What does CAT III, CAT IV mean?

QThere is an indication like "CAT III 600 V" on an electrical measuring instrument. What is the meaning?


To ensure the safe use of electrical measuring instruments, measurement categories are indicated.
In the EN61010 series of safety standards, the measurement is classified into measurement categories II to IV based on the rated voltage to ground and current capacity (the magnitude of current flowing in the event of a short circuit fault) of the measurement point and the transient overvoltage that occurs at the measurement point.
Please note that some products cannot be used depending on the measuring point.