What Class Of Weight Do You Need?

What weights do you need to check or calibrate a Balance or Weighing Scale?

OIML are an international standards setting body for legal metrology and set the standards and tolerances for weights, weighing equipment, balances and weighing scales. Calibrated test weights come in a number of different classes such as M3, M2, M1, F2, F1, E2, E1 and E0 M3 being the least accurate and E0 being the most. In the U.K. the Trading Standards Departments of Councils also issue Stamped Weights that are used when selling products to the public by weight. E0 weights would only be used as a master calibration standard held by a calibration laboratory for the calibration of other weights. Generally a class greater than the ones being calibrated are use so E0 calibrates E1 and E1 calibrates E2 etc.

What class of weight do you need?

It's imperative you use the correct class of weight to calibrate your Balance or Weighing Scales, otherwise you will not get accurate results from your weighing scales or balances. AML are always on hand if you require some advice and we also supply a range of calibrated test weights to OIML tolerances and standards. AML are UKAS accredited for the calibration of weigh scales and weigh balances so you can be assured of the correct advice from us. We are here to help! Below is the suggested class of weight for a particular capacity of balance or weighing scale.
Scale capacity 1kg 100g 10g 1g 100mg 10mg 1mg 0.1mg 0.01mg
Up to 200g F2 F1 E2
200g – 1kg F2 F1 F1/E2
1kg – 30kg M1 M1 M1 F2 F1
30kg – 100kg M1 M1 M1
over 100kg M1 M1 M1

How to Handle Calibrated Test Weights?

Great care must be taken when handling weights that are of a greater class than M1 weight tolerance, you must always use tweezers / weight handlers and or white cotton gloves. When placing the weight on the balance pan a small piece of tissue should be put down to protect the weight from contamination. For larger cast iron OIML M1 weights cardboard should be placed on to of the weigh pan. E2 and E1 weights are particularly susceptible to contamination and the greatest of care must be taken when using these high accuracy weights.

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