Hioki 8910, Instruction Manual

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Safety Notes
6
Measurement categories
To ensure safe operation of measurement instruments, IEC 61010
establishes safety standards for various electrical environments,
categorized as CAT II to CAT IV, and called measurement categories.
These are defined as follows.
CAT II : Primary electrical circuits in equipment connected to an AC
electrical outlet by a power cord (portable tools, household
appliances, etc.)
CAT II covers directly measuring electrical outlet receptacles.
CAT III : Primary electrical circuits of heavy equipment (fixed
installations) connected directly to the distribution panel, and
feeders from the distribution panel to outlets.
CAT IV : The circuit from the service drop to the service entrance, and
to the power meter and primary overcurrent protection device
(distribution panel).
Using a measurement instrument in an environment designated with a
higher-numbered category than that for which the instrument is rated
could result in a severe accident, and must be carefully avoided.
Use of a measurement instrument that is not CAT-rated in CAT II to
CAT IV measurement applications could result in a severe accident,
and must be carefully avoided.