is less than zero, the device must not be capable of displaying or printing a computed total price. Place a small load on the platter, tare it and remove it from the platter. A negative weight value should be displayed. Attempt to enter a unit price. Attempt to print this value.
7.7 When the scale indicates an overcapacity condition, the device must not be capable of displaying or printing a weight and/or computed total price.
7.8 The displayed weight and total price must be free floating, that is when the scale display a unit price, a weight and a total price, if the weight or the unit price is changed the total price must change accordingly.
Free Floating Signal
Purpose
To ensure that the displayed net weight and total price are free floating. That is when the scale displays a unit price, a weight and a total price, if the weight or the unit price is changed, the total price must change accordingly.
Procedure
Price computing scale
- Place a load on the platter.
- Enter a unit price; a total price is now displayed. Ensure that the indicated monetary value is in mathematical agreement with the weight and unit price to the nearest cent.
- Increase the load on the platter; the total price must increase accordingly.
Scale equipped with a tare display
- Enter a Keyboard or a platter tare value.
- Place a load greater then the value of the tare; the scale displays a gross weight, a tare weight and a net weight.
- Ensure that the gross, tare and net values are in exact mathematical agreement.
- Change the tare value; the net weight should change accordingly.
POS systems
- Determine the keying sequence necessary to cause the device to compute a final price.
- Place a load on the platter
- Key in the complete sequence except the last keystroke required for price computation.
- Change the load on the platter.
- Operate the final keystroke to initiate price computation.
Interpretation of Results
7.9 The device complies with the requirements if:
- in all circumstances, mathematical concordance is maintained; and
- in the case of a POS system, it computes total prices using the load on the scale at the time the final key was pushed, or produce an error signal, or lock out to prevent any price computation.
LG-7.01 Agreement of registration of monetary values
Purpose:
To determine if the scale computes accurately and rounds the values of total prices correctly.
Application:
Applicable to any price computing scales and POS systems.
Test Procedure:
A. Apply several loads to the scale and enter different prices
B. With a calculator determine the correct values, round them off to the appropriate decimal, and compare them to the total price indicated by the scale.
C. The following are suggested loads and unit prices:
| Test # | Net Weight (kg) | Unit Price | Total Price | Correct Indication |
| A | 0.01 | $4.54 | $0.04540 | $0.05 |
| B | 0.01 | $4.55 | $0.04550 | $0.05 |
| C | 0.01 | $4.90 | $0.04900 | $0.05 |
| D | 0.01 | $5.10 | $0.05100 | $0.05 |
| E | 0.01 | $2.50 | $0.02500 | $0.02 or $0.03 |
| F | 0.01 | $2.51 | $0.02510 | $0.03 |
| G | 0.651 | $0.76 | $0.49476 | $0.49 |
| H | 0.652 | $0.76 | $0.49552 | $0.50 |
D. Apply the following rounding rule:
| Computed Results | Correct Indication |
|
0.020 |
0.02 |
Interpretation of Results:
The monetary registration is correct if for a net weight (as outlined in the "Net Weight" column in the above table) and a unit price (as outlined in the "Unit Price" column in the above table) yields the corresponding indication (as outlined in the "Correct Indication" column in the above table).
8.0 Recorded Representation of Gross, Tare and Net Weights
Reference: Sections 19, 30 31, 32, and 33 of the Specifications
There are two primary requirements concerning the printing of weight values. First the recorded values must be mathematically correct and, second, the recorded values must be in agreement with the displayed values.
Two situations provide the greatest potential for non compliance with these requirements. One is when a platter tare is taken to the internal resolution of the scale and the scale indicates and records Gross, Tare and Net weights. In the second, a scale sums the analog signal from two or more weighing elements and the scale indicates and records Gross, Tare and Net weights.
LG-8.01 Agreement of registration of Gross, Tare and Net weights
Application:
The following procedure is performed on an electronic scale when a tare is taken to the internal resolution and the scale can display and/or print Gross, Tare and Net weights.
A. Place a load on the platter that results in a scale indication that is just below the zone of uncertainty (or upper edge of the interval) and press the push-button tare key.
B. Add more weight to the scale so the gross load is just above the zone of uncertainty (lower edge of the scale interval).
C. Compare the indicated and recorded values for the Gross, Tare and Net weights. Values must be in mathematical agreement; indicated and printed values must be in agreement.
Example of possible non compliance on a 50 t x 10 kg
| Load perceived by the scale to the internal resolution | Displayed and Recorded Values |
|
45006 kg Gross |
45010 kg Gross |
The following procedure is performed on an electronic scale that sums the analog signals from two or more weighing elements and the scale displays and prints Gross, Tare and Net weights.
A. Place a load on each weighing element that results in a weight indication just below the zone of uncertainty (upper edge of the scale interval), or just above the zone of uncertainty (lower edge of the scale interval).
B. Compare the indicated and recorded values for the Gross, Tare and Net weights. Values must be in mathematical agreement; indicated and printed values must be in agreement.
Examples of possible non compliance on a 300 kg x 0.1 kg scale
| Load to internal resolution | Displayed values | Load to internal resolution | Displayed values | |
| Scale 1 | 25.04 kg | 25.0 kg | 25.06 kg | 25.1 kg |
| Scale 2 | 25.04 kg | 25.0 kg | 25.06 kg | 25.1 kg |
| Sum | 50.08 kg | 50.1 kg | 50.12 kg | 50.1 kg |
Interpretation of Results:
8.1 The device complies with the requirements if the displayed and printed values of Gross, Tare and Net weights are in mathematical agreement (N + T = G); and displayed values agree with printed values.
9.0 Manual Entries of Gross Weight
Reference: Sections 30, 31, 32, 33 and 38 of the Specifications.
This section does not apply to keyboard tare entries (see section 17.0 for tare requirements).
Metrological features of a device used in trade must be of such design, composition and construction so as to ensure accurate measurement and minimize the potential for fraudulent use. Many devices incorporate features that allow the operator to enter a weight value through a numeric keypad or keyboard. This weight value can be displayed and/or printed with no load on the load receiving element.
Manual weight entries may be necessary in certain circumstances, such as POS systems, when credit must be given, or when generating labels for standard packages or correcting erroneous tickets. However, this capability may increase the potential for fraudulent device use if it is permitted without suitable precautions.
Manual weight entries can therefore be allowed under the following conditions:
9.1 The scale must be at gross load zero (load receiving element empty) and the scale indication must be at zero in the gross weight display mode before manual weight entries can be made.
9.2 The device must be incapable of weighing when it is processing or printing a manual weight entry.
9.3 Displayed and printed manual weight entries must be adequately defined and must be automatically identified as "Manual Weight", "Manual WT" or "MAN WT" ("poids manuel", "pds manuel" or "PDS MAN").
Clarification:
1. When a manual weight entry is printed and automatically identified as such, displaying the manual weight value is optional. If, however, the manual weight value is displayed, it must be properly identified as such.
2. Identification of a manual weight entry, with the proper term, must be done automatically without the need for operator intervention.
3. The use of a symbol to identify multiple manual weight entries is permitted provided that the symbol is defined on the same page as that on which the manual weight entries appear and the definition of the symbol is automatically printed by the recording element as part of the document.
4. The following symbols are not acceptable: MAN, MW
9.4 Manual weight entries must be an optional feature that can be enabled/disabled and sealed against use in applications where their use is inappropriate and could facilitate fraud.
10.0 Indicating Zero and Negative Values
Reference: Sections 30 to 33, and 41 of the Specifications.
The purpose of the following requirements is: to ensure that devices can be set and maintained as close as possible to a true zero value; to eliminate possible confusion between under and over indicated weight values; and to ensure that the smallest value of scale interval for digital devices remains an adequate representation of device accuracy.
Indicating zero
10.1 The device must be provided with means to adequately indicate or record a "zero-balance" condition.
10.2 Automatic indicating devices must provide an out-of-balance indication on both sides of zero.
Clarification
- Over/Under Indicators At least one graduation on each side of the zero reference must be provided. Clear indication must be provided to differentiate between the below zero and above zero portions of the chart.
- Digital The minimum acceptable indication of a zero balance condition must be one of the following:
- if a decimal point or comma is used, at least one digit to the left and all digits to the right of the decimal point must be displayed;
- if a decimal point or comma is not used, at least one active decade plus any constant (fixed) zeros must be displayed;
- all decades to the right of a decimal point must be active, i.e. a fixed zero cannot appear to the right of a decimal point.
| Examples: | Max x d (kg) | Minimum Zero Indication |
| 25 x 0.01 | 0.00 | |
| 5000 x 1 | 0 | |
| 50 000 x 10 | 00* | |
| * The last digit may be fixed. | ||
In the case of an electronic digital display, the zero balance indication may be a continuous digital weight indication or be indicated by other means provided that the scale either automatically inhibits the scale operation or returns to a digital weight indication when an out-of-zero balance condition exists (See section on sleep mode).
10.3 A digital indicating scale must either automatically maintain a "center-of-zero" condition to ± 1/4 of e or less (AZSM) or have a center-of-zero indicator that defines the zero balance condition to ± 1/4 e or less. Class I or II devices with auxiliary indicating means must define a zero balance condition to ± 1/2 d only. Therefore, these devices are not required to have a center-of-zero annunciator or an AZSM. Perform test LG-15.01.
Clarification: If the zeroing range of AZSM is less than the width of zero ( ± 0.4 d ), then a center of zero indication that defines the zero balance condition to ± 1/4 d or less is required. Otherwise the scale could possibly display zero and not be truly set to zero within ± 1/4 d. In this case, the operator would not be warned that the device needs to be re-zeroed.
10.4 If provided, the center-of-zero indicator must be inhibited at all displayed weight values other than zero ± 1/4 e (or 1/2 d for class I or II devices with auxiliary reading means).
10.5 On digital indicating devices, a + or - sign must not appear when the scale is indicating zero in any of the available units.
Displaying negative values
10.6 A display of negative value is required in the Net display mode when the Gross weight is less than the Tare value.
10.7 A negative value must be indicated in a manner that cannot be confused with a positive weight value. A minus sign clearly associated with the weight indication may be used provided that it is located in a manner that does not interfere with the weight.
10.8 Blanking the display is a method that may also be used to indicate an under-zero condition when the device is in the Gross mode (no tare); the scale may also display symbols which cannot be interpreted as a quantity value (e.g. EEEEEE, Underload, S-1, etc.). A row of zeros, flashing zeros or flashing weight values are not acceptable means.
Notes:
1. For devices such as hopper or tank scales, it is recommended to indicate a negative balance condition and an over-capacity condition differently so that the load condition is evident for the operator.
2. For devices such as hopper or tank scales, if blanking the indication is used, it is also recommended that the indicator has an annunciator to indicate "power on" so the operator does not think that the power has been lost when the display is blank.
Sleep Mode or Displaying Non Metrological Information
Definition: "sleep mode" means a function of a device that blanks partially or totally indications after a defined period of non use, in order to save the screen or to display information other than weights.
A device may go in a sleep mode or may display non metrological information such as advertisement, greetings, time and date, etc. provided that the following conditions are met:
10.9 The scale totally or partially blanks its indications or displays non metrological information only when the device is at Gross load zero (no tare) and has reached a zero-balance condition.
10.10 If the device blanks its indications partially only or displays non metrological information, the displayed information cannot be construed as weight indications.
10.11 The scale must be provided with an automatic means to inhibit the weighing operation or return the device to a continuous digital indication when the scale is in an out-of-balance condition. Perform the test described in LG-10.01
10.12 Printing function must be inhibited when the device is in sleep mode.
Alternative
A scale may go into "sleep mode" with a load on the platter, if the scale is designed to prevent any further weighing operation before the load is removed from the platter, all tares are cancelled and the device is reset to zero.
In this case the device must bear a special legend " The scale is set to zero when in the sleep mode" (or similar message) adjacent to the weight display for the customers' view.
LG-10.01 Means of Automatically Restoring Weight Indication
Application
This test will be performed on any electronic device with a sleep mode or capable of displaying non metrological messages.
Purpose
To ensure that the device has means of detecting when it is no longer in a zero-balance condition and restoring a weight indication; and also to ensure that the printing function is inhibited when in sleep mode.
Test Procedure
- Ensure that the "sleep mode" function is activated;
- Zero the device and wait until the device goes to the "sleep mode" or display non metrological messages;
- In one firm motion (so as to prevent the AZSM from capturing part of the test load) apply a load equal to d. The non-zero/non-metrological registration must have been replaced by a mass registration equal to d;
- Wait 5 minutes (or the normal delay for the device to return to the sleep mode) to see if the device will go into a "sleep" mode with a load on the platter;
- Zero the device with the load on the platter and wait until the device goes to "sleep mode" or display non metrological messages;
- Attempt to print;
- In one firm motion, remove the 1 x d test load. The device must display a mass of - d, or provide an under-weight indication.
Interpretation of the Results
The device complies with the requirements if:
- it does not go into a "sleep" mode when there is a load on the platter;
- it returns to a weight indication when an off-zero condition exists; and
- the printing function is inhibited.
11.0 Load Receiving/Weighing Element
Reference: Sections 30 to 33 of the Specifications.
Scales used to weigh wet commodities such as fish, lobster, etc. are required to have a load-receiving element, generally a scoop or platform with raised edges, to effectively drain off liquid that would tend to accumulate on the scale. This requirement does not apply to small computing scales such as those used in supermarkets since few wet commodities are weighed. In those particular applications, the scoop or platter can be easily removed and cleaned to maintain the zero balance condition.
11.1 If the load receiving element is designed to received wet commodities, it must also be designed to drain effectively.
11.2 Tank or hopper scales and their associated piping or conduit must be designed to ensure proper drainage and complete delivery of products.
Scales must be designed such that the normal movement of load receiving elements (platform, pan, etc.) during use will not "bind" and interfere with the weighing operation. This is checked by shifting the load receiving element when loaded. Mechanical systems must be designed to reduce frictions.
11.3 The load receiving/weighing element is designed to remain centrally aligned under load; lateral movements of the platter or platform do not cause bindings or frictions that interfere with the weighing operations.
If a device has a locking feature, this feature must only have two stable positions corresponding to "lock" and "weigh" (no intermediate position), and weighing must only be possible in the "weigh" position. Electronic digital devices must "blank" and inhibit printing in the "locked" position.
11.4 The device locking feature (if any) has only two positions: "locked" and "weigh".
11.5 Weighing is possible only in the "weigh" position, and the locking feature does not interfere in any way with the weighing operation.
11.6 Overload protection (stoppers) must be set so that they do not interfere with weighing operation.
12.0 Load Cell - Relationship of VMIN and d
No requirements for the time being
13.0 Damping Means and Up-Dating Rate of Weight/Price Data
Reference: Sections 30 to 33 of the Specifications
The weight indications must stabilize shortly after a load is applied to the scale. Weight indications must not oscillate significantly or update so slowly that intermediate weight values are misinterpreted as the final stable weight value. Weight indications, unit and total computed sale prices, after the weight indication is stable and after introduction of unit price, must remain visible while the load is on the platter to allow proper reading of the values.
Acceptable Solutions:
- On a mechanical device, damping should achieve a stable indication after three to five half periods of oscillation.
- For digital electronic devices, after a change in load, the previous indication should not persist for longer than 1 second.
- (OIML criteria) On a price computing scale, indication of weight, unit price and total price should remain visible for at least 1 second after the weight indication is stable and after introduction of a unit price while the load is on the platter.
- (OIML criteria) After the removal of the load, the indications may remain visible for no more than 3 seconds provided that the indication has been stable before and the indication should otherwise be zero. As long as there is a weight indication after removal of the load, it must not be possible to enter or change a unit price. Computed prices may remain visible while the platter is empty provided that this does not lead to confusion, measurement errors or fraud.
13.1 The mechanical device is equipped with an effective means for damping oscillations.
13.2 The electronic device up-dates the displayed weight information at a sufficient rate to prevent misinterpretation of the final weight value.
13.3 Indications of weight, and if applicable unit and total prices, are visible and stable when he load is on the platter.
13.4 A digital computing scale may continue to display computed price information following removal of the load provided that:
13.4.1 it does not display computed price information for more than 15 seconds (hold period);
13.4.2 it returns immediately to its zero weight reference;
13.4.3 it must automatically return to a "non-hold" or active mode at any time a new unit price is entered or the next load is placed on the platter;
13.4.4 it must return to an active mode and print the correct weight and price information for the current load conditions if it initiates label printing or a "print command" is given during the "hold" period.
Reference: Sections 30 to 33, and 40 of the Specifications
Weighing devices shall neither indicate nor print weight values in excess of their maximum rated capacities (Max). Perform the following test.
LG-2.05 Overload tests
Application
Applicable to complete electronic weighing devices and to separate electronic weight indicators. If the units of registration can be changed without having to perform a re-calibration of the device, then perform individual tests for each and every unit which the device is capable of registering.
Test Procedure
Span
- Stabilize and zero the device at nominal conditions;
- Load the device to its maximum rated capacity;
- Add loads until the device ceases to display weight values;
- Record the last weight value indicated (WI); attempt to print or transmit data to external ports at overload condition1.
- Repeat the test for other units of measurement that the device can display.
WI is less than or equal to≤ Max + (5% Max or 9e)
Tare features
F) Remove the load and set the device to zero.
G) Enter a keyboard or a platter tare (T) equal to approximately 20% of Max.
H) Add loads until the device ceases to indicate/print weight values
I) Record the last value indicated (WI)
WI + T is ≤ Max + (5% Max or 9e)
Note: Certain approved devices may incorporate a full or partial additive tare feature. An additive tare feature extend the weighing capacity of the scale. This must be taken into consideration when performing the blanking display test.
Zero (To be performed if the scale can zero loads in excess of 4%)
- Remove the load and set the device to zero.
- Add a load in excess of 5% of Max (say 20%); zero that load (Zl).
- Add loads until the device ceases to display/ print weight values; Record the last value indicated (WI)
- If the scale limits the amount that can be zeroed with a semi-automatic zero setting mechanism but the operation can be repeated several times, zero the maximum weight possible equal to or under 5% of Max. WI + Zl Ͱ4 Max + (5% Max or 9e)
Interpretation of Results:
14.1 The device is deemed to comply with the requirement if the device can not display or print weight values in excess of:
9 scale divisions, for computing scales other than weight classifiers and postal scales
or
105% of Max, for other scales
14.2 When over capacity, the device registration must blank within prescribed limits, or display a clear message that cannot be confounded with a weight value.
Acceptable Solutions:
1. Amongst others, the following means of indicating overcapacity are acceptable:
- a row of "EEEEEEE"
- a blank registration
- the word "Overcapacity"
2. Among others, the following means of indicating overcapacity are not acceptable:
- displaying a flashing eights
- displaying a row of zeros or eights
3. The same rules apply to printed information.
Reference: Sections 30 to 33, 40, 41, 42, 43 and 44 of the Specifications
There are several requirements that establish the proper operation of zero setting mechanisms to ensure accuracy and to prevent the perpetration of fraud or inadvertent measurement errors. These requirements depend upon the type of zero setting mechanisms and applications.
Definitions
Manual Zero-Setting Mechanism (MZSM): mechanism for setting the indication to zero by the operator (balance ball or potentiometer).
Semi Automatic Zero-Setting Mechanism (SAZSM): mechanism for setting the indication to zero automatically following a manual command (Push-button Zero).
Automatic Zero-Setting Mechanism (AZSM): mechanism for maintaining the zero indication within certain limits, automatically.
Initial Zero Setting Mechanism (IZSM): mechanism for setting the indication to zero automatically at the time the device is switched on and before it is ready to use.
15.1 Manual Zero-Setting Mechanism (MZSM)
15.1.1 If the balance at zero-load is achieved by the addition of supplementary material, the material must be enclosed in a cavity covered with a screw cap (or a cover with screws, etc.) so that it cannot be readily removed or altered and so that it cannot shift position in such a way that the balance condition of the device is affected during weighing operation.
15.1.2 If a device is provided with a balance ball and a captive screw or nut arrangement, the maximum effect must not exceed 4 verification intervals per revolution, and means must be provided to ensure sufficient friction to prevent a zero change during weighing operation.
15.1.3 A device intended for direct sales to the public may not be fitted with a MZSM unless operated only with a detachable tool .
15.1.4 The total range of zero setting (positive and negative portion) may not exceed 4% of the device capacity unless the gross load that can be weighed is not increased beyond the device capacity limit.
15.2 Semi Automatic Zero-Setting Mechanism (SAZSM)
15.2.1 The SAZSM must operate only when the scale provide a stable indication (See, Motion Detection, test LG-18.01).
15.2.2 A SAZSM (Push Button Zero) must set the indication to only zero, within ± 1/4 e. The SAZSM of a Class I or II device equipped with an auxiliary reading means must set the indication to zero to ± 1/2 d. Perform the test described in LG-15.01.
15.2.3 The activation of SAZSM must not clear stored tare weight values. Enter a platter or keyboard tare and attempt to clear it by pressing the zero button when the platter is empty (zero or negative indication) and loaded (positive weight indication).
15.2.4 The total zero-setting range (negative + positive) must not exceed 4% of the device capacity. The range may exceed 4% of Max provided that the gross load that can be weighed is not increased beyond the capacity limits of the device. Perform the test described in
15.3 Automatic Zero-Setting Mechanism (AZSM)
15.3.1 The device AZSM must not re-zero (in one shot) a weight value in excess of 0.6 e. Perform the test described in LG-15.02.
15.3.2 The total zero-setting range (negative + positive) must not exceed 4% of the device capacity. The range may exceed 4% of Max provided that the gross load that can be weighed is not increased beyond the capacity limits of the device. Perform the test described in
15.4 Initial zero Setting Mechanism (IZSM)
15.4.1 The IZSM must set the device to zero within ± 1/4 e. The IZSM of a Class I or II device equipped with an auxiliary reading means must set the indication to zero ± 1/2 d. Perform the test described in LG-15.01.
15.4.2 Determine if the value that can be "zeroed" by the device IZSM exceeds 20%. Perform the test described in LG-15.04.
Record this value.
Clarification:
This information is needed to establish which procedure will be followed for certain performance tests. If the IZSM range does not exceed 20%, the performance tests are done once with the maximum dead load. If the range exceeds 20%, certain performance tests are performed twice: one with the minimum dead load, the second with the maximum dead load. Individual procedures described in Part III indicate to which value IZSM must be set.
15.4.3 The IZSM range of indicators tested and approved separately must not exceed 20%.
LG-15.01 Center-of-zero indication and setting zero within ± 1/4 e
Application:
Applicable to complete electronic scales and separate electronic indicators having SAZSM or IZSM or equipped with a "center-of-zero" indicator.
Purpose:
This test is to verify that the SAZSM and IZSM automatically set the device to zero within ± 1/4 of e, and to verify that the device range of center-of-zero indication is equal to or less than ± 1/4 e. Note that the range of center-of-zero indication of Class I or II devices equipped with auxiliary reading means is ± 1/2 of d. This must be taken into consideration when performing the following tests and interpreting the results. Take into account that the ZU of weight classifiers is adjacent to the graduation.
Procedure: Setting zero to within ± 1/4 e.
- Switch the AZSM off or set its value to zero effect; zero the DUT.
- Place a load of at least e (made of 1/10 e weights) on the platter and RE-ZERO the device.
- Successively remove small denomination weights in 1/10 x e steps until the low end of the interval is reached (the indication begins to alternate between 0 and -1 e). Record the weights removed as being the negative portion of the interval.
- Successively add small denomination weights in 1/10 x e steps until the high end of the interval is reached (the indication begins to alternate between 0 and +1 e). Record the value of the weights added and subtract the value of the weights recorded in C. The difference is the positive portion of the interval.
- Determine if the zero position as set by the SAZSM does not deviate from the true zero reference point by more than 1/4 e. Generally, the zero position, as automatically set by the SAZSM, should coincide with the zero reference point; in such a case, the negative range would equal the positive range. See illustration.
- Repeat the test by zeroing the device using the IZSM.
Width of the centre-of-zero indication (Annunciator)
- Switch the AZSM off or set its value to ZERO effect.
- Set the device to zero.
- Place a load of at least e (made of 1/10 e weights) on the platter; zero the DUT.
- Successively remove small denomination weights in 1/10 x e steps until the visual confirmation of zero goes off. Record the value of the weights removed as being the negative portion of the center of zero indication.
- Successively add small denomination weights in 1/10 x e steps until the center-of-zero indicator goes off (positive limit). Record the difference between the value of the weights remaining on the platter and the value of the weight recorded in J as being the positive portion of the center-of-zero indication.
Interpretation of Results
The DUT is deemed to comply with the requirements if the zero setting mechanisms automatically set the device to zero within ± 1/4 of e from the true zero reference point, and if the centre-of-zero annunciator indicate a zero balance condition within ± 1/4 e of the true zero reference point.
Note that for Class I or II devices with auxiliary reading means, the range is ± 0.5 d.
1 On some devices, under overload conditions data are not transmitted through the port for printer; however, they are transmitted through the other ports.
LG-15.02 AZSM - Maximum incremental load that can be zeroed.
Purpose:
To determine that the largest load that can be deposited monotonically (i.e., in one shot) on the device, while the DUT is at zero load, and zero is equal to or less than 0.6 x e.
Procedure
Check for the addition of small loads:
- Ensure that the AZSM is on; Zero the device
- Place a known test load "A" equal to or greater than "e" (e.g:10xe), plus a load "B" equal to 0.7x"e" on the device load receiving element.
- Remove known test load "A", wait at least 10 seconds to see if the device will automatically rezero test load "B".
- If the device did not zero test load "B", repeat with smaller test loads (0.6 e, 0.5 e, 0.4 e, etc) to determined the maximum positive AZSM range. Record the maximum value that the AZSM rezeros.
Check for the removal of small loads:
- E. Place a small known test load "A" equal to or greater than "e" (e.g. 10xe), plus a load "B" equal to 0.7 x"e" on the load receiving element.
- F. Re-zero the device.
- G. Remove all loads. A negative value ("A" + "B") should now be displayed.
- H. Place the test load "A" back on the device and wait 10 seconds. The device should not reset to zero.
- I. If the device resets to zero, repeat with smaller test loads "B" (0.6 e, 0.5 e, 0.4 e, etc) to determine the maximum negative AZSM range. Record the value.
Interpretation of Results:
The device is deemed to comply with the requirement:
If after step "C", the device does not rezero automatically when there is only 0.7 x e left on the load receiving element (it is allowed to rezero automatically when there is a load equal to or less than 0.6 x e).
and
if after step "H", the device does not rezero automatically when the load is only 0.7 x e short of zero (it is allowed to rezero automatically when there is an apparent negative load equal to or less than 0.6 x e).
Clarification
The software of the device may allow the AZSM range to be set to different values (0.1e, 0.2e, 0.5e, 0.6e, 1e, 3e, etc..). Technologists must ensure that the AZSM can be set at a value that is within the maximum permissible value, and sealed.
LG-15.03 Re-Zero range (Maximum total range of SAZSM/AZSM/MZSM)
Application:
Applicable to complete electronic scales, electronic indicators, and mechanical scales equipped with balance ball type of zero setting.
Purpose:
This test is used to determine whether the total range of the zero setting mechanism, other than the initial zero-setting mechanism, exceeds 4%. If the total range exceeds 4%, to ensure that the gross load that can be weighed is not increased beyond the capacity limit of the device.
The procedure depends upon the type of zero setting mechanism. On mechanical devices, the procedure is relatively simple.
Mechanical Devices (beam scales, dial scales, etc.)
Procedure
A. Place a load ( 8-10 % of Max) on the load receiving element.
B. Set the balance ball to the lowest setting (low end of the range) and note the indication.
C. Set the balance ball to the highest setting (high end of the range) and record the indication.
Interpretation of Results
The difference between the indications at the low and high ends must not exceed 4% of Max.
Electronic Digital Devices
On electronic devices, both the SAZSM and AZSM setting ranges must be determined. As illustrated below, in some scale designs, there is only one common parameter that limits the range over which both the SAZSM and the AZSM can function.
When so designed, it is relatively easy to determine the total range because one only has to find the SAZSM range using weights and then to confirm that the AZSM has also been disabled once the limits of the range have been reached. For this type of design, use: "Weight Method".
In other scale designs, there are two distinct range limiting parameters; one for the SAZSM and one for the AZSM. See illustration below.
It is then necessary to find the limits of the SAZSM range and then to find the limits of the AZSM range. The total range is then a sum of the two. Unfortunately, it is difficult to find the AZSM range using small weights (or at least, it would necessitate a great number of small weights). For this reason, for such devices, use : "Water Method".
Procedures:
Method 1: "Weight Method"
Determination of the negative portion of SAZSM/AZSM
- Place on the LRE a load approximately equal to 6% of Max. This load should be made up of several smaller weights allowing for the gradual withdrawal of the load.
- Activate the Initial Zero Setting Mechanism by switching the DUT "Off" and "On" (Note: on some devices, it may be necessary to unplug and replug the power cord in order to activate the IZSM). The DUT should then have zeroed the 6% load and display a zero registration.
- By successively removing loads and activating the SAZSM (i.e.; zero button), determine to the nearest d the maximum load that can be removed from the LRE while still allowing the DUT to perform a semi-automatic zeroing.
- Once the DUT no longer performs a semi-automatic zeroing (The scale is just below the low range of SAZSM), remove a load equal to 0.5e; wait few seconds. Remove an additional 0.5e. If the DUT's AZSM has not rezeroed the 1e (0.5e + 0.5e) (and thus the DUT is displaying a -1e registration), this will have confirmed that the SAZSM and AZSM both share the same range limit in the negative direction. Record the total amount of weights removed as being the negative portion of the Total Range of SAZSM/AZSM.
Note:
If the DUT's AZSM has rezeroed the 0.5 e load that was removed, and if the DUT appears to continue automatically zeroing additional 0.5 e loads upon removal, then the "Water Method" will be used to determined the AZSM range.
- Restore all weights removed (thus restoring the 6% of Max on the LRE) and rezero using the SAZSM. (The DUT should now be indicating a zero registration).
Determination of the positive portion of SAZSM/AZSM
- By successively adding loads and activating the SAZSM (i.e.; zero button), determine to the nearest e the maximum amount of load that can be added to the LRE while still allowing the DUT to perform a semi-automatic zeroing.
- Once the DUT no longer performs a semi-automatic zeroing, add an additional load equal to 0.5 e; wait few seconds. Add an additional load of 0.5 e. If the DUT's AZSM has not rezeroed the 1e (0.5 e + 0.5 e) (and thus the DUT is displaying a +1 e registration) this will have confirmed that the SAZSM and AZSM both share the same range limit in the positive direction. Record the total amount of weights added in "F" as being the positive portion of the Total Range of SAZSM/AZSM.
Note:
If the DUT's AZSM has rezeroed the 0.5 e load that was added, and if it the DUT appears to continue automatically zeroing additional 0.5 e loads upon removal, then the "Water Method" will be used to determined the AZSM range.
- The sum of the positive and negative portion is the total range of SAZSM/AZSM. If the sum exceed 4% of Max, proceed with the test : Zeroing to Capacity
"Water Method"Determination of the total range of AZSM in a positive direction.
- With the LRE empty, place an empty container on the DUT's load receiving element.
- Re-zero the DUT using the IZSM by switching the DUT "Off" and "On" (Note: on some devices, it may be necessary to unplug and replug the power cord in order to activate the IZSM).
Note: Example of test assembly in the determination of the range of semi-automatic zero setting mechanism. In order to minimize the impact of falling drops of water, it is permissible to place the tubing against the receiving container so as to allow the water to run from the tube to the side of the container.
- With weights, load the DUT so as to bring the scale to a load which is near the maximum load that can be re-zeroed using the AZSM (high end of the SAZSM range)(value determined in G). Re-zero the load using AZSM. The scale should indicate zero with a certain load on the platter.
- Drop by drop, slowly fill the container with water so that the AZSM will continuously rezero the weight of water being added. In this manner, continue filling the container until the registration changes from zero (which will indicate that the positive limit of the AZSM range has been reached).
- When the indication changes to a value other than zero (thus signalling that the total AZSM range has been exceeded), immediately stop the flow of water.
- The range of AZSM going in a positive direction is the sum of the test weights on the platter and the weight of the water accumulated in the container.
Determination of the total range of AZSM in a negative direction.
- With an empty LRE, Rezero the DUT (using the Push-Button zero).
- Place on the LRE a container "A" filled with a quantity of water approximately equal to 10% of Max (or greater) and a hose as shown below.
- Add a quantity of test weights approximately equal to between 3 and 4% of Max.
- Re-zero the DUT using the Initial Zero-Setting Mechanism by switching the DUT "Off" and "On".
- Remove the test weights so as to bring the scale to a load near the maximum negative load that can be re-zeroed using the SAZSM (Low end of the SAZSM range)(Value determined in D). Re-zero the DUT using AZSM. The scale should indicate zero with a certain load on the plater.
- Start the flow of water so as to empty slowly the container "A" so that the AZSM will continuously rezero the weight of water being removed. Collect water in an empty container "B" that was previously tared. In this manner, continue emptying the container until the registration changes from zero (which will indicate that the negative limit of the AZSM range has been reached).
- When the indication changes to a value other than zero (thus signalling that the total AZSM Range has been exceeded), immediately stop the flow of water.
- The sum of the test weights removed and the weight of water collected in the container "B" represents the negative portion of the AZSM range.
- The sum of the positive and negative portion is the total range of SAZSM/AZSM. If the total value that can be zeroed exceed 4% of Max, proceed with Method 3: Zeroing to Capacity.
Method 3: Zeroing to Capacity
The purpose of this test is to determined if, by zeroing weight values in excess of 4%, the gross load that can be weighed is not increased beyond the device capacity limit.
- Remove all weights (Platter empty). Perform an initial zero setting (unplug and replug the device).
- Place test weights equal to 4% of Max on the LRE. Zero the device.
- Place an additional load (L1) (say 5% to 20% of Max) on the LRE. Zero that load. Load the device ("L2") until it gives an overload indication. Record the last weight value indicated ("I"). The scale must give an overload indication within the specified gross load limit (e.i. "I" equal to or less than Max - L1).
AA) If the scale limits the amount that can be zeroed at once with a SAZSM, but the operation can be repeated several times, zero the maximum possible load several times. The scale must give an overload indication within the specified gross load limit.
Interpretation of Results
If the total SAZSM and/or AZSM range(s) exceed 4% of the device capacity, the device is deemed to have complied with the requirement if the gross load that can be weighed is not increased beyond the capacity limit of the device.
Example: 15 kg x 0.005 kg computing scale
Step 1 0.600 kg (4%) placed on the scale; scale is zeroed. The scale indicates zero.
Step 2 An additional 5 kg is placed on the scale. The scale is zeroed.
Step 3 Load the scale until it indicates an overload condition. The maximum value that may be indicated is 10.045 kg (15 kg - 5 kg + 9d).
LG-15.04 IZSM Range (Maximum Range of Initial Zero Setting Mechanism)
Application:
This test is applicable to electronic indicators and to complete electronic devices.
Purpose:
The purpose of this test is to determine whether or not the total range of the initial zero setting mechanism exceeds 20%. The initial zero setting mechanism is the mechanism that sets the scale to zero upon power up.
Clarification
Electronic indicators tested and approved separately
The load receiving element to which an electronic indicator tested and approved separately will be interfaced will not have been tested up to 200% of Max. Consequently, the maximum Initial Zero Setting Mechanism range of electronic indicators must be limited to 20% of Max.
Test Procedure
Electronic indicators
Note: The following explanation of the test procedure is based upon the use of a load receiving element connected to the electronic indicator because it is easier to explain the procedure this way. However, the actual test can be performed using a loadcell simulator or a rheostat provided that the basic principles are maintained. The procedure consists of calibrating the electronic indicator so that it only uses a small portion of the total capacity of the LRE.
- Connect the indicator to a LRE and calibrate the indicator so that it is at a zero balance condition when the LRE is loaded at 50% of its maximum capacity and that it displays the number of intervals "n" (as requested by the applicant) when the LRE is fully loaded (Cap).
- By trial and error, find the -ve portion of the electronic indicator's IZSM range by removing a load(s) from the LRE and by trying to zero it using the electronic indicator's IZSM. The IZSM is triggered by unplugging and replugging the power cord (Note: on some devices, it is sufficient to switch it off and on).
- Similarly, by trial and error, find the +ve portion of the electronic indicator's IZSM range by adding a load(s) to the LRE and by trying to zero it using the electronic indicator's IZSM.
Complete electronic scale
Note: Whenever possible, perform the procedure described above for electronic indicators tested separately; or.
- Remove the platter in order to reach the lowest point of the IZSM range.
- By trial and error, find the +ve portion of the electronic indicator's IZSM range by adding a load(s) to the LRE and by trying to zero it using the electronic indicator's IZSM. The IZSM is triggered by unplugging and replugging the power cord (Note: on some devices, it is sufficient to switch it off and on).
Interpretation of Results
An electronic indicator tested and approved separately is deemed to comply with the requirements when the total range of the Initial Zero Setting Mechanism (absolute value of -ve portion of the range plus the +ve portion of the range) does not exceed 20% (or can be set to a maximum of 20% and sealed) of the DUT's maximum capacity (Max);
The IZSM range of a complete electronic device may exceed 20% of Max if the device performs within tolerances when the IZSM is set at the minimum and maximum points of its range.
When the IZSM range is limited to 20%, performance tests are conducted once: at the maximum IZSM setting. When the IZSM range exceeds 20%, certain performance tests are conducted twice: at the minimum and at the maximum setting of the range. See description of the performance tests in Part 3.
Reference: Section 31 of the Specifications.
Tare features must be designed and used to ensure accurate measurement and prevent the perpetration of fraud. There are numerous requirements that establish the proper operation of tare features depending upon the type of devices, the type of tare capability and the intended use of the device.
The extent of the requirements depends upon the application. For instance, design and operation requirements for devices used in direct sales to the public are more stringent than those applicable to devices used in other applications. In general, and unless otherwise specified for particular types of tare, devices must provide a clear indication for both the operator and the consumer that a tare value has been entered; platter and keyboard tare values must be visible at some point during the weighing process and the alteration of platter or keyboard tare values, during the weighing process, must be impossible without being noticed. On the other hand, devices that are used in industrial applications or in other applications where the consumer is not normally present need only provide the operator with a clear indication that a tare value has been entered and have a means to display the tare value on demand.
Definitions:
| Auto-tare | means an automatic platter tare. With the scale indication at zero, the scale automatically tares, within a pre-determined range, the value of the first load (container) put on the platter. The net weight of the commodity is then determined. |
| Keyboard tare | means a fixed or percentage tare value entered through the keyboard (e.g. 20g, 1.3%, etc.) or through one of the selectable tare keys to which tare values are assigned. |
| Percentage tare | means a tare value, expressed as a percentage (e.g. 5.6 %), that represents the percentage of tare material compared to the gross weight of the commodity. A percentage tare is one form of proportional tare. |
| Platter tare | means a tare entry achieved by placing an object (e.g. a container, bag, etc.) on the platter and pressing the tare key. The device then indicates zero as the net weight with the object on the platter. |
| Preprogrammed tare | means a tare value that has been entered, retained in the device memory and assigned to a PLU code or product name. It can be a fixed tare value and/or a proportional tare value. |
| Proportional tare | means a tare value, automatically calculated by the scale, proportional to the gross weight indicated by the scale. A proportional tare can be a percentage tare or a fixed tare value proportional to a range of gross weights (i.e., a 10 g tare for gross weights between 0 and 2 kg, a 20 g tare for gross weights between 2 and 4 kg, etc.). A proportional tare is, therefore, not limited to being a percentage tare. |
17.1 Applicable to any type of scale or weighing system and to any type of tare
17.1.1 The tare mechanism must only operate in the backward direction (under-registration). Perform the test described in LG-17.01.
17.1.2 The device must ignore or reject the entry of a zero tare value. The entry of a zero tare (or a 0% proportional tare) must not activate the "Tare Entered" or "Net" annunciator nor cause the display to automatically switch to the Net display mode. (Scales with a continuous tare display or tare display mode will indicate zero when the tare entry is zero. However, the entry of a zero tare must not cause the display to automatically switch to the net mode).
17.1.3 The tare value must be equal to the value of the displayed scale division for all methods of tare entry ( dtare = d). An attempt to enter a tare value that is not equal to "d" must be rejected or rounded off to the nearest scale interval (see section 22 for specific requirements pertaining to multi-interval and multiple range devices).
17.1.4 The tare weight signal must be "free floating". If the tare value is changed during the weighing operation, the net weight must be re-adjusted accordingly (Net + Tare = Gross).
17.1.5 The sum of the Tare value entered or preprogrammed and the Net weight that can be weighed must not exceed the Gross weight capability of the device (Max + 9 e for computing scales; Max + 5% for other scales). See overload test in section 14.
This does not preclude a device from having a full capacity tare plus a full capacity weighing range (additive tare). In such a case, tests for accuracy, repeatability, eccentricity, etc. must be performed based on the maximum weighing capacity with the maximum tare value entered.
17.1.6 It shall not be possible to enter a value of tare that exceeds the tare capability range (e.g., a tare entry of 6 kg on a scale with a tare range of 5 kg must be rejected and not taken as 5 kg).
17.1.7 Whenever Net, Gross and Tare weights are indicated or printed, they must be in exact mathematical agreement (Net + Tare = Gross) and the total price must be calculated on the basis of the net weight.
17.1.8 The use of any mechanism to select the unit of measure (lb/kg switch) must be inhibited when a tare is entered (through the keyboard, platter or preprogrammed) unless all weight values, including the tare value, are automatically converted and accurately rounded off to the nearest scale interval.
17.1.9 If a device is designed to automatically clear the tare after each weighing, it must also be designed to prevent the automatic clearing of a tare before a stable weight indication has been provided and the transaction completed.
Clarification:
On a price computing scale, the transaction is only completed with the entry of a unit price and the computation of the total price. The removal of the commodity from the platter before the total price is computed must not automatically cancel the tare.
17.2 Platter and keyboard tare
17.2.1 Pressing the tare button once, or several times, with a load on the platter (platter tare) must set the device to zero and only to zero.
17.2.2 Except for POS systems, the device must provide a visual confirmation or indication that a platter or keyboard tare has been entered (see the particular requirements for preprogrammed tares and POS systems).
Acceptable Means of Providing Visual Confirmation:
1. The device has a separate continuous display of tare.
2. The device displays simultaneously or in sequence (with a few seconds of interval), for both the operator and consumers, the Gross, Tare and Net weights with proper descriptors.
3. The device displays the net weight only, with an annunciator (Net legend) near the weight display. Gross weight is displayed when the tare weight entry is zero and the Net legend or annunciator is off.
4. A lighted legend or annunciator (Tare Entered) or similar statement is used to indicate that a tare value has been entered and the display indicates the net weight.
5. The device has selectable Gross and Net weight display modes with proper descriptors.
6. It is recommended that video display terminals that are the primary indicators of devices simultaneously display the Gross and Tare weights when the Net weight value has been determined.
Note: Annunciators or descriptors must go "on" when tares are entered; not "off".
17.2.3 The entry of a platter or keyboard tare must automatically override any previous tare entry or be rejected (i.e., they cannot be additive). A percentage tare value may however be entered in addition to a fixed keyboard or platter tare value.
17.2.4 Unless a separate tare display is provided, the device must display a negative weight value when the weight of the load on the platter is smaller than the tare weight.
17.3 Preprogrammed tare (fixed or percentage)
17.3.1 Preprogrammed tare values may only be assigned (programmed) when the device is at gross load zero and in a "configuration" mode.
17.3.2 Fixed and/or percentage tares may be preprogrammed into PLU codes. PLU codes may be entered or changed at any time, whether or not a load is on the platter.
17.3.3 Except for POS systems, scales must display the Net weight ("net" legend on) when a preprogrammed tare is entered through a PLU code.
17.4 Percentage tare
17.4.1 Fixed and percentage tares may be added to obtain a total tare value for a transaction. For instance, a PLU code may be preprogrammed with cumulative fixed and percentage tares; or a fixed platter or keyboard tare may be entered first, and then, through a PLU code, a percentage tare applied.
17.4.2 If a device can sum fixed and percentage tare values, the two values must be added first and then the total tare value rounded off to the nearest scale interval. There is therefore no benefit in expressing percentage tare values with more than one decimal place (e.g. 1.5 %, 3.3 %, etc.).
Examples:
| Scale | Total gross weight TGW | Fixed tare weight FTW | Gross weight GW = TGW-FTW | Percentage tare value %T | Percentage tare weight calculated GW x %T | Total gross weight (TGW) | Total tare (fixed + percentage) | Net weight NW | |
| Calculated | Rounded | ||||||||
| 15 kg x 5 g | 355 g | 10 g | 345 g | 9.2 % | 31.74 g | 355 g | 41.74 g | 40 g | 315 g |
| Multi-interval 0-2 kg x 1 g 2-5 kg x 5 g | 2890 g | 9 g | 2881 g | 11.2% | 322.672 g | 2890 g | 331.672 g | 330 g1 | 2560 g |
| 332 g2 | 2558 g3 | ||||||||
1 Tare rounded to the nearest 5 g scale interval (interval for weighing range of the gross weight).
2 Tare rounded to the nearest 2 g scale interval (interval for weighing range of the tare weight).
3 See sections 22.1.7 and 22.1.10 for specific requirements applicable to multi-interval and multiple range devices.
17.4.3 The visual confirmation that a tare has been applied (i.e., "Net" annunciator) must only be enabled if the percentage tare multiplied by the gross weight represents one or more scale intervals after the appropriate rounding. The turning on of the "Net" annunciator must only occur if the net weight does not equal the gross weight (i.e., a tare has actually been applied to the gross weight).
| Note: | The percentage tare of a commodity is determined as follows: | ||
| Percentage tare (%T) = | Tare weight | x 100 % | |
| Gross weight | |||
| Net weight (NW) is determined as follows: | |||
| NW = TGW - FTW - [(%T)(TGW-FTW)] | |||
17.5 Devices used for direct sale to the public
17.5.1 Except for preprogrammed tare, proportional tare and POS systems, when keyboard or platter tare values are entered the scale must comply with one of the following requirements:
17.5.1.1 the tare value is permanently indicated on a separate dedicated display; or
17.5.1.2 the tare value is indicated as a negative value when there is no load on the load receiving element;
17.5.2 A platter or keyboard tare value may not be entered, modified or cancelled unless the device is at gross load zero or the device indicates a negative weight value. This does not apply when the tare is continuously indicated on a separate dedicated display (or, as a minimum, the new tare value is clearly displayed to the customer at some point during the transaction) nor to a preprogrammed tare associated with a PLU.
Example:
A platter or keyboard tare value is entered on a computing scale and a negative value is indicated. If the wrong tare value was entered, it may be cancelled and replaced by a new tare value when the platter is empty. This new tare value will be indicated as a negative weight value. However, the correction must not be possible with a commodity resting on the platter (positive weight indication). In such instances, the operator must remove the commodity from the platter and then cancel or change the tare value.
Clarification:
The zero indication/no load condition does not apply to a preprogrammed tare value. The idea being that the operator should not be capable of altering a tare value without providing the consumer with an indication that a new tare value has been entered. In the case of a preprogrammed tare associated with a PLU code, the tare value is rarely displayed. However, it is unlikely that the operator will select the wrong PLU code or product name, or change the PLU code during the weighing operation, to reduce the tare value. Such actions would affect the unit price and would be detectable by the consumer.
17.5.3 Platter or keyboard tare values may be retained between transactions.
17.5.4 Auto-tares are prohibited in direct sale to the public applications.
17.6 Devices intended for industrial applications or other applications where consumers are not normally present
17.6.1 A tare may be cancelled or modified while a load is on the load receiving element provided that the device has means to indicate, on demand, the value of the tare. These means include a negative weight value displayed when the platter is empty or a means to recall the tare value. A clear indication must be provided to the operator that a tare has been entered or cancelled (a tare annunciator is sufficient).
17.6.2 Tare values may be retained between transactions.
17.6.3 Combined semi-automatic zero/tare buttons are permitted under the following conditions:
17.6.3.1 The requirements of section 15.2 for semi automatic zero setting mechanisms must be met. Namely the zero/tare mechanism operates only when the scale provides a stable indication; the mechanism sets the indication to zero, only, within ± 1/4 e (or ½ d for Class I and II devices equipped with auxiliary reading means); the zero range does not exceed 4% of scale capacity unless the gross load that can be weighed is not increased beyond scale capacity.
17.6.3.2 The scale is intended to be used exclusively for industrial applications or applications where consumers are not normally present.
17.6.3.3 The AZSM or Center-of-Zero annunciator must be effective when the device displays zero after a zero setting operation (within the zero range). The AZSM may also work when zero is indicated after a tare operation. See section 10.3.
17.6.3.4 The AZSM operates as prescribed in section 15.3. Namely, the AZSM does not re-zero weight values in excess of 0.6 e; the total AZSM range does not exceed 4% of scale capacity unless the gross load that can be weighed is not increased beyond scale capacity.
17.6.3.5 The scale must be permanently marked, near the weight display(s), with the legend "Not for Use in Direct Sale to the Public" or similar language and the ranges of both zero and tare operation (e.g. Zero Range up to 7 d - Tare Range above 7 d).
17.6.3.6 The range of zero and tare operation must not be user selectable (i.e. fixed or, as a minimum, a sealable parameter).
17.6.3.7 Visibility of operation - the scale is required to display an indication ("Net" annunciator) that a tare has been entered when a weight value within the tare range is subtracted by activating the zero/tare button.
17.7 Point of sale systems
Definition:
a weighing element or a non computing scale interfaced with an electronic cash register or computer. Usually, the cash register or computer reads the gross weight provided by the scale, assigns a tare through a PLU code and prints a net weight on the cash register tape. The cash register must not interfere with the operation of the scale. A stand alone price computing scale used in conjunction with an electronic cash register would not fall into this category.
17.7.1 A POS system may display the Gross weight on the scale display; however, it must print the Net weight on the cash register tape. The scale of a POS system is not required to display the net weight nor provide an indication that a tare value has been entered.
17.8 Multi-interval and multiple range scales
See section 22.0 of this manual.
17.9 Customers' scoreboard
See section 23.0 of this manual.
LG-17.01 Tare - Backward direction
Purpose
The following test is to ensure that a weight value (positive tare) cannot be added to the weight of a load being weighed.
Application
Applicable to complete electronic scales and electronic indicators equipped with a tare function.
Test Procedure:
Push button tare
- Zero the DUT
- Place a weight in excess of the AZSM range on the load receiving element, and re-zero the scale
- Activate the tare mechanism (Push Button Tare), the scale should indicate zero.
- Remove the weight; this should result in a negative indication
- Attempt to take this value as tare using the push-button tare capability. The negative number should not be taken as a tare.
Key-Board Tare, Programmable Tare
A. Attempt to enter or pre-program a positive tare through the Key-board.
Interpretation of Results
The DUT is deemed to comply with the requirement, if a "positive" value cannot be entered or programmed as a tare value.
Reference: Section 30 , 31, 32 and 45 of the Specifications
Electronic devices must have motion detection capability to prevent the device from zeroing (semi-automatic zero) or taring (platter tare) a part of the load when the semi-automatic zero or tare key is activated while a load is added, changed or removed from the platter.
Electronic devices equipped with a printer (or that have connection for a printer) must have motion detection capability to prevent the device from printing values before the weight display has stabilized. This reduces the possibility of recording incorrect weight values.
The following test procedure is used to asses the effectiveness of the motion detection feature.
LG-18.01 Motion Detection Test
Application:
Applicable to complete electronic scales, or to electronic indicators which are intended to be used as part of a non-automatic weighing electronic scale (tested by means of a load cell\dead load tester assembly or by means of a load cell simulator).
Purpose:
To determine if printing, zeroing or the entry of a tare is inhibited when motion is detected.To evaluate the maximum range within which printing is possible in spite of motion.
Test Sequence:
- Place a load within the weighing range on the platter and allow time for the indication to stabilize.
- Induce a motion to the scale indications to a peak magnitude of at least 10 e (amplitude);
- While disturbing the weight indication, activate the SAZSM and allow the oscillations to settle out. The scale may eventually zero the load or may reject the command.
- While disturbing the load, attempt to activate the tare button (platter tare). The scale may eventually tare the load on the platter, or reject the command.
- While disturbing the load, attempt to print. The scale may print a weight or reject the command.
- Repeat the test at least five times for small loads ( near zero) and loads near capacity
Note:
For larger capacity devices, it may not be convenient or practical to disturb the load by hand. A load of greater than 10 e may be applied or removed while activating the zero, tare, stored weight or print key.
Under laboratory conditions, since this is primarily an instrument test, a low capacity load cell or a load cell simulator may be connected to the device or the indicating element to simulate motion.
Interpretation of Results:
The device complies with the requirements if zeroing, taring or printing the load on the platter is prevented, or is within 1 verification scale interval (e) for scales that have a maximum capacity of 2000 kg (5000 lb); or 3 verification scale intervals (e) for scale of more than 2000 kg (5000 lb), and if the printed weight is within the prescribed tolerances.
18.1 Push-button zero complies with the motion detection requirements
18.2 Push-button (platter) tare complies with motion detection requirements.
18.3 Stored weight key(s) comply with the motion detection requirements.
18.4 Printed weight values comply with motion detection requirements.
18.5 Printed values are within prescribed tolerances.
19.0 Tilting (Off-Level Effect)
Reference: Section 21 of the Specifications
Under section 21 of the Specifications, portable or movable devices, other than of the freely suspended type, must perform within tolerances when tilted up to 3°, in any direction. If they can perform within tolerances only when levelled, they must be equipped with permanent and sensitive level indicating means (usually a bubble level).
Vehicle mounted weighing devices such as onboard weighing systems for NH3, onboard weighing systems for waste collection, and scales mounted on lift trucks must be able to provide an accurate weight reading up to at least 3°.
19.1 Portable or movable devices
Complete scales or load receiving elements other than onboard weighing devices must meet one of the following conditions:
19.1.1 The device weighs within prescribed tolerances, when off level by up to 3° or
19.1.2 The device is equipped with a permanently installed level indicator as standard feature.
If the device is not equipped with a suitable level indicator, perform the tests described in LG-3.04 of Part III, Performance Tests.
If the device has a level indicating means, the following requirements must be met:
19.1.2.1 The level indicating means must be permanently and rigidly mounted on a permanent section of the scale. It must be located so as to be easily read. It must be protected from damage and must be sufficiently sensitive.
19.1.2.2 The level indicating means must be readily observable without disassembly that requires the use of tools.
Clarifications:
- On small portable devices, the level indicating means may be placed under the platter (if the platter can be lifted easily) or at the back of the scale (if it can be readily observed).
- A bubble level placed under the platform of a movable floor scale is not acceptable if the platform is relatively heavy and requires tools or assistance to be lift up in order to access the level indicator.
- The level indicating means must be permanently attached to a permanent part of the scale (e.g. it is not sufficient to attached it to the platter if the patter is removable).
19.1.2.3 The level indicating means must be sufficiently sensitive. Perform the test described in LG3.05, Part III , Performance Tests.
19.2 Onboard weighing systems
Definitions: a weighing device designed as an integral part of or attached to or secured to the frame, chassis, lifting mechanism or the bed of a mobile equipment such as a vehicle, trailer, tractor, or forklift.
19.2.1 The device provide a weight indication up to 3° in any upright direction.
19.2.2 The device weighs within tolerances when off level by the largest of
a) 3° or
b) the maximum inclination at which a weight indication is still provided.
19.2.3 The weight indication blanks when the inclination is such that the device ceases to weigh accurately.
19.2.4 Scales mounted on lift trucks (or similar vehicles) must blank their indications when the lift truck is moving, unless the scale can provide an accurate weight indication. Perform an accuracy (in-motion) test using different loads within the capacity range of the device. The test must simulate actual conditions of use.
Note: See the complete test procedure LG-3.04, Part 3, Performance Tests.
It is recommended that electronic devices incorporate a test system for verifying all relevant signs of the indicator in their active and non-active state sufficiently long to be checked by the operator.
Clarification:
1. The relevant signs of an indicator are those that are metrologically significant: digits for gross, net and tare weights; + or - signs; tare or Net annunciator; centre of zero light; etc..
2. The following means of verifying signs are acceptable:
- Test sequence initiated by pressing a special button
- Test sequence initiated by pressing key or a sequence of keys
- Test sequence initiated by turning the scale off and on
This is Not a Requirement
21.0 Multiple Deck Weighing Systems
Reference: Sections 30 to 33 of the Specifications
An indicator and/or printer may be connected to more than one weighing element provided that the weighing system is designed to ensure accuracy of the transactions, and to prevent erroneous measurements or fraud.
Two basic Multiple Deck Weighing Systems are used in trade:
- a system where only one weighing element can be selected and use at a time; and
- a system where all the weighing elements can operate simultaneously. Each weighing element may have its own indicating element; all indicating elements being connected to a summing weight indicator. Or the weighing elements are connected to a specially designed multi-deck indicating element that can display simultaneous or alternating weight values from the individual weighing elements, and can display the sum of the weights. This second type of Multiple Deck Weighing system is normally used to weigh vehicles.
21.1 Systems where only one weighing element can be selected and use at a time (Multiplex).
Each separate weighing element and the indicating element is considered a separate scale and must be tested accordingly. In addition to other applicable requirements:
21.1.1 The system or scale must prohibit the use of any weighing element that is not in use (only one weighing element at a time).
21.1.2 The indicating element must automatically provide a clear and continuous indication of which load-receiving element is in use (i.e. Scale A, Scale B, Scale C; Scale 1, Scale 2, etc..). The indication must be visible from the operator's normal position.
21.1.3 Weighing elements must be clearly and permanently identified with the corresponding identification.
21.1.4 The printer must provide on the ticket, for each weighing, a clear registration indicating which weighing element was used (Scale A, Scale B , etc..).
21.1.5 When an operator-activated function (Setting zero, entering a tare value, selecting or clearing a function, etc..) is performed on one particular weighing element, functions or parameters of other weighing elements must not be affected or altered. Perform the test described in LG-21.01
21.1.6 Unless the indicator has independent AZSMs, one for each individual weighing element, individual Centre-of-Zero indicators (annunciators), one for each weighing element, must be provided. Centre-of-Zero indicators must provide a continuous signal (remain active) regardless of which weighing element is selected.
It is preferable to identify scale weighing elements as scale A, scale B, etc. rather than scale 1, scale 2. Numbers that could be confused with weight indications is not acceptable.
21.2 Systems where all the weighing elements can operate simultaneously (Vehicle scales, vehicle axle weighing scales); each weighing element has its own dedicated display that are interfaced to a summing display.
21.2.1.1 each weight indicator must be clearly and permanently identified (i.e. Scale 1, Scale 2, Total weight, etc..). Each weight display and its associated weighing element is considered a separate scale and must meet all applicable requirements.
21.2.1.2 When an operator-activated function (Setting zero, entering a tare value, selecting or clearing a function, etc..) is performed on one particular weighing element, functions or parameters of other weighing elements must not be affected. Perform the test described in LG-21.01.
21.2.1.3 Unless the indicator has independent AZSMs, one for each individual weighing element, individual Centre-of-Zero indicators (annunciator), one for each weighing element, must be provided. Centre-of-Zero indicators must provide a continuous signal (remain active) regardless of which weighing element is selected.
21.2.2.4 Weighing elements must be clearly and permanently identified with the corresponding identification (Scale A, Scale B, etc..).
21.1.2.5 The printer must automatically register the printed weight associated with the weighing element identification that was used (Scale A, scale B, etc)
21.2.1.6 The value of verification scale interval must be the same for all displays including the summing display.
21.2.1.7 The summing weight display must perform within tolerances; must not indicate nor record any weight values when one individual weighing element exceeds its capacity; must sum any tare entries in the individual indicators; must have a free floating weight signal for summing individual indicators; and must be in mathematical agreement with the sum of all the individual indicators.
LG-21.01 Alteration of settings or data entries
Purpose
The purpose of this test is to ensure that when a setting is performed or a function is activated on one particular weighing element, functions or settings of the other weighing elements are not changed or altered.
Application
Applicable to any Multiple Deck Weighing Systems or indicator intended for Multiple Deck Weighing Systems
Test Procedure
- Zero each individual weighing element
- Place a small load (say 5 e) on one of the load weighing element; zero that weighing element; verify if zero balance condition of the other weighing elements have changed;
- Enter a platter or key board tare for each selection of weighing elements in each weighing; clear or change the tare value on one weighing element; verify if tare values of the weighing elements have been altered.
- Place different combination of loads on the weighing elements; ensure that the weight are correctly and accurately indicated; ensure that the printed weights agree with indicated weights and are properly identified.
- If applicable, ensure that the summing weight display perform within tolerances; does not indicate nor record any weight values when one individual weighing element exceeds its capacity; sums any tare entries in the individual indicators; has a free floating weight signal for summing individual indicators; and is in mathematical agreement with the sum of all the individual weight displays.
Interpretation of Results
The device complies with the requirements if functions performed on individual weighing element does not affect the settings or entries of other weighing elements; if the indicated and printed weights are accurate and identified as required; and if the summing weight display meets the requirements of E above.
22.0 Multi-Interval Devices and Multiple Range Devices
Reference: Sections 3, 5, 6, 8, 9, 16, 31 to 33 of the Specifications
This section provides additional guidelines for the examination and testing of multi-interval and multiple range devices.
Note: a weight indicator tested separately will be set and tested for a maximum number of intervals ( nmax ) and for a minimum value of verification scale interval ( emin ) across the range.
22.1Multi-interval devices
Multi-interval device means a device having one weighing range which is divided into partial weighing ranges each with different scale intervals, with the weighing range determined automatically according to the load applied (pre-determined ranges/intervals), both on increasing and decreasing loads.
Intervals and capacities
22.1.1 On a multi-interval device, the value of the verification scale interval of a particular range must be lower than the value of the verification scale interval of the next range ( e1 < e2 < e3, etc.)
22.1.2 Each partial range of a multi-interval device must have the same value of scale interval for both increasing and decreasing loads. The verification scale interval e must equal the scale interval d.
22.1.3 Each partial range of a multi-interval device must have the number of scale intervals (n) required by section 3 of the Specifications.
Example: each range of a Class III device must have a minimum of 500 n and a maximum of 10 000 n. The number of scale intervals "n" for each weighing range is determined by dividing the scale capacity for each range by the verification scale interval "e" for each range. See the following illustration:
| Partial Weighing Range (Capacity) | e | n | Max/e |
| 0-3 kg | 1 g | 3000 | 3000/1 |
| 3-6kg | 2g | 3000 | 6000/2 |
| 6-15kg | 5g | 3000 | 15000/5 |
Example of a device that would not satisfy the above section 22.1.3
| Weighing Ranges | e | n |
| First-1kg | 1g | 1000 |
Second 1-5kg |
5g | 1000 |
| Thrid 5-8kg | 20g | 400 |
Example of a device that satisfies section 22.1.3
| Weighing Ranges | e | n |
| First-1kg | 1g | 1000 |
| Second 1-5kg | 5g | 1250 |
| Thrid 5-8kg | 20g | 1600 |
22.1.4 It is recommended (OIML requirements) that the maximum capacity of a partial weighing range of a multi-interval device (except the last range) must satisfy the requirements of the following table:
| Class | I | II | IIII | IIII |
| Maxi/ei+1 | ≥ 50 000 | ≥ 5 000 | ≥ 500 | ≥ 50 |
Tare features
22.1.5 The maximum tare value that may be entered shall not exceed Max 1.
22.1.6 Whenever gross and tare weights fall in different weighing ranges, the net weight must always be in mathematical agreement with the gross and tare weights that are displayed and recorded (simultaneously or in sequence) (gross = tare + net).
22.1.7 The tare value must be equal to the value of the displayed scale division for all methods of tare entry (dtare = d). An attempt to enter, in the first range of a multi-interval scale, a tare value that is not equal to d must be rejected or rounded off to the nearest scale interval. Example: a multi-interval scale has a 2 g interval in the first range and 5 g in the second range. A keyboard entry of 5 g in the first range must be either rounded to 4 or 6 g or rejected.
22.1.8 Weight values (Net or Gross) must always begin with the lowest weighing range on the device regardless of the amount of keyboard or platter tare that is taken. Example: a multi-interval scale has two ranges: first 0-2 kg by 2 g, and second 2-5 kg by 5 g. A platter tare of 1 kg is taken; the device indicates zero. Then, the device must indicate the net weight from 0 up to 2 kg in intervals of 2 g; and from 2 up to 4 kg, in intervals of 5 g.
22.1.9 When Gross, Tare and Net weights are indicated or printed, there shall be mathematical agreement in all circumstances. The tare value must be rounded off to permit mathematical agreement. Example: A multi-interval device has two ranges . The first range 0-2 kg by 2 g, and the second 2-5 by 5 g. A key board tare of 1.998 kg is entered (in 2 g divisions); a gross load of 2.115 (in 5 g divisions) is put on the platter. The net weight indicated must be either 0.116 kg or 0.118 kg (first range; rounded off to 2 g division). If the gross, net and tare weights are indicated, they must be as follows:
| Gross | Tare | Net | |
| either | 2.115kg | 1.999kg | 0.116kg |
| or | 2.115kg | 1.997kg | 0.118kg |
22.1.10 A tare value entered in the lower range may be either rounded off to the nearest value of the interval of the higher range in which the weighing occurs, or kept unchanged. In the latter case, the net weight could possibly be displayed with an interval smaller than the interval of the range in which the weighing occurs. When a device displays or prints the gross, net and tare values, in all cases the mathematical equation "tare + net weight = gross weight" must be satisfied. Example: a multi-interval scale has a 2 g interval from 0 to 2 kg, and 5 g from 2 kg to 10 kg. A tare of 12 g is entered in the first range and the gross weight is 2500 g (second range). The scale may display either 2488 g (tare stored as 12 g) or 2490 g (rounded off to 10 g).
Note:
OIML: tare must be rounded off (R 76-1, section 4.7.1)
U.S.: tare must be either rounded up or kept unchanged (Pub 14 page 1-44)
The rounding off of the tare value is the method prefered by Measurement Canada. MC may allow only this method sometime in the future.
Marking
22.1.11 The capacity and verification scale interval must be conspicuously marked near the weight display (See section 1.1.6, 1.1.7 and 1.1.8 of this manual).
Performance
Clarification:
- For any test performed on a multi-interval scale, the tolerance is a function of the verification scale interval e of the range corresponding to the test load used.
- The smallest value of the verification scale interval applies to the tests to determine the maximum value of AZSM, the maximum permissible error for the return to zero test and for the creep-return to zero test, etc. The motion detection requirement must be satisfied for each partial range. The shift test must be performed at one-half of the capacity of each partial weighing range.
- temperature effect on no load: the tolerance ( one verification scale interval/ 5°C) applies to the smallest verification scale interval.
- time (half hour creep/return to zero): The deviation on returning to zero as soon the indication has stabilized, after the removal of any load which has remained on the device for half hour, shall not exceed 0.5°e1.
- Devices equipped with keyboard or platter tare must meet the tolerances for net loads for any tare taken up to the maximum tare capacity.
22.2 Multiple range devices
Multiple range device means a device having two or more weighing ranges with different maximum capacities and different scale intervals for the same load receptor, each range extending from zero to its maximum capacity (two or more devices in one). The selection of the range may be manual or automatic.
Number of intervals and capacity
22.2.1 Each range of a multiple range device must have the number of scale intervals (n) as required by section 3 of the Specifications.
22.2.2 For each range, e must equal d.
Zero setting feature
22.2.3 The zero setting feature in any weighing range must also be effective in the greater weighing ranges, if switching to a greater weighing range is possible while the device is loaded. The deviation from zero must be no more than 0.25 e. This is applicable to manual selection or automatic changing of weighing ranges.
Selection of the weighing range
22.2.4 i) Manual selection of the weighing ranges is allowed from a smaller to a greater weighing range at any load;
ii) It is allowed from a greater to a smaller weighing range when there is no load on the platter, and the indication is zero or at a negative net value. The tare operation must be cancelled and zero must be set to ± 0.25 e1, both automatically.
22.2.5 i) Automatic changeover of the weighing range is allowed from a smaller to the following greater weighing range when the load exceeds the maximum gross weight of the range being operated;
ii) It is allowed from a greater to a smaller weighing range when there is no load on the platter and the indication is zero or at a negative net value; the tare operation must be cancelled and zero must be set to ± 0.25 e1, both automatically.
Tare features
22.2.6 The tare value may only be transfered from one weighing range to another one with a larger verification scale interval.
22.2.7 The tare operation shall be effective also in the greater weighing range, if switching to a greater weighing range is possible when the device is loaded.
22.2.8 The tare value must be equal to the value of the displayed scale division for all methods of tare entry ( dtare = d). An attempt to enter, in the lower range of a multiple range scale, a tare value that is not equal to d must be rejected or rounded off to the nearest scale interval. Example: a scale has a 2 g interval in the first range and 5 g in the second range. A keyboard entry of 5 g in the first range must be either rounded to 4 or 6 g or rejected.
22.2.9 A tare value entered in the lower range must be rounded off to the nearest interval of the higher range in which the Net weighing occurs. Example: an automatic multiple range scale has a 2 g interval from 0 to 2 kg (lower range), and 5 g from 0 kg to 10 kg (higher range). A tare of 13 g is entered in the lower range and the gross weight is 2500 g (second range). The tare value must be rounded to 15 g and the scale must display 2485 g (rounded off to 15 g).
Note:
OIML: tare transfered only from the lowest to the largest range and rounded off to the scale interval (R 76-1, section 4.7.1).
U.S.: tare transfer only from the lowest to the largest range and must be rounded up (Publication 14, page 1-46)
22.2.10 In all cases, the mathematical equation Tare + Net must = Gross (indicated and printed).
Indication of the range in use
22.2.11 The range in which the device operates shall automatically and clearly be indicated for both the operator and the consumers.
Clarification:
If a scale has a decimal point and a different number of decimal places in each weighing range, the position of the decimal point and the number of digits following is an adequate definition of the weighing range in use. If the weighing range does not utilize a decimal point and differing numbers of decimal places (e.g. scale division are 20, 50 and 100 lb), another method must be provided to indicate the weighing range in use. A display of the capacity by division with an annunciator located near the weight display such as the following is acceptable:
Range in use
| Range 1 | 20 x 0.005 kg | • |
| Range 2 | 5 x 0.002 kg | º |
Marking
22.2.12 Each weighing capacity by division must be clearly indicated near the weight display. If the manufacturer chooses to indicate which weighing range is in operation using the method recommended above (with annunciator), no other marking of capacity by division is required.
Performance
Clarification:
- Each weighing range of a multiple range scale is considered to be an individual scale and must be evaluated accordingly.
- temperature effect on no load the tolerance ( one verification scale interval/ 5EC) applies to the smallest verification scale interval.
- time (half hour creep/return to zero) The deviation on returning to zero from Max1 shall not exceed 0.5 e1. The deviation on returning to zero from Maxi shall not exceed 0.5 ei.
Furthermore, after returning to zero from any load greater than Max1, and immediately after switching to the lowest weighing range (manually or automatically), the indication near zero must not vary by more than e1 during the following 5 minutes.
23.0 Devices Used for Direct Sale to the Public
Reference: Sections 30 to 33, 46, 47, 50, 59 and 60 of the Specifications
Several requirements apply to devices intended to be used for direct sale to the public. These requirements are to ensure that transactions are accurate and that customers normally present during the weighing operations are provided with sufficient information so that they can observe and understand the weighing process.
23.1.1 The device must be provided with a display (customer display) that duplicates all significant metrological information displayed for the operator (Weight, unit price, total price, tare weight, annunciators for "net" weight or "tare entered", centre-off-zero light, etc.); or, as a minimum, the scale must have a connection for a separate duplicate display (Customer display must be submitted to the Laboratory for evaluation).
23.1.2 Customers' scoreboard Scoreboards on vehicle scales, livestock scales, etc. do not require approval. However they must have the following features:
- the weight indication must be free floating;
- they must either indicate a negative sign or blank when the weight indication on the scale is behind zero;
- they must blank when the weight indication exceeds the scale capacity ( Max + 105%);
- they must indicate the unit of measurement. Note that a sign adjacent to the weight indication is sufficient when there is only one unit of measurement; if there is a lb/kg switch on the primary indicator, the scoreboard must indicate the unit in use;
- they must be able to indicate zero;
- they must indicate the weighing mode (gross, net, tare)
- Max, d and e, if different than d must be marqued near the weight display
23.2 (Reminder) See item 7.3, Section 7.0 in this manual:23.2.1 The devices must display the unit price if the total price is displayed;
23.2.2 if the device displays in kilograms, the unit price that can be entered and displayed is limited to Price/100 g and Price/kg; if the device displays in Canadian units, the unit price that can be entered and displayed is limited to Price/pound; if the device displays weight values on the basis of the gram or ounce, unit prices may also be entered and displayed on that basis.
23.3 (Reminder) See item 17.4, Section 17.0 in this manual:
23.3.1 Except for pre-programmed tare, proportional tares and POS systems, when keyboard or platter tare values are entered, the scale must comply with one of the following requirement:
23.3.1.1 the tare value is permanently indicated on a separate display; or
23.3.1.2 the tare value is indicated as a negative value when there is no load on the load receptor.
23.3.2 A platter or keyboard tare value may not be entered, modified or cancelled unless the device is at gross load zero or the device indicates a negative weight value. This does not apply when the tare is continuously indicated on a separate display and to pre-programmed tare.
23.3.3 Platter or keyboard tares may retained between transactions.
Example:
A platter or keyboard tare value is entered in a computing scale; a negative value is indicated. If the wrong tare value was entered, it may be cancelled and replaced by a new tare value when the platter is empty. This new tare value will be indicated as a negative weight value. However, the correction must not be possible with the commodity resting on the platter (positive weight indication). The operator must remove the commodity from the receptor and then cancel or change the tare value.
Clarification:
The zero indication/no load condition does not apply to a preprogrammed tare value. The idea is that the operator should not be capable of altering a tare value without providing the consumer with an indication that a new tare value was entered. In the case of a pre-programmed tare associated with a PLU code, the tare value is rarely displayed. However, it is unlikely that the operator will select the wrong PLU code or product name, or change the PLU code during the weighing operation to reduce the tare value. It would affect the unit price which would be detectable by the consumer.
23.3.4 Auto-tares are prohibited in direct sale to the public applications.
Note: Devices that are not intended for direct sale to the public but resemble those approved for direct sale to the public, must be marked as follows: << Not for Use in Direct Sale to the Public>> or words that convey the same meaning. The marking must be permanent and located near the weight display so that it is readily observable by the user.
24.0 Weigh-in/Weigh-out Systems
Reference: Sections 30 to 33 of the Specifications
A weigh-in/weigh-out system is typically a vehicle scale in which an inbound truck is weighed either loaded or empty, the inbound weight is stored, the truck is then emptied or loaded as the case may be, the outbound truck is weighed and the larger of the two weights (outbound or stored weight) is printed as the gross weight, the other printed as the tare weight and the difference computed as the net weight. Inbound weights, recalled weight values, and gross, tare and net weights must be identified to clearly document the transaction. The storage, recalling, and printing actions are limited so that they do not facilitate fraud. The followings are the main requirements for inbound/outbound weighing systems.
24.1 Any inbound weight values must be recorded and automatically identified as such (assigned to a client name or number). If inbound weights are not printed at the time the weigh-in operation is performed, the inbound weight information must not be lost during a power interruption.
24.2 The gross, tare and net weight values must be recorded (printed) in an automatic sequence when the outbound weight value is obtained.
24.3 The recorded weight value is not required to be automatically identified as a gross weight value, provided that the other two weight values are clearly and automatically identified as net and tare.
24.4 If a device can indicate and/or record in two and more weight units, all gross, tare and net weight values shall be automatically recorded in the same weight units. This condition must be met regardless which weight unit is being displayed.
24.5 Any weigh-in/weigh-out weight values stored in the memory register shall automatically clear and not be retained in memory after a complete transaction of gross, tare and net has been recorded.
24.6 Any recorded weighing value from the memory register shall be automatically identified and defined (client name or number).
24.7 Tare values shall not be stored as negative values. (Negative numbers shall not be accepted).
24.8 Keyboard tare entries shall not be accepted into weigh-in/weigh-out memory registers.
24.9 If the system is equipped with a tare memory register for weighing gross, tare and net separate from the weigh-in/weigh-out feature, the tare weight shall not interact with the weigh-in/weigh-out feature.
24.10 The data processing system performing the weigh-in/weigh out operation shall only accept weight values when the scale indicator is in the gross mode, or give an error signal.
25.0 Non Metrological Functions
Reference: Sections 32 and 33 of the Specifications
A device may perform functions, other than metrological, such as accounting functions provided that those non metrological functions do not alter the device metrological characteristics or functions, and neither lead to measurement errors nor facilitate the perpetration of fraud.
25.1 Non metrological functions do not alter the device metrological characteristics or functions, and neither lead to measurement errors nor facilitate the perpetration of fraud.
Appendix 2-A
The following table lists acceptable defining words and symbols for the marking of devices. This list does not standardize the abbreviation or symbols that must be used, rather it identifies abbreviations or symbols routinely used. Other abbreviations or symbols, such as those internationally recognized (OIML), are also acceptable.
Corrected May 10, 1999
Abbreviations and symbols accepted in Canada |
|||
Units |
Definition |
Acceptable symbol |
Not |
kilogram |
basic unit |
kg |
KG, kilo |
gram |
1/1 000 kg |
g |
gr, gm, G, GM |
pound |
0.45359237 kg |
lb |
LB, lbs, # |
ounce |
1/16 pound |
oz |
OZ |
dram |
1/16 ounce |
dr |
DR |
grain |
1/7 000 pound |
gr |
GRN, grn, GN, g |
tonne (or metric ton) |
1 000 kg |
t |
T, TN, tn |
ton |
2 000 pounds |
tn |
t, TN, T |
cental (or hundredweight) |
100 pounds |
ctl or cwt |
|
troy ounce |
480 grains |
tr oz |
|
carat |
200 milligrams |
ct |
c |
|
Zero key or center of zero indicator |
|
|
Tare entered |
|
||
Accuracy class
|
Class I, II, III, I or II |
I, II, III, III HD, IV |
|
|
Maximum number of scale intervals |
nmax |
|
|
Minimum verification scale interval |
emin |
|
|
Value of the actual scale interval |
d |
|
|
Value of the verification scale interval |
e |
|
|
Number of scale intervals |
n |
|
|
Gross weight |
gross, G, GR |
|
|
Tare |
tare, T, TA |
|
|
Net weight |
net, N, NT |
|
|
Manual weight entry |
manual weight |
M, MW, MAN |
Additional authorized symbols
Corrected May 10, 1999
Units |
Symbols |
Units |
Symbols |
Acre |
no symbol allowed |
Inch (pouce) |
in (po) |
Bushel (boisseau) |
bu |
Link (chaînon) |
li (chon) |
Chain (chaîne) |
ch |
Mile (mille) |
mi |
Dram (drachme) |
dr |
Peck (quart de boisseau) |
pk |
Fluid dram (drachme fluide) |
fl dr |
Pint (chopine) |
pt (chop) |
Fluid ounce (once fluide) |
fl oz |
Quart (pinte) |
qt (pte) |
Foot (Pied) |
ft (pi) |
Rod, perch, pole (perche) |
no symbol allowed |
Furlong |
no symbol allowed |
Ton (tonne) |
tn |
Gallon |
gal |
Yard (verge) |
yd (vg) |
Gill (roquille) |
gi |
|
|
Appendix 2-B Draft Specifications for Metrological Audit Trails (May 1996)
Title
Specifications Relating to the Design, Composition, Performance and Use of Metrological Audit Trails.
1.0 Application
1.1 These Specifications apply to audit trails incorporated in weighing and measuring devices and systems.
2.0 Interpretation
2.1 In these specifications,
| Adjustment | means a change in the value of any of a device's sealable calibration or sealable configuration parameters. |
| Adjustment Mode | means an operational mode of a device which enables the user to make adjustments to sealable parameters, including changes to configuration parameters. |
| Audit Trail | means an electronic count and/or information record of the changes to the values of the calibration or configuration parameters of a device. |
| Calibration Parameter | means any adjustable parameter that can affect measurement or performance accuracy, and due to its nature, needs to be updated on an ongoing basis to maintain device accuracy. |
| Configuration Parameter | means any adjustable or selectable parameter for a device feature that can have an affect on the accuracy of a transaction or can significantly increase the potential for fraudulent use of the device and, due to its nature, needs to be updated only during device installation or upon replacement of a component. |
| Enabling/Disabling Sealable Hardware
|
means physically sealable hardware, such as a two-position switch, located on a remotely configurable device, that enables and inhibits the capability to receive adjustment values or changes to sealable configuration parameters from a remote source. |
| Event | means an action in which one or more changes are made to configuration parameters, or adjustments are made to one value (or a set of values) for a calibration parameter, while in the adjustment mode. |
| Event Counter | means a non-resettable counter that increments once for each time the mode that permits changes to sealable parameters is entered and one or more changes are made to sealable calibration or configuration parameters of a device. |
| Event Logger | means a form of audit trail containing a series of records where each record contains the number from the event counter corresponding to a change to a sealable parameter, the identification of the parameter that was changed, the time and date when the parameter was changed and the new value of the parameter. |
| Physical Seal | means a physical mechanism, such as lead and wire, used to seal access to a device's adjustable parameters that require to be sealed. |
| Remote Configuration Capability | means the ability to adjust a weighing or measuring device or change its sealable parameters from or through some other device which is not itself necessary to the operation of the weighing or measuring device or is not a permanent part of that device. |
| Remote Device | means a device that (1) is not required for the measurement operation of the primary device or computing the transaction information in one or more of the available operating modes for commercial measurements, or (2) is not a permanent part of the primary device. In the context of this paper, a remote device has the ability to adjust the weighing or measuring device or change its sealable configuration parameters. |
| Remotely Configurable Device | means any weighing or measuring device with remote configuration capability that permits sealable configuration or calibration parameters to be deleted, appended to, modified, or substituted in whole or in part by downloading over any type of communications link from another device, such as a geographically local or remote console or computer, whether or not the secondary apparatus is part of the network connecting the devices. |
| Seal means | as a verb, to make a device secure so that access to adjustments and other sealable parameters will be detectable. |
| Sealable Parameter | means calibration and configuration parameters that are required to be sealed. |
| Unrestricted Access to Sealable Parameters | means that a physical security seal is not present, so that access to sealable parameters is available from a remote device at any time at the request of an authorized operator subject to the operating status of the weighing or measuring device. |
3.0 Categories of Devices
3.1 Category 1: A device that does not have remote configuration shall be sealed as described in the appropriate section of Table A.
3.2 Category 2: A device offering remote configuration capability for its sealable parameters and providing enabling/disabling hardware to control remote configuration use shall be sealed as described in the appropriate section of Table A.
3.3 Category 3: A device that provides unrestricted access to its sealable parameters shall be sealed as described in the appropriate section on Table A.
Table A: Categories of Devices and Methods of Sealing
Categories of Device |
Methods of Sealing |
Category 1: No remote configuration capability. |
Physical seal or two event counters: one for calibration parameters and one for configuration parameters. |
Category 2: Remote configuration capability but access is controlled by physical hardware. |
Enabling/disabling hardware access for remote communication must be located at the device and must be sealed using a physical seal or two event counters: one for calibration parameters and one for configuration parameters. |
Category 3: Remote configuration capability may be unlimited or controlled by a software switch (ex. password). |
An event logger is required in the device. |
4.0 Event Counters
4.1 The minimum form of audit trail shall consist of two event counters: one for calibration parameters and one for configuration parameters.
4.2 Each event counter shall have a capacity of at least 1000 values (ex. 0 to 999).
4.3 An event counter for calibration parameters or configuration parameters shall increment only once regardless of the number of changes made while in the adjustment mode. If the mode is accessed and no changes are made, this does not constitute an event and the counter shall not increment.
5.0 Event Loggers
5.1 The event logger shall contain the following information, as a minimum:
i) a count of the events;
ii) date and time;
iii) parameter identification, and
iv) new value.
5.1.1 The information described in section 5.1 shall be automatically entered in the event logger by the device each time a sealable parameter is changed.
5.1.2 Additional relevant information is permitted, such as the identification of the person who made the adjustment or the old value of the parameter that was changed. Information that is not directly related to the changes to sealable parameters, such as transaction data, operator inventory records, or shift totals shall be excluded when event logger contents are displayed or printed.
5.1.3 The event counter described in section 5.1 shall increment once for each change to a sealable parameter since each new value must be retained in the event logger.
5.1.4 The date referred to in section 5.1 shall include the year, month and day; the time shall include the hour and minutes. This information shall be presented in an recognizable format.
5.2 A hard-copy printout of the contents of the event logger shall be available upon demand from the device or from an associated device on site.
5.3 An event logger shall have the capacity of at least ten times the number of sealable parameters; however, not more than one thousand events are required to be retained for all parameters combined.
5.3.1 When the storage memory of the event logger has been filled to capacity, any new event will cause the oldest event to be deleted.
5.3.2 The event counter used in an event logger shall continue to increment to capacity although the event logger may retain fewer records than the count capacity of the event counter.
6.0 Centralized Event Logger
6.1 A centralized event logger may be used when several "satellite" devices are interfaced to a host computer or other host instrument with remote configuration capability.
6.2 When changes to sealable parameters are made at the device, rather than through the host instrument containing the centralized event logger, the changes shall be transferred to and maintained in the centralized event logger.
6.3 It shall not be possible to circumvent the device containing the centralized event logger. If the event logger is inhibited, or disconnected, the attached network of devices shall be inoperable and impossible to adjust electronically when in the network configuration.
6.4 When the same values for a change to a sealable parameter are sent from the host instrument to several satellite devices, this shall be considered a single event.
6.5 When changes to sealable parameters are made to individual devices, the centralized event logger shall identify both the device and the parameter that was changed.
6.6 A device installed in a "stand-alone" operation must have the minimum form of audit trail required by Table A .
7.0 Category 2 Devices - Remote Configuration Mode
7.1 When a remotely configurable device is in remote configuration mode, the device shall either:
- not indicate or record (if equipped with a printer) values; or,
- provide a clear and continuous indication that the device is in remote configuration mode. Any printed ticket or receipt shall include a message with each ticket or receipt that the device is in an adjustment mode.
Note:
A "clear and continuous indication" must discourage the use of the device for normal transactions when in an adjustment mode. This may consist of a partial obscuring of the indication, an alternate display message, or some other obvious indication. The lighting of an annunciator is not sufficient. If values can be printed when in an adjustment mode, the system shall record a message to indicate that the device is in an adjustment mode.
8.0 Audit Trail Integrity
8.1 The audit trail shall be:
i) stored in non-volatile memory and retained for at least 30 days if power is removed from the device; and
ii) protected from unauthorized erasure, seizure, substitution, or modification.
9.0 Audit Trail Access
9.1 The inspector shall have ready access to audit trail information for the purpose of printing or viewing its contents.
9.2 Access to the audit trail for the purpose of review shall be separate from the calibration and configuration modes.
9.3 Access to the audit trail for the purpose of review shall not affect the normal operation of a device before or after accessing the information.
9.4 Access to the audit trail information shall not require the removal of any parts of a device other than normal requirements to inspect the integrity of a physical seal.
Note: A key (for a panel lock, for example), is acceptable to gain access and view the contents of the audit trail. Such access may be through the "supervisor's mode" of a device.
10.0 Displayed and Recorded Information
10.1 The displayed and/or printed form of the audit trail shall be readily interpretable by the enforcement official.
10.2 The information contained in the audit trail shall be displayed and/or printed in order, from the most recent event to the oldest event. The device shall be capable of displaying all the information for a single event on one line at one time, or it shall display the information in readily understandable blocks of data.
11.0 Sealable Parameters
11.1 Subject to subsections 11.2, 11.3, 11.4, and 11.5, calibration and configuration parameters that can affect measurement performance of a device, the accuracy of a transaction, or can significantly increase the potential for fraudulent use, shall be sealed.
Note: The need to seal specific features also depends upon:
i) The ease with which the feature or the selection of the feature can be used to facilitate fraud; and
ii) The likelihood that the use of the feature will result in fraud not being detected.
11.2 The adjustment mode containing sealable parameters shall access only sealable parameters. Features and functions that are routinely used by the operator as part of the device operation, such as setting unit prices and maintaining unit prices in price look-up (PLU) codes stored in memory, are not sealable parameters. Access to these features shall be separate from the access to sealable parameters.
11.3 When the selection of a parameter or a set of parameters will result in device performance that will obviously be in error, such as the selection of parameters for a different country, the selection of the parameter or set of parameters in question is not required to be sealed.
11.4 Access to any programming mode or menu that allows individual characteristics of a device to be selected and changed must be sealed.
11.5 Any physical act, such as cutting a wire and physically repairing the cut to reactivate the parameter, is considered an acceptable way to select parameters without requiring a physical seal or an audit trail.
11.6 A list of adjustments, features and parameters that require to be sealed is found in Table B. This list is not intended to be all inclusive.
Note: A device manufacturer must demonstrate that any features that are not sealed will not affect the metrological performance of the device.
Table B: Sealable Parameters
Non-Automatic Weighing Devices |
Liquid Measuring Devices |
Calibration Parameters Zero (coarse). Sensitivity (span). Linearity correction points.
Configuration Parameters
Motion detection (on/off, band ). Scale interval (value of d or location of decimal). Number of scale divisions. Range of overcapacity. Automatic zero setting mechanism (on/off and range of a single step). Zero and automatic zero setting mechanism total range (if the range can be set for more than 4% and if this increases the device weighing capacity). Filter (number samples averaged for weight readings). Filter (averaging time for weight indications). Units of measurement (if not displayed or printed on the primary register). |
Calibration Parameters Mechanical accuracy adjustor, electronic meter factor or any other type of accuracy adjustment parameter and associated flow rate if applicable. Mass flow meter zero and span adjustments.
Configuration Parameters
Temperature, pressure and density or other auxiliary sensor zero, span and offset settings. Units of measurement (if not displayed or printed on the primary register). Temperature compensation table, liquid coefficient of expansion or, compressibility factors or tables used if not indicated on a printed ticket. Liquid density (if not displayed or printed on the primary register). Vapour pressure of liquids if used in calculations to establish quantity. Meter or sensor temperature compensation factors if used. False or missing pulse limit for dual pulse systems. Automatic temperature, pressure, or density (ATC, APC, ADC) compensation on/off status. Sensor auto/manual data input modes if not apparent when the device is used or not printed on a ticket. Dual pulse checking feature on/off status. Flow control settings (optional). Filtering constants. |
11.7 Sealable parameters for conveyor belt scales shall include those listed for non-automatic weighing devices as well as the following:
i) Length of the weighing element;
ii) Number of pulses per unit of length (or equivalent);
iii) Maximum belt speed;
iv) Maximum/minimum instantaneous load (units of mass), or maximum/minimum rate of product flow (mass per unit length);
v) Finest increment of registration of the Master Weight Totalizer;
vi) Alarm levels;
vii) Any associated filtering functions;
viii) Summing box; and
ix) Displacement transducer casing.
11.8 Sealable parameters for discontinuous totalizing automatic weighing devices, such as bulkweighers and automatic hopper scales shall include those listed for non-automatic weighing devices as well as interlocks (software or hardware, control panel, etc.) that monitor level sensors, limit switches, motion detectors or any other interlocks.
11.9 Sealable parameters for in-motion rail weighing systems shall include those listed for non-automatic weighing devices as well as the following:
i) Maximum and minimum weighing speed for legal for trade weighing;
ii) Restrictions on train travel direction for legal for trade weighing (if applicable);
iii) Maximum number of wagons that shall be weighed as part of a legal for trade weighing (if such a limitation is imposed on the device); and
iv) Any associated filtering functions.
Devices to be tested for influence factors and disturbances
Device Type |
Temp. Accuracy |
Temp. |
Barometric Pressure |
Warm-up |
Short Time |
Power |
Creep |
Creep |
Burst |
Damp Heat |
Electronic Scales |
X |
X |
X |
X |
? |
X |
X |
X |
? |
X |
Electronic Scales |
|
|
X1 |
X |
? |
X |
X |
X |
? |
|
Electronic Indicators2 |
X |
X |
|
X |
? |
X |
|
|
? |
X |
Electronic Weighing Elements Max ≤ |
X |
X |
X1 |
X |
|
|
X |
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Note: the 1000 kg capacity limit for electronic scales is due to the actual dimension of the environmental chamber needed to perform influence factor tests. This limit would change should the Laboratory acquire a larger environmental chamber.
Recommended Test Sequence
Phase 1: Tests performed at ambient conditions (20°/50% RH)
A. The device is configured, pre-tested and calibrated as close to zero error as possible. No other calibration is permitted before the device is moved to the environmental chamber.
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Exercise the device (3 times up to at least 90% Max)
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Load discrimination near zero and near capacity
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Increasing and decreasing load tests
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Repeatability, return to zero tests
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Eccentricity (Shift/corner tests)
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Tilting (off level) and suitability of level indicator tests
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Power interruption test
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AC/DC voltage variation tests
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RFI test, (27 and 460 MHz)
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Susceptibility to magnetism test (if necessary)
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Warm up test
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Burst test
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Electrostatic Discharge test
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Short Time Power reduction test
Phase 2 Temperature variation effect on the device performance
B. The device is moved to the environmental chamber set at ambient temperature, installed, pre-tested and re-calibrated if necessary. During the tests, no adjustment is permitted.
First : tests at 20°/50% RH
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Condition the DUT
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Exercise the DUT (3 times up to at least 90% Max)
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Increasing and decreasing load test
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Recovery period4
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Creep test
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Recovery period
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Creep-Return-to Zero
Passage from 20° to -10°
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Temperature effect on no-load indication
Second : test at -10°
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Condition the DUT (2 hours minimum after temperature stabilization)
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Exercise the DUT
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Increasing and decreasing load test
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Recovery period
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Creep test
Passage from -10° to 40°
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Temperature effect on no-load indication
Third: tests at 40°/50% RH
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5Condition the DUT (2 hours minimum after temperature stabilization)
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Exercise the DUT
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Increasing and decreasing load test
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Recovery period
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Creep test
Passage from 40° to 20°
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Temperature effect on no-load indication
Fourth: tests at 20°/50% RH
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Condition the DUT (2 hours minimum after temperature stabilization)
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Exercise the DUT
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Increasing and decreasing load test
Damp Heat at 40°/85% RH
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Condition the DUT
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Wait 48 hours
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Increasing and decreasing load test
Damp Heat at 20°/50% RH
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Condition the DUT (2 hours minimum after temperature stabilization)
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Exercise the DUT
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Increasing and decreasing load test
Phase 3: Permanence test at ambient conditions (20°/50% RH)
C. The device is moved to the permanence testing machine, installed, pre-tested and re-calibrated if necessary.
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Load discrimination test near zero and near capacity
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Increasing and decreasing load tests
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Repeatability, return to zero tests
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Eccentricity (Shift/corner tests)
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Permanence test (25000 applications)
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Increasing and decreasing load test
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Permanence test (25000 additional applications)
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Increasing and decreasing load test
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Permanence test (25000 additional applications)
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Increasing and decreasing load test
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Permanence test (25000 additional applications)
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Load discrimination test near zero and near capacity
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Increasing and decreasing load tests
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Repeatability, return to zero tests
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Eccentricity (Shift/corner tests).
Part 3 - Performance Tests
LG-3.01 Linearity, Hysterisis and Repeatability at Ambiant Temperature
Application
This test is intended for complete mechanical or electronic weighing devices, indicating and load receiving/weighing elements tested separately.
Settings
1. AZSM may be in operation during the tests. It must be set to the lowest value; if zero is the lowest selectable value, it will be set to zero. However, the amount that the AZSM may track at once may not be set to a value larger than 0.6 e which is the maximum value allowed by the Specifications.
2.1 If the IZSM range does not exceed 20% of the device capacity, tests will be performed with the IZSM set at the upper limit of its range. The IZSM range of an indicating element tested separately may not exceed 20%.
2.2 If the IZSM range exceeds 20%, tests will be performed twice. A first series of tests using the lighter platter provided by the applicant, and the second series with the IZSM set to the upper limit of its range.
3. The weighing device must be levelled, adjusted as to zero error as possible and pre-loaded (exercised) 3 times up to at least 90% Max.
4. The device must be configured for the maximum capacity and smallest verification scale interval for which the approval is sought.
5. If so equipped, the "enhance resolution feature" of the device will be used during the tests. If this feature is not available, use the small weight method to determine the device errors before rounding (internal errors). This is not necessary if the errors are marginal.
6. This test is performed at ambient temperature (≈ 20°C, or at the mid point of the temperature range if significantly different from 20°C, and at relative humidity of ≈ 50%.
Procedure
- Pre-condition the device: the DUT must have reached a stable temperature at ambient condition.
- Set the device to zero.
- Perform a minimum of three increasing and decreasing load tests to capacity using at least 5 known test weights. Loads must be centred on the load receiving element. Loads must be selected in relation to the device capacity, the value of the verification scale interval and the turning points of the tolerances. Determine the true error before rounding (internal or true errors). Record the results.
Multiple range weighing devices
- Perform a minimum of three increasing and decreasing load tests using at least 5 known test weights in each individual range. Record the results.
- Load the scale to the maximum capacity of the highest range (or manually select the highest range and then load the device to capacity); Remove the load: the indications should return to zero immediately. Switch the device to the lowest range immediately ( If the switch over is automatic, the device should have returned to the lowest range automatically). Note the indication near zero at the time the device switches to the lowest range. Observe the weight indication for 5 minutes. Record any changes.
Interpretation of Results
Reference: Sections 9, 10, 11,12, 13, and 17 of the Specifications
- All functions must operate as designed and as intended.
Linearity and hysteresis
- Each individual result must be within the tolerance envelope as prescribed by the Specifications.
Return to zero
- The device must return to zero from Max within 0.5 e for a complete device, and within 0.35 e for an indicating or load receiving/weighing element tested separately.
- A multiple range device must return to zero from Max i within 0.5e i . After returning to zero from any load greater than Max 1 and immediately after switching to the lowest weighing range, the indication near zero shall not vary by more than 0.5e 1 during the following five minutes.
Repeatability
- Compare the results for each individual load of increasing and decreasing tests. The maximum difference between the results for the same load must not exceed the in-service limits of error as prescribed by the Specifications. In addition, all results must be within tolerances.
Note that:
- the error of any single weighing result must not exceed the maximum limit of error for the given load.
- a major element (module) tested separately and that is the only component of the weighing system subject to measurement errors due to disturbance or influence factors is allowed entire applicable limits of error (i.e. a weighing element which produces an output digital signal readable by a computer).
Application
Load discrimination tests are performed on complete electronic or mechanical non automatic scales, and weighing elements tested separately using a high precision electronic indicator (Resolution must be at least ten times the DUT resolution). This test is not applicable to electronic indicators tested separately.
The load discrimination test is used to determine whether the device is capable of sensing a small change of load and of changing its registration accordingly. Frictional forces, binding or system inertia can prevent a mechanical device from sensing the prescribed "Load Discrimination Test Load". Frictional forces, binding, the use of oversized (capacity) load cells, the use of an electronic indicator with an inadequate display sensitivity
(
Volts/Display Digit) or inadequate digital filter algorithms could cause an electronic weighing device to fail to detect the addition of the prescribed "Load Discrimination Test Load".
Settings
1. AZSM may be in any status. This test is performed at the same time the increasing and decreasing load test is performed.
2.1 If the IZSM range is limited to 20% of Max, the test will be performed with the IZSM set at the upper limit of its range.
2.2 If the IZSM range exceeds 20%, tests will be performed twice: with the lighter platter provided by the applicant, and with the IZSM set to the upper limit of its range.
3. The device must be configured for the maximum capacity and smallest verification scale interval for which the approval is sought.
4. This test is performed at ambient temperature (≈ 20°C, or at the mid point of the temperature range if significantly different from 20°C).
5. The test must be performed at zero load (or near zero) and near Max.
A. Automatic Digital Indicating Devices
Procedure
A.1 If necessary, put a small load on the platter to bring the scale out of its AZSM range. The indication is near zero.
A.2 Successively add small weights equal to 1/10 d until the ZU is reached; the indication should be alternating between two values; remove one small weight to obtain a solid indication; the indication is at the high point of the scale interval. Record the indication.
A.3 Smoothly add a load equal to 1.4 d. Record the indication.
A.4 Repeat the test near the maximum capacity.
(See points 2,1 and 2,2 above
Note: The test can also be done by removing the 1.4 d test weight. To do so, bring the indication right above the ZU and then remove the 1.4 d load.
Interpretation of Results
Reference: Section 15 of the Specifications.
The addition or removal of the 1.4 d test load must cause a change in the indication of 2 d.
B. Automatic Analogue Indicating Devices
Procedure
B.1 At the no load condition, press on the platter to generate motion of the indicating element (pointer). Allow the indicator to stabilize.
B.2 Smoothly add (or remove) a load equal to 1.4 d and allow the indicating element to stabilize. Record the indication.
B.3 Repeat the test near maximum capacity.
Interpretation of Results
Reference: Section 15 of the Specifications.
The addition or removal of the 1.4 d test load must cause a change in the indication of 1 d.
C. Non Automatic Indicating Devices - Beam Scales With no Additional Means of Indication
Procedure
C.1 Set the device to zero (beam in horizontal position at mid distance between the trig loops or the limiting stops).
C.2 Add or remove a load equal to 1 d (in-service limit of error) when the test is performed near zero.
C.3 Repeat the test near maximum capacity. Add or remove a small load corresponding to the in-service limit of error applicable to the load on the platter, without exceeding 2 d.
Interpretation of Results
Reference: Section 14 of the Specifications.
The addition or removal of the test load must cause the weighbeam to change from the center position to the outer limit of the trig loop or limiting stops.
D. Non Automatic Indicating Devices - Beam With Additional Indicating Means (Over/Under Indicator having graduations without values)
Procedure
D.1 Set the device to zero.
D.2 Add or remove a load equal to 1 d (in-service limit of error) when the test is performed near zero.
D.3 Repeat the test near maximum capacity. Add or remove a small load corresponding to the in-service limit of error applicable to the load on the platter, without exceeding 2 d.
Interpretation of Results
Reference: Section 14 of the Specifications.
The addition or removal of the test load must cause the position of the indicator to change by the distance indicated below:
i) 1 mm for Class I and II devices;
ii) 2 mm for Class III and IIII devices with a Max ≤30 kg;
iii) 5 mm for Class III, III HD and IIII devices with a Max > 30 kg.
- Testing is limited to some canister load cells
- Indicating elements processing only digital information do not have to be tested for compliance with influence factors
- Weighing elements that provide digital signals ("smart" load cells) are considered, for testing purposes, complete electronic devices.
- Recovery periods must last for at least the time required to perform the previous test.
- Measures must be take to avoid condensation on the device
Application
Eccentricity tests are performed on complete devices and weighing elements tested separately. Shift tests are also performed on single point hanging scales if the load receptor is relatively large.
The purpose of this test is to reveal the ability of load cell(s), load cell mounting and check systems of a weighing elements to ignore or compensate for the torsion effects of non axial loads. The purpose of this test is also to ensure that the load cells of electronic scales or the lever of mechanical scales can be adequately "balanced" in order to obtain accurate weighing regardless of the position of the load on the platter.
The device must be capable of weighing accurately despite of changes of position of the test load over the load receiving element.
Settings
1. AZSM may be in any status. When practical, this test can be performed while performing Increasing/Decreasing load tests.
2.1 If the IZSM range does not exceed 20% of the device capacity, tests will be performed with the IZSM set at the upper limit of its range.
2.2 If the IZSM range exceeds 20%, tests will be performed twice. A first series of tests using the lighter platter provided by the applicant, and the second series with the IZSM set to the upper limit of its range.
3. The device must be set for the maximum capacity and smallest verification scale interval for which the approval is sought.
4. If so equipped, the "enhance resolution feature" of the device will be used during the tests. If this feature is not available, use the small weight method to determine the device errors before rounding.
5. This test is performed at ambient temperature (≈ 20°C); or at the mid point of the temperature range if significantly different from 20°C.
Procedure
A.Bench , Counter or Hanging Scales, other Small Platform Scales, and Equal Arm Scales with load receiving elements having no more than four points of support.
A.1 Stabilize the device at nominal conditions; zero the device.
A.2 Apply a load equal to ≈ 1/2 Max on the center of the platter. Record the indication.
A.3 Apply the same test load on the device in such a manner that the center of gravity of the test load lies approximately at the center of one of the numbered target boxes in the following illustrations. Record the indication.
A.4 Proceed in the same manner with the other points of application. Record the indication.
Note: In the case of weighing elements that comprise 4 load cells (one at each corner), a load of 1/4 Max applied to each corner is also a valid test.
Bench, Counter or Hanging Scales
(one single load cell)
Other Platform Scales
(More than one load cell)
Equal Arm Scales
B) Monorail scales
B.1 Stabilize the device at nominal conditions; zero the device.
B.2 Apply a rolling load corresponding to the usual rolling load, the heaviest and the most concentrated one which may be weighed, but not exceeding 0.8 times Max at different points of the load receiving element.
B.3 Record the indications.
Monorail Scales
C) Tank or Hopper Scales
C.1 Stabilize the device at nominal conditions; zero the device.
C.2 Use a load of at least 1/10 without exceeding 1/4 of Max. Apply the load to each point of support. Care must be taken to keep the center of gravity of the load within the parameter formed by the points of support; otherwise the tank or hopper could tilt or shift.
C.3 Record the indications.
Tank or Hopper Scales
Interpretation of Results
Reference: Sections 9, 10, 11, 12 and 14 of the Specifications
The difference between the results for different position of the load must not exceed the absolute value of the In-Service limit of error for that load; and
Each individual results must be within the limits or error permitted.
LG-3.04 Tilting (Off Level Position)
Application
This test is performed on any complete portable or movable devices or weighing elements tested separately, that are of a type other than suspended, and that are not equipped with a suitable level indicating means. Devices aimed are: bench and counter scales, floor scales, weighing systems mounted on a vehicle (On-board weighing systems for NH3, on-board waste weighing systems, scales mounted on lift trucks). "Portable" vehicle scales do not fall into this category. The purpose of this test is to ensure that the performance is not affected when the device is off level.
Settings
1. The AZSM may be activated. It must be set so that the weight value that can be tracked at once does not exceed 0.6 e.
2.1 If the IZSM range does not exceed 20% of Max, the test will be performed with the IZSM set at the maximum of the range.
2.2 If the IZSM range exceed 20%, the test will be performed twice: the first test with the IZSM set to the lowest possible value; the second test with the IZSM set to the to the maximum of its range.
3. If the device has an "enhance" resolution feature, perform the test with that feature activated; or use the small weight method to determine errors before rounding.
5. This test is performed at ambient temperature only.
Procedure for portable or movable scales
Note: The device is tested for accuracy when levelled, first; then off-level tests are performed.
A. The procedure consists of inclining the device in the four directions (+x, -x, +y, -y) using a suitable support. The tests is performed when the device is off level by the lesser of:
a) 3 degrees; or
b) the maximum angle at which the device still provides an indication or registration.
B. For each of the four inclinations, set the device two zero and perform an increasing and decreasing load test.
Note:
It is not necessary to proceed further if at the first inclination the device does not perform within the prescribed limits of error.
Interpretation of Results
Reference: Section 9, 10, 11 and 22 of the Specifications
The device meets the requirements if it performs within prescribed limits of error when off level.
Note:
If the device can not perform within the prescribed limits of error, it must be equipped with a suitable level indicating means permanently installed.
Procedure for On-Board Weighing Systems
(Level Testing)
- With the vehicle resting on a level surface, visually inspect, checking for possible binding and additional items secured to the device that may have an effect on accuracy (e.g. mudflaps and fenders must be secured to the frame of the vehicle, not the device).
- Perform load discrimination tests near zero and at capacity; increasing and decreasing load tests; section/corner tests; repeatability; blanking at capacity and motion detection; return to zero; etc.. The device must perform within the prescribed limits of error.
( Off Level)
- Visually inspect the device while performing the following tests to ensure that the inclination does not cause a shift that may affect the device accuracy.
- Elevate the front or rear wheels to 3 degrees or the maximum inclination at which a weight indication is still provided. Perform the tests indicated in D above, except the section and repeatability test.
- Elevate either the driver side or passenger side to 3 degrees or the maximum inclination at which a weight indication is still provided. Perform the tests indicated in D above, except the section and repeatability test.
- Elevate a single rear wheel combination until the side to side inclination is 3 degrees or the point at which a weight indication is still provided. This test cause the frame to twist and will reveal defects in poorly constructed devices. Perform the tests indicated in D above, except the section and repeatability test.
- Scales mounted on lift trucks (or similar vehicles) must blank their indications when the lift truck is moving, unless the scale can provide an accurate weight indication. Perform an accuracy (in-motion) test using different loads within the capacity range of the device. The test must simulate actual conditions of use.
Interpretation of the Results
Reference: Section 9, 10, 11 and 22 of the Specifications
The device meets the requirements if :
- it provides a weight indication when off level up to at least 3 degrees;
- it performs within the prescribed limits of error when off level by the larger of 3 degrees or the maximum angle at which it still provides a weight indication;
- it blanks its indications and prevent the recording of weight values when it ceases to perform within tolerances.
- in the case of a scale mounted on a lift truck, it provides weight indications within the permissible limits of error while the lift truck is moving, or blanks its indications.
LG-3.05 Suitability of the Level Indicator
Application
This test is intended for complete portable or movable devices and weighing elements whose performance is affected when off level. Such devices must be equipped with a suitable level indicating means. This test is to ensure that the level indicating means is sensitive enough to accurately indicate the limit of inclination at which the device ceases to perform within tolerances.
Settings
1. The AZSM may be activated. It must be set so that the weight value that can be tracked at once does not exceed 0.6 e.
2.1 If the IZSM range of the device does not exceed 20% of Max, the test will be performed with the IZSM set at the maximum of the range.
2.2 If the IZSM range exceed 20% of Max, the test will be performed twice: the first test with the IZSM set to the lowest possible value; the second test with the IZSM set to the to the maximum of its range.
3. The device must be levelled using the level indicating means, and adjusted to as close to zero error as possible.
4. If the device has an "enhance" resolution feature, perform the test with that feature activated; or use the small weight method to determine errors before rounding.
5. This test is performed at ambient temperature only.
Procedure
A) Incline the DUT in one direction (arbitrary referred to as -x) up to the point of limit where the level indicating means still indicates a level condition or at least 2/1000 (.12 degree) whichever is greater.
B) Set the device to zero if necessary; perform an increasing and decreasing load test. If necessary, use the small weight method to find errors before rounding. Record the results.
C) Repeat the test described in B) for the other three inclinations (+x, -y, +y) (See the following illustrations).
Interpretation of Results
Reference: Sections 9, 10, 11 and 22 of the Specifications
The device meets the requirements if, at the limits of inclination in all four directions, it performs within applicable limits of error.
Application
This test is intended for any electronic devices and electronic major components. The purpose of this test is to ensure that weight indications provided by a device while it warms up are accurate.
Settings
- The AZSM may be activated. It must be set to the lowest value; if zero is the lowest selectable value, it will be set to zero. The amount that the AZSM may track at once may not be set to a value larger than 0.6 e which is the maximum value allowed by the Specifications.
- The AZSM will be set to the maximum of its range.
- The device must have been set to as close to zero error as practicable.
- If the device has an "enhance" resolution feature, perform the test with that feature activated; or use the small weight method to determine errors before rounding.
- This test is performed at ambient temperature only.
Procedure
- Turn off and disconnect from the power source the DUT for a period of at least eight (8) hours (i.e. disconnect a wall mount transformer or pull the plug of AC device; remove the batteries of a DC device).
- Re-connect the DUT to the power source and switch it "on".
- Record the first available indication (i.e. the first indication that can be used for the purpose of the transaction).
- Set the device to zero.
- Apply a load equal to at least 70% of Max.
- Record the indication.
Interpretation of Results
Reference: Sections 9, 10, 11, 31 and 32 of the Specifications
The device meets the requirements if the first weight indications available are within the applicable limits of error. Otherwise, weighing operations (printing or indicating weight values) must be inhibited during the warming up period.
Application
This test is performed on complete electronic scales and electronic indicators tested separately. This test is to ensure that momentary power failures that can occur during weighing operations will not lead to measurement errors that can not be easily detected. This test also apply to battery-powered devices where the battery is replaceable or rechargeable.
Settings
Removable or rechargeable battery must be disconnected; the AZSM may be in any status.
Procedure
- Place a load on the load receiving element and zero the device (by activating the non-automatic zero setting mechanism).
- Place an additional load on the load receiving element and note the registration.
- Unplug the DUT by pulling the plug and, in no less than five (5) and no more than ten (10) seconds, restore the power to the DUT and record the manner the scale returns to operation. Note the registrations.
- Repeat the test, but this time interrupt the power using the power switch of the DUT..
- Repeat the test with a Keyboard or Platter tare entered; repeat the test with preprogrammed tares entered (i.e. tares associated to PLU codes); repeat the test with an "in-bound" weight entered.
Interpretation of Results:
Reference: Section 9, 10, 11, 31, and 32 of the Specifications.
The DUT is deemed to comply with the requirements if, after interrupting and restoring the power to the DUT, the registration has:
| 1. |
and |
| 2. |
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Application
This test is performed on any complete electronic devices or major electronic components powered from an AC source. Voltage variations are susceptible to occur during the normal use of devices. The purpose of this test is to ensure that voltage variations does not affect the device performance.
Settings
1. AZSM may be in operation during the tests. It must be set to the lowest value; if zero is the lowest selectable value, it will be set to zero. The amount that the AZSM may track at once may not be set to a value larger than 0.6 d which is the maximum value allowed by the Specifications.
2.1 If the IZSM range does not exceed 20% of Max, tests will be performed once with the IZSM set at the upper limit of its range.
2.2 If the IZSM range exceeds 20% of Max, tests will be performed twice: a first series of tests using the lightest platter provided by the applicant, and the second series with the IZSM set to the upper limit of its range.
3. The weighing device must be levelled to its reference position.
4. The device must be set for the maximum capacity and smallest verification scale interval for which the approval is sought.
5. If so equipped, the "enhance resolution feature" of the device will be used during the tests. If this feature is not available, use the small weight method to determine the device errors before rounding.
6. This test is performed at ambient temperature (≈ 20°C) or at the mid point of the temperature range if significantly different from 20°C and ≈ 50% RH.
7. Power source must be stable to within ± 2%
Test Procedure
- Let the Power Supply and the DUT warm up for the minimum time recommended by the manufacturer.
- Set the voltage at the nominal value.
- Perform an increasing and decreasing test and record the results.
- Activate the device functions to ensure they operate normally (tare, printing, motion detection, etc.)
- Record the following data: a) time, b) temperature, c) relative humidity, d) voltage, e) loads, f) indications, g) errors, and h) note any malfunctions of the features.
- Decrease the voltage to the minimum voltage specified; repeat steps C), D) and E).
- Increase the power supply voltage to the maximum voltage specified; repeat steps C), D) and E).
Maximum and minimum voltage specified
- If the nominal voltage is not indicated on the marking plate, 117 volts or 225 volts, as the case may be, is deemed to be the nominal voltage. Then, the minimum and maximum voltage are 100 volts or 191 volts (-15%) and 129 volts or 247,5 volts (+10%) respectively.
- If the marking plate indicates a nominal voltage other than 117 volts, the indicated voltage will be considered as the nominal voltage. The minimum and maximum voltage will be calculated from the nominal voltage indicated on the plate.
- If a voltage range is indicated ( i.e. 100 volts to 130 volts), the mid point of the range will be taken as the nominal voltage. The device will be tested to the greater of: 1) the nominal voltage -15% / +10% or 2) the voltage range indicated on the plate.
- If the device ceases to indicate weight values while the voltage is well within the -15% / +10% range limits, the tests will be performed at the limits of indication.
Interpretation of Results
Reference: Section 9, 10, 11 and 27 of the Specifications
The DUT is deemed to have met the requirements if, during the voltage variations, the device:
a) operates within the prescribed limits of error and all the functions operate normally; or
b) ceases to display weight and price values and prevents the transmission and storage of data.
Application
This test is performed on any complete electronic devices or major electronic components that operate from a DC power source (Batteries or other DC sources). Voltage variations are susceptible to occur during the normal use of devices. The purpose of this test is to ensure that voltage variations does not adversely affect the device performance and normal operating characteristics. DC power operated devices must continue to operate normally despite of a power reduction to the point where no weight indication is provided and power increase by 10% of the nominal value.
Settings
1. AZSM may be in any status. If "on", it must be set to the lowest value; if zero is the lowest selectable value, it will be set to zero. The amount that the AZSM may track at once may not be set to a value larger than 0.6 d which is the maximum value allowed by the Specifications.
2.1 If the IZSM range does not exceed 20% of Max, tests will be performed with the IZSM set at the upper limit of its range.
2.2 If the IZSM range exceeds 20%, tests will be performed twice:. a first series of tests using the lighter platter provided by the applicant, and the second series with the IZSM set to the upper limit of its range.
3. The weighing device must be levelled to its reference position.
4. The device must be set for the maximum capacity and smallest verification scale interval for which the approval is sought.
5. If so equipped, the "enhance resolution feature" of the device will be used during the tests. If this feature is not available, use the small weight method to determine the device errors before rounding.
6. This test is performed at ambient temperature (≈ 20°C) or at the mid point of the temperature range if significantly different from 20°C and ≈ 50% RH..
7. Power source must be stable to within ± 2%
Test Procedure
- Let the Power Supply and the DUT warm up for the minimum time recommended by the manufacturer.
- Set the voltage at the nominal value.
- Perform an increasing and decreasing test and record the results.
- Activate the device functions to ensure they operate normally (tare, printing, motion detection, etc.)
- Record the following data: a) time, b) temperature, c) relative humidity, d) voltage, e) loads, f) indications, g) errors, and h) note any malfunctions of the features.
- Decrease the voltage until the device ceases to provide a weight indication. Increase the voltage until the device resumes the indication; re-zero and repeat steps C), D) and E).
- Increase the power supply voltage up to 10% above the device nominal voltage; re-zero and repeat steps C), D) and E).
Note:
It may be necessary to increase the voltage beyond the limit point of display, and then decrease the voltage in order to be able to reach the lowest voltage at which an indication is provided.
Some devices have an extended voltage range, for instance from 12 to 72 DC volts. In such a case, the device will be tested at the lowest voltage where a weight indication is provided and 10% above the high limit of the voltage range. Interpretation of Results
Reference: Section 9, 10, 11 and 28 of the Specifications.
The DUT is deemed to have met the requirements if during the voltage variations the device:
a) operates within the prescribed limits of error and all the functions operate normally; or
b) ceases to display weight and price values and prevents the transmission and storage of data.
LG-3.10 Immunity to Radiated Electromagnetic Field
Application
This test is performed on any complete weighing devices and major elements that incorporate electronic components susceptible to be affected by radiated electromagnetic fields. This test consists of exposing the device to an electromagnetic field emitted by radio transmitters at frequencies of 27 MHz and 460 MHz with an intensity of up to ≈ 3 V/m.
Note to the Attention of Device Manufacturers
This test method will be used until Measurement Canada acquires the necessary facilities and equipment to perform immunity to radiated electromagnetic field tests over the entire 26 MHz to 1000 Mhz range as recommended by OIML, (R 76-1).
Settings
- The AZSM can be in any status.
- Ensure that the radio transceiver batteries have been fully charged.
- Set the IZSM to the maximum of its range.
- The test is performed at ambient temperature only ( ≈ 20°C and ≈ 50% RH).
- The field strength will be measured using an appropriate field strength meter; results of tests while the field intensity exceed ≈ 3 V/m will not be considered.
- The determination of error before rounding using the small weights method is not necessary.
Procedure
A. Place, on the platter of the device, a load approximately equal to 1/2 Max. Record the value displayed.
B. Perform a summary test at each radio frequencies by bringing the radio antenna close to the DUT at various angles (orientations), above, around and under the device; observe the indication. If the device does not appear to be affected by the RFI, then there is no need to proceed further. If the device is affected, it will be necessary to repeat the test, and this time to measure the field strength at the device.
C. Place the field strength meter in close proximity to the device. Using the handheld radio transmitters, expose the DUT to field strength equal to ≈ 3 V/m. Bring the antenna around, above and under the device, at different angles. Attempt to maintain the field intensity at the device at ≈ 3 V/m. Observe the indication during the test and attempt to print weight values. Record the results. Do not consider the results obtained while the field strength exceeds ≈ 3 V/m.
Interpretation of Results
Reference: Section 30 of the Specifications.
The device meets the requirements if the weight indications and registrations with and without disturbance: 1) do not exceed the value of e, or 2) if the device detects and reacts to a significant fault as follows:
- blanks the indication and prevent the printing of weights; or
- provides an error message and prevent weighings; or
- provides an indication that is completely unstable so that it is not interpreted, or transmitted into memory or to the recording element as a correct measurement value.
LG-3.11 Susceptibility to Magnetism - Magnetic Loads
Application
This test is performed on any complete weighing devices and load weighing elements that incorporate loadcells functioning on the principle of "electromagnetic force compensation.
Settings
1. The AZSM can be in any status.
2. The test is performed at ambient temperature only (≈ 20°C and ≈ 50% RH).
Procedure
Using a ferromagnetic calibrated test weight
- Zero the DUT
- Place on the load receiving element a test weight ≈ 1/2 Max and which is made of a ferromagnetic material (iron or steel). Note the indication and remove the test weight.
- Place on the load receiving element a test weight of the same capacity as that used in step "B" but made of non-magnetic material (brass, austenitic non-magnetic stainless steel). Note the indication and remove the test weight.
Using a ferromagnetic calibrated steel plate
- Zero the DUT.
- Place on the load receiving element a ferromagnetic steel plate. Add a calibrated non magnetic test weight ≈ 1/2 Max (brass, aluminum, austenitic non-magnetic stainless steel). Record the indication.
- Remove the plate; reset the DUT to zero; add a non magnetic plate and test weight of the same mass and note the indication.
Interpretation of Results
Reference : Sections 9, 10, 11 and 30 of the Specifications.
The DUT meets the requirements if the indication obtained using the ferromagnetic material (test weight or plate) is equal to the indication obtained using the non-magnetic material.
LG-3.12 Susceptibility to Magnetism - Ferromagnetic Plate
Application
This test is performed on any complete weighing devices and load weighing elements that incorporate loadcells functioning on the principle of "electromagnetic force compensation.
Settings
1. The AZSM can be in any status.
2. The test is performed at ambient temperature only ( ≈ 20°C and ≈ 50% RH).
3. The DUT must have been tested prior to the following test, and must perform within applicable LOEs.
Procedure
A. Place the DUT on a ferromagnetic plate (steel or iron). Zero the DUT.
B. Perform an increasing and decreasing load test.
Interpretation of Results
Reference : Sections. 9, 10, 11 and 30 of the Specifications.
The DUT meets the requirements if the indication obtained using the ferromagnetic material is within the prescribed LOEs.
LG-3.13 Temperature Effect on Linearity, Hysteresis, Repeatability
Application
This test is intended for any complete devices and major components (including Analogue to Digital signal converters) incorporating electronic components susceptible to be affected by temperature fluctuations. This test is to be performed also on mechanical scales using temperature compensated springs. The purpose of this test is to ensure that devices are able to measure within applicable limits of error at any temperatures between -10°C to 40°C, unless otherwise marked on the device
Not all devices are affected by all of the influence factors, hence not all influence factor tests need to be performed on all devices. For example, indicating elements that processes only digital information (slave display) do not have to be tested for compliance under influence factors.
Settings
- AZSM may be in operation during the tests. It must be set to the lowest value; if zero is the lowest selectable value, it will be set to zero. The amount that the AZSM may track at once can not exceed 0.6d which is the maximum value allowed by the Specifications.
- If a device is provided with an IZSM, the tests will be performed once with the IZSM set to the maximum of its range.
- The weighing device must be levelled to its reference position, be adjusted as close as possible to zero error at ≈ 20°C (or the mid point of the temperature range marked on the device, if significantly different from 20°C) after it has reached his thermal equilibrium with power applied. Except for zero-setting, the device must not be adjusted or re-adjusted at any time during the test.
- The device must be set for the maximum capacity and smallest verification scale interval for which the approval is sought.
- If so equipped, the "enhance resolution feature" of the device will be used during the tests. If this feature is not available, use the small weight method to determine the device errors before rounding.
- This test is performed at the following temperatures:
First round: at nominal temperature (≈ 20°C, or at the mid point of the temperature range if significantly different from 20°C) Second round: at low temperature (- 10°C, or the lower point of the temperature range marked on the device); Third round: at high temperature (+ 40°C, or the higher point of the temperature range marked on the device). Fourth round: at nominal temperature (≈ 20°C, or at the mid point of the temperature range if significantly different from 20°C). - When the environmental chamber has reached the desire temperature, allow a minimum of 2 hours after the DUT temperature has stabilized.
The temperature of the DUT can be monitored by attaching a thermocouple with adhesive tape inside the DUT onto a component of relatively large mass. However, the thermocouple must not be attached to any live component(s) of the DUT. The temperature will be deemed to be stable when the temperature obtained from the thermocouple will have stabilized within ± 1EC. Once stabilized, the temperature obtained from the thermocouple will likely be different than the overall temperature of the environmental chamber. The requirement is only that the temperature of the DUT stabilizes to within ± 1EC.
- 8. Moisture content in the environmental chamber must not exceed ≈ 50% RH at test temperatures.
- 9. The test equipment such as load cell simulators, high precision reference indicators, must be isolated from the test conditions and maintained at constant ambient temperature and humidity.
- 10. Note that the following tests are performed together: temperature effect on linearity and hysteresis, creep and temperature effect on no load condition.
Procedure
- With the DUT switched "on" and in the environmental chamber, stabilize the DUT at ≈ 20°C. Monitor the temperature of the DUT until it has reached stability. Wait an additional 2 hours.
- Exercise (3 times up to at least 90% Max) the DUT; set the DUT to zero.
- Perform at least two increasing and decreasing load tests to capacity using at least five known weights. Loads must be selected in relation to the device capacity, the value of the verification scale interval and the turning points of the tolerances. Determine the true error before rounding. Record the following data: a) time, b) temperature, c) relative humidity, d) loads, e) indications, f) errors, and g) note any malfunctions of the device features.
- Repeat the test sequence at -10°C, + 40°C (or at the lowest and highest temperatures marked on the device). Record the following data: a) time, b) temperature, c) relative humidity, d) loads, e) indications, f) errors, and g) note any malfunctions of the device features.
Additional tests for multiple range weighing devices
- Set the device to zero in the lowest range. Perform three increasing and decreasing load tests using at least 5 known weights.
- Repeat the test for the other ranges.
- Load the scale to the maximum capacity of the highest range (or manually select the highest range and then load the device to capacity); Remove the load: the indications should return to zero immediately. Switch the device to the lowest range immediately ( If the switch over is automatic, the device should have returned to the lowest range automatically). Note the indication near zero at the time the device switches to the lowest range. Observe to weight indication during the next 5 minutes and record any changes.
- Repeat the tests at the other reference temperatures.
- Record the following data: a) time, b) temperature, c) relative humidity, d) loads, e) indications, f) errors, and g) note any malfunctions of the device features.
Interpretation of Results
Reference: Sections 9, 10,11, 12, 13, 17 and 25 of the Specifications
- All functions of the device must operate as designed.
- Linearity and hysteresis Each individual result must be within the tolerance envelope as prescribed by the Specifications.
- Repeatability Compare the results for each individual load of increasing and decreasing tests. The maximum difference between the results for the same load must not exceed the in-service tolerances as prescribed by the Specifications.
- Return to zero The device must return to zero from Max within 0.5 e for a complete device, and within 0.35 e for indicating or load receiving/weighing elements tested separately.
A multiple range device must return to zero from Maxi within 0.5 ei . After returning to zero from any load greater than Max1 and immediately after switching to the lowest weighing range, the indication shall be within 0.5 e1 .
Note that the error of any single weighing result must not exceed the maximum limit of error for the given load.
The following tests are grouped and performed in a pre-determined sequence LG-3.13: Temperature Effect on Linearity, Hysteresis, Repeatability LG-3.14; Creep and Creep-Return-to-Zero LG-3.15; Temperature Effect on the No-Load Indication; See the Recommended on page 3.4
LG-3.14 Creep and Creep- Return-to-Zero
Application
This test is performed on any complete mechanical or electronic weighing device and on any mechanical or electronic weighing element tested separately.
Settings
- AZSM may be in operation during the tests. It must be set to the lowest value; if zero is the lowest selectable value, it will be set to zero. The amount that the AZSM may track at once can not exceed 0.6 e which is the maximum value prescribed by the Specifications.
- If a device is provided with an IZSM, the tests will be performed once with the IZSM set to the maximum of its range.
- The device must be set for the maximum capacity and smallest verification scale interval for which the approval is sought.
- If so equipped, the "enhance resolution feature" of the device will be used during the tests. If this feature is not available, use the small weight method to determine the device errors before rounding.
- The creep test is performed at the following temperatures:
First round: at nominal temperature (≈ 20°C, or at the mid point of the temperature range if significantly different from 20°C) Second round: at low temperature (- 10°C, or the lower point of the temperature range marked on the device); Third round: at high temperature (+ 40°C, or the higher point of the temperature range marked on the device). Fourth round at nominal temperature (≈ 20°C, or at the mid point of the temperature range if significantly different from 20°C). - The creep-return to zero test is performed at ambient ( ≈ 20°C) temperature only.
- Note that these tests are combined with the test performed to assess the temperature effect on linearity and hysteresis.
- The temperature of the DUT must have stabilized to within ± 1°C.
The temperature of the DUT can be monitored by attaching a thermocouple with adhesive tape inside the DUT onto a component of relatively large mass. However, the thermocouple must not be attached to any live component(s) of the DUT. The temperature will be deemed to be stable when the temperature obtained from the thermocouple will have stabilized within ± 1°C. Once stabilized, the temperature obtained from the thermocouple will likely be different than the overall temperature of the environmental chamber. The requirement is only that the temperature of the DUT stabilizes to within ± 1°C.
- Moisture content in the environmental chamber must not exceed ≈ 50% RH at test temperatures.
- The test equipment such as load cell simulators, high precision reference indicators, must be isolated from the test conditions and maintained at constant ambient temperature and humidity.
- The increasing and decreasing load tests must be performed before the creep test and creep-return-to-zero test; a recovery time period equal to the accuracy (increasing and decreasing) test time is permitted before conducting the creep test; the scale should be exercised 3 times up to at least 90% Max before conducting the creep and creep-return-to zero test if an extended period of time has passed since the scale was last tested.
Procedure
Creep test
- Following the increasing and decreasing load test, allow the device to "recover" for a period of time equal to the increasing and decreasing test time. Exercise the scale 3 times up to at least 90% Max.
- Place on the weighing element a load equal to at least 90% of Max, and take a reading 20 seconds after the indication has stabilized. Observe the indication for one hour. Take a second reading.
- Remove the load and wait for the indication to stabilize (no more than 20 seconds). Take a reading.
Note that if a single range device returned to zero within 0.5 e immediately after the removal of the load that has remained on the platter for one hour, there is no need to perform the creep-return-to-zero test.
Creep test on a multiple range device
- The test describe in A, B and C above must be performed for each of the ranges.
Interpretation of Results
Reference: Section 18 of the Specifications.
The device meets the requirements if the difference between the indication obtained 20 seconds after placing the load on the device and the indication observed during the following one hour does not exceed the absolute value of the applicable limit of error for that load.
Creep-Return-to-Zero Test (at ≈ 20°C only)
- Allow the device to recover for a minimum of one hour. Exercise the device with a load of 90% Max.
- Place on the weighing element a load equal to at least 90% of Max. Leave that load on the device for a period of 1/2 hour.
- Remove the load and take a reading as soon as the indication has stabilized (wait no more than 20 seconds).
Creep-Return-to-Zero test on multiple range devices (at ≈ 20°C only)
- Allow the device to recover for a minimum of one hour. Exercise the device with any convenient load that is available.
- Place, on the weighing element, a load equal to ≈ 90% of the maximum capacity of the lowest range. Leave that load on the device for a period of 1/2 hour.
- Remove the load and take a reading as soon as the indication has stabilized.
- Place, on the weighing element, a load equal to at least 90% of the maximum capacity of the highest range. Leave that load on the device for a period of 1/2 hour.
- Remove the load and take a reading as soon as the indication has stabilized (Wait no more than 20 seconds).
- Immediately, switch the device to the lowest range, take a reading of the weight indication. Observe the weight indication for 5 minutes. Record any changes in the weight indication.
Interpretation of Results
Reference: Section 17 of the Specifications.
- The deviation on returning to zero as soon as the indication has stabilized shall not exceed 0.5 e.
- On multi-interval device, the deviation shall not exceed 0.5 e1
- On a multiple range device, the deviation on returning to zero from Maxi shall not exceed 0.5ei ; moreover, after returning to zero from any load greater than Max1 and immediately after switching to the lowest weighing range, the indication near zero shall not vary by more than e1 during the following 5 minutes.
LG-3.15 Temperature Effect on the No-Load Indication
Application
This test is performed on any complete electronic device, any electronic indicator or weighing element tested separately.
Settings
- AZSM must be turned off or set to zero value. If it is not convenient to do so, a small weight (i.e. 10 to 20 graduations) may be placed on the platter to bring the indication off the AZSM range.
- The device must be set for the maximum capacity and smallest verification scale interval for which the approval is sought.
- The test is performed when the environmental chamber's temperature is being changed. The sequence is as follows:
First test: |
from 20°C (or the mid point of the temperature range if significantly different from 20°C) to - 10°C (or the lower point of the temperature range marked on the device); |
Second test: |
from - 10°C to + 40°C (or the higher point of the temperature range marked on the device); |
- The temperature of the DUT must have stabilized to within ± 1°C.
The temperature of the DUT can be monitored by attaching a thermocouple with adhesive tape inside the DUT onto a component of relatively large mass. However, the thermocouple must not be attached to any live component(s) of the DUT. The temperature will be deemed to be stable when the temperature obtained from the thermocouple will have stabilized within ± 1°C. Once stabilized, the temperature obtained from the thermocouple will likely be different than the overall temperature of the environmental chamber. The requirement is only that the temperature of the DUT stabilizes to within ± 1°C.
- Moisture content in the environmental chamber must not exceed ≈ 50% RH at test temperatures.
- The test equipment such as load cell simulators, high precision reference indicators, must be isolated from the test conditions and maintained at constant ambient temperature and humidity.
- The temperature in the chamber is changed at a rate not to exceed 1°C per minute.
- If so equipped, the "enhance resolution feature" of the device will be used during the tests. If this feature is not available, use the error weight method to determine the device errors before rounding.
Procedure
For each test described in 3 above, perform the following procedure:
- Stabilize the DUT at no load condition and at the start temperature for a period of time equal to the time that was required to apply an remove the load during the previous test.
- Zero the DUT, if the AZSM is disabled; or place a small load ( ±5 e) on the platter, and record the registration (Determine the error before rounding using small denomination weights).
- From 20°C to -10°C Lower the temperature of the environmental chamber down to -10°C at a rate not to exceed 1NC per minute.
- When the DUT has reached temperature stability, wait an additional 2 hours.
- Using small denomination weights, determine and record the registration prior to rounding. Record the results
- From -10°C to 40°C Increase the temperature of the environmental chamber up to 40°C at a rate not to exceed 1°C per minute.
- When the DUT has reached temperature stability, wait an additional 2 hours.
- Using small denomination weights, determine and record the registration prior to rounding. Record the results
Interpretation of Results
Reference: Section 24 of the Specifications.
The device meets the requirements if the indication at zero or near zero does not vary by more than:
i) one verification scale interval (e) per 1°C change in temperature, for Class I devices;
ii) three verification scale intervals (e) per 5°C change in temperature, for Class III HD devices; and
iii) one verification scale interval (e) per 5°C change in temperature, for all other device classes.
LG-3.16 Damp Heat, Steady State
Application
This test is intended for any complete electronic weighing devices, and for any electronic weighing elements or electronic indicating elements tested separately. The test consists of exposure of the DUT to a constant temperature and constant relative humidity.
Note that the damp heat steady state test is not presently performed by the Laboratory. MC intents to implement this test in the future.
Settings
- AZSM may be in operation during the tests. It must be set to the lowest value; if zero is the lowest selectable value, it will be set to zero. The amount that the AZSM may track at once can not exceed 0.6 e which is the maximum value allowed by the Specifications.
- If a device is provided with an IZSM, the tests will be performed once with the IZSM set to the maximum of its range.
- The weighing device must be levelled to its reference position, be adjusted as close as possible to zero error at ≈ 20°C (or the mid point of the temperature range marked on the device, if significantly different from 20°C) after it has reached thermal equilibrium with power applied. Except for zero-setting, the device must not be adjusted or re-adjusted at any time during the test.
- The device must be set for the maximum capacity and smallest verification scale interval for which the approval is sought.
- If so equipped, the "enhance resolution feature" of the device will be used during the tests. If this feature is not available, use the small weight method to determine the device errors before rounding.
- When the environmental chamber has reached the desire temperature, allow a minimum of 3 hours for the temperature of the DUT to stabilize.
The temperature of the DUT can be monitored by attaching a thermocouple with adhesive tape inside the DUT onto a component of relatively large mass. However, the thermocouple must not be attached to any live component(s) of the DUT. The temperature will be deemed to be stable when the temperature obtained from the thermocouple will have stabilized within ± 1°C. Once stabilized, the temperature obtained from the thermocouple will likely be different than the overall temperature of the environmental chamber. The requirement is only that the temperature of the DUT stabilizes to within ± 1°C.
- The test equipment such as load cell simulators, high precision reference indicators, must be isolated from the test conditions and maintained at constant ambient temperature and humidity.
- This test is performed following the series of temperature test described in LG-3.13. The first test
(≈ 20°C/50% RH) described below is in fact the last test in the series of temperature test. See the Recommended Test Sequence on page 3.3.
Procedure
At ≈ 20°C/50% RH
A. Condition the device. Record the temperature and humidity rate.
B. Perform a minimum of three increasing and decreasing load test and record the results.
At 40°C/85% RH
C. Increase the temperature of the chamber and raise the humidity rate.
D. Condition the device.
E. When the device has reached temperature and humidity stability, allow for 48 hours. The temperature and humidity rate must remain constant.
F. Then perform a minimum of three increasing and decreasing load tests. Record the results.
At 20°C/50% RH
G. Condition the device. Record the temperature and humidity rate.
H. Perform a minimum of three increasing and decreasing load test and record the results.
Interpretation of Results
Reference: Section 9, 10, 11 and 29 of the Specifications
The device meets the requirements if under the above conditions it perform within applicable limits of error.
For more details concerning the procedure, see OIML IR 76-1, annexe B.2.2, and IEC Publications 68-2-3 (1969) and 68-2-28 (1980)
LG-3.17 Electrostatic Discharge Test
Application
This test is intended for any complete electronic weighing devices and for any electronic major elements tested separately.
Settings and Procedure
For more details concerning the procedure, see OIML IR 76-1, annexe B.3.3, and IEC Publications series 801-2.
Note that the electrostatic discharge test is not presently performed by the Laboratory. MC intents to implement this test in the future.
LG-3.18 Short Time Power Reduction Test
Application
This test is intended for any complete electronic weighing devices and for any electronic major elements tested separately.
Settings and Procedure
For more details concerning the procedure, see OIML IR 76-1, annexe B.3.1.
Note that the short time power reduction test is not presently performed by the Laboratory. MC intents to implement this test in the future.
Application
This test is intended for any complete electronic weighing devices and for any electronic major elements tested separately.
Settings and Procedure
For more details concerning the procedure, see OIML IR 76-1, annexe B.3.2, and IEC Publications
series 801-4.
Note that the burst test is not presently performed by the Laboratory. MC intents to implement this test in the future.
LG-3.20 Endurance (Permanence) Test
Application
This test is intended for any complete mechanical or electronic weighing devices and for any weighing elements tested separately with capacities of up to 1000 kg (2000 lb). Devices are subjected to the repetitive loading and unloading of specific loads applied 100 000 times. The endurance test is performed after all other tests.
Settings
- AZSM may be in operation during the tests. It must be set to the lowest value; if zero is the lowest selectable value, it will be set to zero. The amount that the AZSM may track at once may not be set to a value larger than 0.6 d which is the maximum value allowed by the Specifications.
- f a device is provided with an IZSM, the test will be performed only once with the IZSM set at the upper limit of its range.
- The weighing device must be levelled to its reference position, be adjusted as close as possible to zero error, and pre-loaded to the maximum capacity at least once.
- The device must be set for the maximum capacity and smallest verification scale interval for which the approval is sought.
- If so equipped, the "enhance resolution feature" of the device will be used during the test. If this feature is not available, use the small weight method to determine the device errors before rounding.
- This test is performed at ambient temperature (≈ 20°C) or at the mid point of the temperature range if significantly different from 20°C.
- The following test load shall be used:
Devices with Max ≤100 kg: a load equal to 1/2 Max;
Devices with Max > 100 kg: a load between 1/4 and 1/2 of Max without exceeding 250 Kg.
Procedure
- After having moved the device to the permanence testing bench, perform an increasing and decreasing test, an eccentricity test, a load discrimination or sensitivity test, to ascertain that the device measures as close to zero error as possible. Recalibrate the DUT as necessary.
- Apply the test load 25 000 times; perform an increasing and decreasing load test and record the results.
- Apply the test load an additional 25 000 times; perform an increasing and decreasing load test and record the results.
- Apply the test load an additional 25 000 times; perform an increasing and decreasing load test and record the results.
- Apply the test load an additional 25 000 times.
- Perform a load discrimination test, an increasing and decreasing load test, an eccentricity test
- Record the results.
Interpretation of Results
Reference: Sections 9, 10, 11, 12, 13, 14, 15, 16, and 21 of the Specifications.
The device meets the requirements if all the results remains within the applicable limits of error.
Class III HD In-Service Limits of Error
Verification scale interval |
2 kg |
5 kg |
10kg |
20 kg |
In-Service LOE in Terms of Verification Scale Interval |
Load in kg |
Load in kg |
Load in kg |
Load in kg |
1 |
0 - 1000 |
0 - 2500 |
0 - 5000 |
0 - 10000 |
2 |
+1000 - 2600 |
+2500 - 6500 |
+5000 - 13000 |
+10000 - 26000 |
3 |
+2600 - 4200 |
+6500 - 10500 |
+13000 - 21000 |
+26000 - 42000 |
4 |
+4200 - 5800 |
+10500 - 14500 |
+21000 - 29000 |
+42000 - 58000 |
5 |
+5800 - 7400 |
+14500 - 18500 |
+29000 - 37000 |
+58000 - 74000 |
6 |
+7400 - 9000 |
+18500 - 22500 |
+37000 - 45000 |
+74000 - 90000 |
7 |
+9000 - 10600 |
+22500 - 26500 |
+45000 - 53000 |
+90000 - 106000 |
8 |
+10600 - 12200 |
+26500 - 30500 |
+53000 - 61000 |
+106000 - 122000 |
9 |
+12200 - 13800 |
+30500 - 34500 |
+61000 - 69000 |
+122000 - 138000 |
10 |
+13800 - 15400 |
+34500 - 38500 |
+69000 - 77000 |
+138000 - 154000 |
11 |
+15400 - 17000 |
+38500 - 42500 |
+77000 - 85000 |
+154000 - 170000 |
12 |
+17000 - 18600 |
+42500 - 46500 |
+85000 - 93000 |
+170000 - 186000 |
13 |
+18600 - 20200 |
+46500 - 50500 |
+93000 - 101000 |
+186000 - 202000 |
14 |
+20200 - 21800 |
+50500 - 54500 |
+101000 - 109000 |
+202000 - 218000 |
15 |
+21800 - 23400 |
+54500 - 58500 |
+109000 - 117000 |
+218000 - 234000 |
16 |
+23400 - 25000 |
+58500 - 62500 |
+117000 - 125000 |
+234000 - 250000 |
17 |
+25000 - 26600 |
+62500 - 66500 |
+125000 - 133000 |
+350000 - 266000 |
18 |
+26600 - 28200 |
+66500 - 70500 |
+133000 - 141000 |
+266000 - 282000 |
19 |
+28200 - 29800 |
+70500 - 74500 |
+141000 - 149000 |
+282000 - 298000 |
20 |
+29800 - 31400 |
+74500 - 78500 |
+149000 - 157000 |
+298000 - 314000 |
21 |
+31400 - 33000 |
+78500 - 82500 |
+157000 - 165000 |
+314000 - 330000 |
22 |
+ 33000 |
+82500 |
+165000 |
+330000 |
The following formula may be used to calculate in-service limits of error for class IIIHD devices:
| ( L / e - 500 ) | + 1 = | (Round the value up to the next whole number) |
| 800 | In-service limit of error in term of e |
L = Load or standard used to determine the LOE
e = the value of verification scale interval
The result is divided by 2 to find the acceptance LOE
Example:
In-service LOE for a known test load of 11 500 kg
e = 5 kg
11 500 kg ÷ 5 kg = 2 300
2 300 - 500 = 1 800
1 800 ÷ 800 = 2.25
2.25 + 1 = 3.25
3.25 rounded up = 4 e
Hence, the in-service LOE is 20 kg (4 X 5 kg)
The acceptance LOE is 10 kg
- Date modified:
