TS–023 Weighing instrument component replacement and hybrid conversions

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 – Weighing instrument component replacement

Load cell replacement

The certificate of approval issued for a weighing instrument will specify the make, model and number of load cell(s), which are to be used. 

For a different load cell(s) to be used in a weighing instrument, a variant to the certificate of approval must be submitted to Trading Standards, prior to the instrument being verified and used for trade. 

Note: When applying for a variant to an existing certificate of approval, to allow the use of a different type, make or model of load cell, evidence must be provided with the application confirming that the load cell has been tested and conforms to OIML R60. Supporting evidence includes an International Organisation of Legal Metrology (OIML) certificate issued by a test laboratory from an OIML issuing authority.   

Unless stated within the certificate of approval, a weighing instrument fitted with multiple load cells must have the same make, model, capacity, and specifications of load cell installed throughout the weighing instrument. 

For more information see the Applying for a type approval page on our website.

Applying for a type approval

Indicator replacement

Where an indicator is connected to a basework, the certificate of approval issued for a weighing instrument will specify the make and model of indicator that is to be used. However, it may also allow the use of an approved compatible indicator.

Note: A compatible indicator is one which: 

• Meets the compatibility criteria detailed in the certificate of approval for the weighing instrument, and 
• Has been issued with a certificate of approval by Trading Standards.   

Load cell marking 

Trading Standards requires the following instructions to be followed when an Accredited Person (AP) is completing verification or inspection test on a weighing instrument with a maximum capacity > 300 kilograms where load cells are difficult to access, and / or cannot be sighted for identification purposes, after installation:

• The weighing instrument is to be marked with the load cell details.  
• The load cell details are recorded in full on an adhesive label attached to the indicator housing or on a label that is in an easily visible location immediately adjacent to the indicator (see Figure 1 below).
• During a verification test, all individual load cells must be physically examined, and the load cell details sticker / label must be updated (see Figure 1 below).
• During an inspection or verification test, the load cell details on the label must be checked and recorded on the test sheet. For more information, please see TS–002 Information required on an Accredited Persons test sheet.

TS–002 Information required on an Accredited Persons test sheet

To facilitate the above requirements, the information required to be recorded on the label, in relation to the load cells, are:

• Make 
• Model
• Accuracy class
• Emax capacity
• Number of load cells
• Date of record 
• Personal identifier of accredited person.

Figure 1: An example of a label for recording load cell details on a weighing instrument

Note: The information must be clear, legible, and indelibly recorded.

Policy – Hybrid conversions

This policy also applies to hybrid type mechanical weighing instrument constructed with a load cell connected to mechanical lever work. There have been previous instances where hybrid conversions were permitted to be to be fitted with a load cell from another approved base work without a variant to the certificate of approval and/or compatibility calculations submitted to Trading Standards. In such cases, the below guidelines apply with respect to testing, stamping with a mark of verification and/or issuing a certificate of accuracy to a hybrid converted weighing instrument:

1. An accredited person is requested to issue a certificate of accuracy to a weighing instrument, which is stamped with a mark of verification issued by an Inspector of Weights and Measures (that is, stamped with a Crown)

• If the instrument meets the conditions of approval and passes all the required tests, issue a certificate of accuracy.
• If the instrument does not pass the tests, issue a Notice of Non-compliance.
• The mark of verification 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. Note: Approved components are specified within the certificate of approval.
• The instrument must then pass a verification test and must meet any requirements specified within the certificate of approval. If there is no certificate of approval, a type approval application form must be submitted to Trading Standards.

Applying for a type approval

2. An accredited person is requested to issue a certificate of accuracy to a weighing instrument, which is stamped with a mark of verification issued by an accredited person (that is, stamped with the personal identifier ‘APXX.XX’)

The equipment should only be tested if it has a certificate of approval and the instrument meets all conditions of approval:

• If the instrument meets the conditions of approval and passes all the required tests, issue a certificate of accuracy.

If there is no certificate of approval:

• Issue a Notice of Non-Compliance and advise the owner that the instrument must be issued with a certificate of approval before it can be used for trade.

3. The weighing instrument has just been converted to a hybrid type mechanical weighing instrument and is not stamped with a mark of verification

This requires a new certificate of approval to be issued by Trading Standards. The weighing instrument must only be fitted with an OIML R 60 approved load cell(s) and an indicator with a New Zealand certificate of approval. 

An approval application must be submitted to Trading Standards. The application must also include 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]  

Information for the process of applying for a type approval can be found here:

Applying for a type approval