Laboratory manual for the evaluation of non-automatic weighing devices
Part 2, section 6—Agreement of registration
Table of contents
- 6.0 Agreement of registration – Generalities
Section 18 of the Specifications Relating to Non Automatic Weighing Devices (1998)
Schedule II of the Weights and Measures Act
6.0 Agreement of registration – Generalities
Devices may be calibrated in one unit and use internal calculations to convert from that unit to other units. All indications in different units must be in agreement with each other at all times. Conversion factors can be found in Schedule II of the Weights and Measures Act.
LG-6.01 Test for the agreement of registrations
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.
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.
- 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:
- Electronic digital values having the same value of verification scale interval must be in exact agreement;
- Analogue values having the same value of verification scale interval must agree within 0.25 times the value of the verification scale interval;
- 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 gross weights 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.
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.
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.
Weight classifier 10 kg × 5 g
The scale interval of the printing device is 10 g
Price ranges: 0 - 30 g (Included) = $1.00
Greater 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.
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
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.
To all DUT capable of indicating in a metric and in a non‑metric unit of registration.
- For each of the units of measurement in which the DUT is capable of registering, perform the two following steps.
- Set the DUT to register in the unit of measurement being verified.
- At least fourteen times, add a test load equal to e and each time, record the registration.
- Apply at load and record the indication in the unit the device was calibrated in. Use the "small weights" method to determine the true weight as indicated by the device. Remove the "small weights" once the true weight has been determined.
- Set the device to all other units it is capable of displaying and record the indication for each.
- Repeat steps 1 and 2 for 3 more loads, spread throughout the range of the device.
Interpretation of the results
The DUT is deemed to meet the requirements if:
- Part 1: for each unit of measurement tested, the registration did not skip any steps.
- Part 2: The device accurately converts the weight indication
| Applied load
| Internal metric reading
| Rounded to 0.05 kg
| Conversion to lb
| Indication in lb
Note: 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.
Note: 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).
Note: 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.
Note: 4 A device may display weight values in two units of measurement simultaneously.
Note: 5 All weight indications and registrations must be within tolerances.
- Rev. 1 (March 2010)
- Added second part to LG-6.02 to test for accuracy of conversion
- Formatting change
- Date modified: