Instrument calibration can usually be divided into the following five methods according to different management links:

1. Periodic calibration, that is, regular calibration of measuring instruments that have been used for a period of time;

2. Factory calibration, that is, calibration performed by enterprises and institutions that manufacture measuring instruments before sales;

3. Post-repair calibration, that is, calibration of repaired measuring instruments before delivery for use;

4. Import calibration, that is, calibration of imported measuring instruments by relevant government metrology administrative departments after customs clearance;

5. Arbitration calibration, that is, calibration for the purpose of arbitration. Measuring instruments can be divided into mandatory calibration and non-mandatory calibration according to the nature of management, and the two are collectively referred to as metrology legal calibration.