Measuring instruments listed in the national mandatory calibration catalog must be sent for periodic inspection according to the required cycle. The rest, they arrange their own calibration cycle, regularly sent for inspection. In most cases, the cycle set one year.
Measuring instruments used in trade settlement, safety and security, health care, environmental monitoring are basically mandatory inspection. For example, your list of megohmmeter (shaking table)/various rulers/earth resistance tester/insulation resistance tester, etc. should be the category of strong inspection.
Isn't it the quality system certification ah? Hurry up to compile a weekly inspection plan.