The scope of compulsory verification of measuring instruments, including: the social utility measuring instruments; departments and enterprises, institutions, the use of the highest standard of measurement instruments; used for trade settlements, safety and security, medical and health care, environmental monitoring, etc., included in the "Chinese people's *** and the State of the mandatory verification of the work of measuring instruments detailed catalog" of the work of measuring instruments. Compulsory verification by the government administrative department in charge of measurement of mandatory implementation, the implementation of fixed-point periodic verification, the use of units do not have a choice. Non-compulsory verification of measuring instruments can be used by the unit's own legal management, the government measurement of the administrative departments focusing only on its legal management of the situation for supervision and inspection. Compulsory and non-compulsory calibration, are part of the legal system of calibration, is the measurement of measuring instruments according to law, the two forms of management, are subject to the constraints of the law.