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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 I 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.
