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July 2017 - Verification Method For Weighing Instruments

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VERIFICATION METHOD FOR WEIGHING INSTRUMENTS AS PRESCRIBED IN SANS 1649 OF 2014


The manner in which weighing instruments that are used for trade purposes need to be verified is clearly prescribed. We urge end users to ensure that their verification service provider is verifying accordingly.  

Below are some key questions that you should be asking when your weighing instruments are being tested.
1. Is my verifier using the correct capacity of standard weights?
The Verifier needs to take 50% standard weights of the maximum capacity of the instrument being verified to site. When testing weighing instruments of 1 Ton and less, 100% of full complement of standard weights needs to be used. If your weighbridge has a capacity of 60 Ton the verifiers needs to have 30 ton standard weights on site.

2. Is my verifier bringing less than the 50% standard weights to site and using the repeatability method?
The verifier may use one third of the standard weights maximum capacity if the repeatability error is not greater than 0,3e. Whether or not the weighing instrument will meet the requirements of the repeatability test can only be determined when the verifier is on site, therefore 50% standard weights should be supplied in case of  the weighing instrument not meeting the repeatability requirements.
A Sasco Weighbridge Test Unit with 30 ton Standard Weights inherently reduces make-up weight required.
3. Are my weighing instruments being tested to full maximum capacity?
As part of the accuracy of weighing it is a requirement to test an instrument to maximum capacity.  This means that if your weighbridge is 60 ton then at some point in the test there should be 60 ton of weight on the weighbridge.  The 60 ton can be made up as follows: 30 ton standard weights and 30 ton make-up weight.  In the case of a repeatability test there will be 20 ton of standard weights and 40 ton of make-up weight.

4. Is it a new installation and is this the initial verification test?
In the case of a new weighing instrument, the initial verification test is required to be tested with 50% standard weights of maximum capacity.

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