How to Check a Weighing Balance or Scale
Why do you need carry out regular checks on your balance or scale?
It is important to perform regular checks on your weighing equipment using an external weight for two key reasons:
- To identify if calibration drift has occurred (calibration drift can occur for any number of reasons e.g. temperature changes, being moved, ageing electronics). This can be corrected by performing an adjustment.
- To identify if any other faults with the equipment have developed. For example a problem with the internal calibration feature.
Both of which could lead to inaccurate weighing results.
It is important to perform these checks in between service and calibration visits from your service provider.
When our engineers calibrates your equipment they will identify if calibration drift has occurred / developed any faults and correct where possible. However, what would happen if the error occurred some time after a service visit? The error would not be identified until the next service visit, leading to possibly many months of inaccurate weighing results.
For this reason it is important to carry out balance/scale checks in between routine service visits.
Selecting test points and weight denominations
In order to check the balance/scale effectively you will need to select several test points to ensure the equipment is performing correctly across it’s entire range.
We suggest two to three test points across the operating range of the balance. These test points also determine which denominations of weight you will require.
If necessary, multiple individual weights can be used together to meet the requirements of a test point.
|Example: a weighing balance with a capacity of 300g could have the below test points|
|Test Point||Weight Denomination|
|10g||1 x 10g|
|100g||1 x 100g|
|300g||1 x 100g and 1 x 200g|
Determining the correct weight class for your weighing balance or scale
We recommend using UKAS certified weights to perform checks, which quote a measurement of uncertainty. Weights are available in a number of different classes and the choice of class is dependant on the readability of your balance / scale. The table below suggests what class of weights you should use to test your weighing equipment.
|Equipment Specification||Recommended Class|
|Ultra Micro & Micro Balances||Readability 0.0001mg & 0.001mg||E2 Weights|
|Semi–Micro Balances||Readability 0.01mg||E2 Weights|
|Analytical Balances||Readability 0.1mg||E2 Weights|
|Milligram Balances||Readability 1mg||F1 Weights|
|Top pan Balances||Readability 0.01g||F1 Weights|
|Top pan Balances||Readability 0.1g||F1 Weights|
|Top pan Balances / Scales||Readability 1g (and less accurate)||M1 Weights|
For more information on choosing weights, please see our weight buying guide.
How do you perform a weighing balance or scale check?
The checking process is fairly straightforward:
- If equipped activate the internal calibration feature
- Apply the certified weight and note the displayed reading
- Compare the displayed reading against the measured value of the weight stated on the certificate and note the difference
- Determine if the difference meets your acceptance criteria
|Example: a 100g E2 Certified weight used to test a 200g x 0.1mg balance|
|Measured value of weight stated on certificate:||100.000 4 2g|
|Displayed reading on the balance:||100.000 1g|
How often should you check a weighing balance/scale?
UKAS (the United Kingdom Accreditation Service) recommend performing checks daily, or if you use the equipment less often before use.
In addition to performing the above checks you should ensure:
- Results are recorded in an appropriate log
- A procedure is documented which explains what happens if a balance fails a check. This will be dependant on the level of weighing expertise within your organisation. Please contact us for further advice.
- If a balance fails a check, a procedure is documented which explains how the balance is identified and isolated from use to prevent others using it.
- That any weights used to check the balance/scale are UKAS calibrated on a regular basis, to monitor drift and provide updated measured values that are required to perform the balance check. If you would would like to get a quote for UKAS weight calibration, please fill out this form.
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