The International Organization of Legal Metrology (OIML) has established standards for the classification of calibration test weights. Varying from E0 & E1, which are the most accurate to M2 which are commonly used for calibrating platform scales, floor scales and other industrial weighing instruments.
As a rough guide we have listed desired accuracy against class below.
+/- 0.1% – UNclassed Proof Load Test Weights
+/- 0.05% – M3 (Check/calibrate coarse scales)
+/- 0.005% – M1 (Check/calibrate standard scales)
+/- 0.0015% – F2 (Check/calibrate portable balances)
+/- 0.0005% – F1 (Check/calibrate precision balances)
+/- 0.00015% – E2 (Check/calibrate analytical balances)
The choice of weight class depends on the intended use and the level of accuracy required for a particular application. If you’re unsure, talk to our team who can advise you on the right class for your equipment.