Toensuresafe operation ofmeasurementdevices,IEC 61010
establishes safety standards for various electrical environ-
ments, categorized as CAT II to CAT IV, and called measure-
ment categories.
CAT II: Primary electrical circuits in equipment connected to
anACelectricaloutlet by a power cord (portabletools,
household appliances, etc.)
CAT II covers directly measuring electrical outlet re-
ceptacles.
CAT III:Primary electrical circuits of heavy equipment (fixed
installations) connected directly to the distribution
panel, and feeders from the distribution panel to out-
lets.
CAT IV:The circuit from the service drop to the service en-
trance, and to the power meter and primary overcur-
rent protection device (distribution panel).
Using a measurement device in an environment designated
with a higher-numbered category than that for which the de-
vice 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.
Measurement categories
