TS–023 Suitability of using a load cell and hybrid conversions on weighing instruments

Reference documents

• OIML R76 - Non-automatic weighing instruments: Part 1 Metrological and technical requirements – Tests [PDF, 1.44 MB](external link)
• OIML R60 – Metrological regulation for load cells: Part 1 Metrological and technical requirements [PDF, 4.27 MB](external link)
• Certificate of Approval Register

Policy

The Certificate of Approval issued for a weighing instrument details the particular type of load cell(s) and the type of indicator. The weighing instrument must only use the type of load cell(s) specified in the Certificate of Approval.

To use a different load cell(s) requires a variant to the Certificate of Approval unless the certificate allows the use of an alternative OIML R 60 approved load cell(s).

This policy also applies to hybrid type mechanical weighing instrument constructed with a load cell and lever work. However, there have been previous instances where hybrid conversions were permitted to be to be fitted with a load cell from other approved base works without a proper variant and/or compatibility calculations. In such cases, the below guidelines apply with respect to applying a MOV and/or issuing a COA to a hybrid converted weighing instruments:

1. AP requested to issue a COA for a weighing Instrument with an MOV applied by an Inspector of Weights and Measures

• Continue to issue a COA, if the instrument passes all required tests.
• If the instrument does not pass test, issue a Notice of Non-compliance.
• The MOV is only valid until the instrument fails the inspection test. If any of the components are repaired or replaced, any such repair or replacement must be done using approved components.
• The instrument must then go through a verification test and must meet the approval certificate requirements. If there is no approval certificate, an approval application must be lodged with Trading Standards.

2. AP requested to issue a COA for a weighing instrument that is marked with a MOV by an AP

The equipment may only be stamped if it has Certificate of Approval issued in respect of it and the instrument meets the conditions of approval.

• Issue a COA if it complies with the inspection test, and any conditions of approval
• If there is no Certificate of Approval, issue a Notice of Non-compliance, and advise the owner of the instrument to submit an application for approval to Trading Standards

3. Instrument under test requires Verification as a new conversion

Trading Standards would treat it as a new approval, use OIML R 60 approved load cell and approved indicator. An approval application must be submitted to Trading Standards.

Compatibility calculations to determine the suitability of load cell(s) and indicator in a weighing instrument

The following excel document can be used to assess compatibility:

Compatibility template [XLSX, 56 KB]