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Safety Notes
4
The 3144-20 NOISE SEARCH TESTER complies with CAT I
safety requirements.
The 9741 CLAMP ON VOLTAGE SENSOR complies with
CAT III 200 V safety requirements.
To ensure safe operation of measurement instruments, IEC
61010 establishes safety standards for various electrical en-
vironments, categorized as CAT I to CAT IV, and called mea-
surement categories. These are defined as follows.
CAT I Secondary electrical circuits connected to an AC
electrical outlet through a transformer or similar de-
vice.
CAT II Primary electrical circuits in equipment connected to
an AC electrical outlet by a power cord (portable
tools, household appliances, etc.)
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).
Higher-numbered categories correspond to electrical environ-
ments with greater momentary energy. So a measurement
device designed for CAT III environments can endure greater
momentary energy than a device designed for CAT II.
Using a measurement instrument in an environment designat-
ed with a higher-numbered category than that for which the in-
strument is rated could result in a severe accident, and must
be carefully avoided.
Never use a CAT I measuring instrument in CAT II, III, or IV
environments.
The measurement categories comply with the Overvoltage
Categories of the IEC60664 Standards.
Measurement categories (Overvoltage categories)