More about Weights
Weights are necessary for the following applications:
Calibration: To assess the performance of the balance or scale and prove traceability back to National and International standards. It is necessary to calibrate the instrument using a certified calibration weight.
Adjustment: It is possible that a balance or scale may stop weighing accurately. When this occurs it is necessary to correct this error by activating the adjustment routine on the instrument and then apply a certified calibration weight to perform the correction.
Balance Check: Balances and scales should be checked to ensure the calibration has not drifted and it is still weighing accurately. This is a routine process that should be carried out on a daily or before use basis.
This depends on how you will use the weights, and the specification of the balance or scale. However as a rule of thumb you can use the following:
Ultra Micro & Micro Balances Readability 0.0001mg & 0.001mg: Class E2
Semi–Micro Balances Readability 0.01mg: Class E2
Analytical Balances Readability 0.1mg: Class E2
Milligram Balances Readability 1mg Class F1
Top pan Balances Readability 0.01g Class F1
Top pan Balances Readability 0.1g Class F1
Top pan Balances / Scales Readability 1g (and less accurate) Class M1
Selecting Denomination / Test Points:
We recommend three test points across the operating range of the balance.
For example on a 200g x 0.1mg balance test points at: 200g, 100g and 100mg
Test points are not written is stone however and you can select test points specific to your application. For example if your most common weighing application on a 200g x 0.1mg is at 50g it makes sense to check the balance at this point rather than 100g
The validity of the weight used to check a balance is of critical importance, so we always recommend you use a UKAS certified weight.
We only offer UKAS certification through our own in-house metrology laboratory based in Oxford.
Having a UKAS certificate guarantees that correct calibration procedures have been followed and that traceability chains back to the international kg are documented and verified. Our ability to offer UKAS certification is independently audited by UKAS – United Kingdom Accreditation Service.
It is possible to purchase weights with “standard” or “ISO” certification. Providers offering this service have not been audited or approved by a third party, so there is no guarantee as to the validity of the certificate. Note even certification issued by an ISO9001 accredited company is not a guarantee of the validity of a certificate since the organisation is not audited specifically on their technical competence to perform the calibration or the traceability chains back to the International kg verified.
This very much depends on how you will use the weights, and the specification of the balance or scale. However as a rule of thumb you can use the following:
E2 Class Weights: Analytical Balances (0.1mg readability and more accurate).
F1 Class Weights: Milligram & Top Pan Balances (0.1g and more accurate).
M1 Class Weights: Compact Balances and Industrial Scales (1g and less accurate).
Again this depends on the application you are using the weight for, but for test purpose as described above.
We recommend a weight at approximately the capacity of the scale and again where you most typically weigh on the balance to perform the daily or before use check. To perform a monthly linearity check select 3 – 4 test points which cover the full range of the instrument.