Do all instruments in a factory have to be sent out for calibration?

Not necessarily. Enterprises can first classify their own management of measuring instruments, usually do the following classification: the first category (customarily referred to as Class A), the implementation of the state mandatory verification of measuring equipment, that is, "the organization's highest measurement standard instruments and instruments used for trade settlements, medical and health care, safety protection and environmental monitoring included in the mandatory verification directory of the work of the measuring instruments ". This type of measuring equipment should be implemented in accordance with national laws and regulations for mandatory verification. The second category (customarily referred to as Class B), enterprises for process monitoring, quality testing, internal accounting, business management and other aspects of measuring equipment. This type of measuring equipment can be used by the enterprise according to its purpose, frequency, use of environmental conditions, regulations, etc., to determine the calibration interval and implementation of calibration and confirmation. The third category (customarily referred to as Category C), the enterprise equipment installed on the monitoring instrumentation is not easy to dismantle (such as oil pressure gauges, pressure gauges), only play a role in indicating the instrumentation does not participate in the measurement (such as switchboard table) or no measurement characteristics of the test equipment (such as platforms, leveling instruments) and so on. This type of measuring equipment can be implemented by the enterprise one-time confirmation, without the need to implement subsequent verification and calibration. The fourth category, some equipment can be developed by the enterprise calibration method or the use of industry standards for their own calibration. This type of measuring equipment should be industry-specific equipment or the state does not have calibration regulations or calibration specifications of the experimental / test, measurement equipment.