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Safety Notes
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CAT I
Secondary electrical circuits connected to an
AC electrical outlet through a transformer or
similar device.
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 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).
Measurement categories (Overvoltage categories)
This instrument complies with CAT II safety requirements.
To ensure safe operation of measurement instruments, IEC
61010 establishes safety standards for various electrical
environments, categorized as CAT I to CAT IV, and called
measurement categories. These are defined as follows.
Higher-numbered categories correspond to electrical
environments 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
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.
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.
