M-18—Scales and point of sale (POS) systems incorporating proportional tare

Date: 2004-06-28
Bulletin: M-18 (rev. 2)
Category: Mass
Supercedes: M-18 (rev. 1)


Table of contents


1.0 Purpose

The purpose of this bulletin is to establish the policy relating to the approval and inspection of scales and Point of Sale (POS) systems incorporating proportional tare.

2.0 Scope

This bulletin is applicable to all scales or point of sale (POS) systems equipped with, or modified to include, proportional tare features.

3.0 Procedure

3.1 Proportional tare refers to a value of tare, automatically calculated by the scale or Electronic Cash Register (ECR), that is proportional to the gross weight of the product. It is derived from a percentage of the gross weight and is expressed in units of weight. In order to ensure the use of a single standard within the industry, the following formula shall be used when scales perform proportional tare:

% Tare = (Tare Weight ÷ Gross Weight) × 100

3.2 This percentage is then used to calculate the tare weight for a given gross weight of product, when the tare weight is proportional to the gross weight, and the actual value of the tare will be based on the amount of product sold (e.g. Individually wrapped confections).

4.0 Evaluation

4.1 New scales equipped with proportional tare capabilities, submitted to the Approval Services Laboratory for approval evaluation, shall be processed in the usual manner.

4.2 Previously approved scales that are modified by the manufacturer to include proportional tare features, shall be processed in the following manner:

4.2.1 The applicant shall write to the Approval Services Laboratory and provide the Notice of Approval number, the device model number and a description of the modification(s) to device functions.

4.2.2 The Laboratory shall coordinate field testing of at least one model of modified scale at a mutually acceptable location, such as the manufacturer's or dealer's premises or another convenient site.

4.2.3 Test data shall be forwarded to the Approval Services Laboratory and the existing Notice of Approval revised based on a successful evaluation.

4.3 When the software of an ECR includes proportional tare functions, the manufacturer, importer, or their representative shall contact their Regional Gravimetric Specialist prior to disposing of the ECR.

4.3.1 The Gravimetric Specialist will make arrangements to verify the proportional tare functions of each model of ECR. Fees and charges applicable to a request inspection shall apply.

4.4 Scales and ECRs already in use, that are modified to incorporate an approved or previously verified proportional tare function, shall not require an initial inspection. A report submitted to the nearest Measurement Canada District Office, as required by section 41 of the Weights and Measures Regulations will suffice.

4.5 In all cases, the procedures and criteria for evaluation will be those found in the Laboratory Manual for the Evaluation of Non-automatic Weighing Devices and/or the Field Inspection Manual - Non-automatic Weighing Devices.

5.0 Revision

The purpose of this revision is to:

  1. remove the reference to the individual telephone numbers
  2. add the correct brackets to the formula for determining percent tare; and
  3. add the references to the test procedures for evaluating this function.

The purpose of revision 1 was to:

  1. remove reference to the period of time during which priority was given to the approval evaluation of scales equipped with proportional tare.
  2. remove reference to a list of ECRs equipped with proportional tare.
  3. update the telephone numbers of the Regional Gravimetric Specialists; and
  4. make minor revisions to the text.
Date modified: