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Notes on Safety
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Measurement categories
To ensure safe operation of measurement products,
IEC 61010 establishes safety standards for various
electrical environments, categorized as CAT II to
CAT IV, and called measurement categories.
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 product in an environment
designated with a higher-numbered category than
that for which the product 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.
