# Laboratory manual for the evaluation of non-automatic weighing devices

## Part 2, section 7—Price computing feature

### Reference

Sections 19, 30 to 35, 46 and 47of the Specifications Relating to Non Automatic Weighing Devices (1998)

### 7.0 Price computing feature – Generalities

Devices used for direct sale can incorporate some cash register functionality, such as computing a total price for goods based on its weight and a pre determined unit price. All three of these values must always be in mathematical agreement with one another. In addition various requirements are described below to ensure clarity for all parties and to prevent the facilitation of fraud.

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/lb.

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.

7.4 A weighing system must not display or record any values when the correct calculated values exceed the display or printing capability. (An entry of 8 digits made into a defined field length of 7 digits will give an error indication).

Clarification: If a unit price of \$99.99/kg and a weight of 10.050 kg may be entered, then the total price display must have enough digits to display the extended price \$1 004.90 (at least 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-7.02.

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 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.

#### LG-7.01 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. All applicable tests are to be performed.

##### Procedure for price computing scales
• 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.
##### Procedure for scales 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.
##### Procedure for POS systems – Against a Price Lookup Code (PLU)
• Determine the keying sequence necessary to cause the device to compute a final price using a preprogrammed price lookup code (PLU).
• 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.
##### Procedure for POS systems – Against a manually scaled item
• Determine the keying sequence necessary to cause the device to read the scale, allow the operator to enter a price per unit (\$/kg) and if applicable a department code, and then 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‑7.02 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
• Apply several loads to the scale and enter different prices.
• 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.
• The following are suggested loads and unit prices:
Table 1: Suggested test loads and unit prices
Test # Net weight (kg) Unit price Total price Correct indication
A 0.01 \$4.54 \$0.045 40 \$0.05
B 0.01 \$4.55 \$0.045 50 \$0.05
C 0.01 \$4.90 \$0.049 00 \$0.05
D 0.01 \$5.10 \$0.051 00 \$0.05
E 0.01 \$2.50 \$0.025 00 \$0.02 or \$0.03
F 0.01 \$2.51 \$0.025 10 \$0.03
G 0.651 \$0.76 \$0.494 76 \$0.49
H 0.652 \$0.76 \$0.495 52 \$0.50
• Apply the following rounding rule:
Table 2: Rounding rules examples
Computed results Correct indication
0.020 0.02
0.021 0.02
0.022 0.02
0.023 0.02
0.024 0.02
0.025 0 0.02 or 0.03
0.025 1 0.03
##### 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).

### Revision

Original document

Date modified: