1 generalization, generally, measuring instruments calibration cycle for one year, it can be. (This is set by the use of their own units, the independent inspection, that is, you do not check the national law is also no matter what you, but according to industry regulations, customer requirements, etc., to develop their own calibration cycle, self-test, or to send a test are available)
2 National mandatory calibration of measuring instruments, such as portable methane alarm, methane gas detection alarm, should be six months.
3 That is, in addition to the national mandatory verification of measuring instruments, the use of units to determine their own verification cycle.