Laboratories concerned with quantitative analyses require stringent calibration of scales. Modern scales are easily calibrated and the accuracy of scales is largely dependent on the accuracy of the calibration weight. Modern scales electronically divide the calibration weight to obtain all smaller readings and this requires a perfectly balanced electronic circuit. For most accurate requirements check scales with a calibration weight of similar weight as the specimens under evaluation. Other impinging issues are magnetic properties of the calibration weight and weights handling and storage.
Accuracy of calibration weights are defined from the grades of stainless steel as well as other contributing factors. These different grades have different magnetization/accuracy (eg 8.0g/cm3). Most calibration weights are available with certificates.
Calibration Weight Classes
Class E1 These weights are the highest accuracy class, and are intended to be used for traceability between national mass standards and OIML class E2 weights and lower. The maximum permissible error from nominal value at 1 kg is ±0.5 mg. Used as primary laboratory reference standard.
Class E2 Suitable for use for traceability of OIML class F1 weights and lower; also with OIML accuracy class I weighing instruments. The maximum permissible error from nominal value at 1 kg is ±1.6 mg. Used as a high precision standard for calibration of weights and special precision analytical instruments.
Class F1 Suitable for use for traceability of OIML class F2 weights and lower; also with OIML accuracy class I weighing instruments. The maximum permissible error from nominal value at 1 kg is ±5 mg. For the calibration of high accuracy class 2 balances.
Class F2 Suitable for use for traceability of OIML class M1 weights and lower; also with OIML accuracy class II weighing instruments. Intended for use in high value commercial transactions such as gold and precious stones. The maximum permissible error from nominal value at 1 kg is ±16 mg. Used as working standards for precision and analytical work, build-in weights, external weights to calibrate moderate precision balances.
Class M1 Suitable for use for traceability of OIML class M2 weights and lower; also with OIML accuracy class II weighing instruments. The maximum permissible error from nominal value at 1 kg is ±50 mg.
Class M2 Suitable for use for traceability of OIML class M3 weights; also with OIML accuracy class III weighing instruments. Intended for use in normal commercial transactions where goods are sold by weight. The maximum permissible error from nominal value at 1 kg is ±160 mg. Used for accuracy class III applications, industrial scales, dial scales, trip balances, platform scales
Class M3 Suitable for use with OIML accuracy class III or IIII weighing instruments. The maximum permissible error from nominal value at 1 kg is ±500 mg. May be used for accuracy class III L and IV.