Verifying weighing instruments for trade

For a weighing instrument to be suitable for trade use, the National Measurement Act 1960 states it must:

• operate within the limits of error permitted under the regulations
• be pattern approved.

Certificates of approval

We issue certificates of approval for pattern approved instruments under these categories:

• 6 - weighing instruments
• 7 - counting instruments (obsolete, now category 6/4C) 
• 6B - conversion of weighing Instruments
• 6/10B - electronic weighbridges self-indicating

Advertising labels

You can apply a label advertising your business on the measuring instruments you verify. You must, however, ensure it cannot be confused with a verification mark or you may be in breach of the Act. We suggest adding 'this is not a verification mark' to your label to avoid confusion.

Find out more about placing verification labels on the verifying instruments for trade page.

Alternative load receptors

You may need to verify a non-automatic weighing instrument (NAWI) with a load receptor different to its certificate of approval. A manufacturer may have supplied the alternative load receptor or the business modified the original to suit their needs. Modifications can include adding scoops or rollers to the original or replacing the load receptor with a different type.

We still consider a NAWI with a modified load receptor, an approved pattern if:

• the modification does not affect the instrument’s measurement performance
• it meets all requirements under its NITP including accuracy, repeatability and eccentricity
• you can complete the NITP tests, including the eccentricity test 
• the load receptor is stable and is not tilted during loading or weighing
• the load receptor meets the requirements of its certificate of approval when it transmits the weight of the load to the load-measuring device 
• the alternative load receptor’s weight plus the weighing instrument’s maximum capacity doesn’t exceed the load cells’ capacity
• the weight of the alternative load receptor is within the instrument’s initial zero setting range
• modifications not part of the alternative load receptor don’t overhang the load receptor, e.g. rollers to facilitate loading
• removable load receptors that are not symmetrically loaded are only located in a single orientation. The modification mustn’t cause excessive eccentric loading of the weighing instrument:
  • the centre of gravity for the modification must be located approximately in the centre of the load receptor
  • no part of the modification shall overhang the area of the original load receptor
• the instrument is re-verified after the modification.

Re-verification as a result of adjustment or repair

You may need to verify a weighing instrument after it has been adjusted or repaired. This depends on whether the non-compliance issue could affect its metrological performance.

When not to re-verify

Don’t re-verify if a trade measurement inspector has marked it non-compliant because of:

• environmental parameters outside those permitted in the certificate of approval
• faulty auxiliary indicating or printing device
• faulty keypad buttons
• faulty LCD displays (missing segments)
• incomplete details on instrument display (missing decals)
• incorrect, incomplete, illegible or missing data plate
• unstable installation, instrument not securely fixed
• faulty level bubble
• faulty zero indicating device
• missing or broken levelling feet
• non-compliant weighbridge approaches.

After repair, the trader can use the instrument for trade. 

When to re-verify

You will need to re-verify if the non-compliance issues include:

• faults in electronic circuit boards
• faulty LCD displays (unreadable)
• use of incorrect software version
• price computing errors
• accuracy, eccentricity and repeatability errors in excess of the maximum permission errors (MPE)
• accuracy of zero and tare setting
• exceeds permitted discrimination or sensitivity
• faulty zeroing device
• zero shift in excess of MPE
• belt weighers and automatic totalising hopper weighers operating outside flow rate range.

Ensure you remove or obliterate the previous verification mark. After any adjustment or repair, you can re-verify the instrument.

Keeping non-automatic weighing instruments level

Non-automatic weighing instruments must be level when you conduct a test for verification.

If the level bubble is not clearly visible to the user, you must affix a notice indicating where it is on the instrument.

Explain to the trader that if an instrument is not level and giving inaccurate measurements, it may be an offence under the Act. They must also ensure their staff know how to check whether their instruments are staying level.

Direct them to weighbridges used for trade to find out more.

Weighing instrument conversion

The general certificate 6B/0: conversion of weighing instruments allows you to submit a conversion certificate for your NAWI. The general certificate has calculations to determine if the components used to convert or manufacture an instrument are suitable. 

To submit a conversion certificate for an instrument (except a full load cell) with a capacity over 100 kg, you can only:

• replace an indicator on a full load cell (other than single load cell instruments), lever or load cell NAWI
• convert a mechanical indicating weighing instrument (other than an overhead track weighing instruments) to a lever or load cell instrument
• replace the load cell on a lever load cell weighing instrument to retain the instrument as a lever or load cell instrument.

When verifying, you must be mark these instruments with the conversion number (i.e. 6B/XXX).

Weighbridge platforms are touching each other

Adjacent platforms on a multi-platform weighbridge can come into contact with each other as vehicles move on and off the weighbridge. This is usually due to the design or installation of the platforms.

Although contact may be minimal, the adjacent platform may temporarily display an indication other than zero with no load. The temporary display of a load other than zero is acceptable while a vehicle is moving over the multi-platform weighbridge.

When a vehicle is stationary and the indicators are stable, the indicated weight must reflect the applied load within the applicable MPE (zero or otherwise).

Weighbridges installed without a pit

Weighbridges without a pit must have:

• a clearance under the lowest live part of the platforms of at least 150 mm
• a floor between load cell supports that is:
• composed of concrete at least 75 mm thick
• effectively drained
• kept free from any accumulation of water, mud or debris.

If a weighbridge does not comply, the trader must either:

• rectify the weighbridge installation to comply with these requirements
• seek permission by emailing the manager licensing and appointments at tmlicensees@measurement.gov.au to deviate from the requirements. This request must include:
  • weighbridge details:
    • location
    • capacity
    • serial number
  • photographs of the installation
  • details of a risk assessment as to how they will ensure the floor under the weighbridge will be:
    • effectively drained
    • kept free from any accumulation of water, mud or debris.