1, the stability of the equipment: not stable enough, easy to drift, easy to age the equipment, should be verified during the period.
2, the use of equipment and frequency: the frequent use of instruments and equipment; often disassembled, handling, carrying to the site to detect the instrumentation; the use of harsh environmental instruments and equipment, a high failure rate or once overloaded or suspected of quality problems of the instrumentation; service life of instruments and equipment nearing expiration of the period of verification should be carried out.
3, calibration data analysis: based on the analysis of the calibration data over the years, to determine whether the period of verification. Then what equipment can not be carried out during the verification? Generally good stability of the equipment, the use of low-frequency equipment, with a self-calibration function and each experiment before the self-calibration of the equipment, chemical analytical instruments each time with a standard sample to do, may not be considered for the period of verification.