3
――――――――――――――――――――――――――――――――――――――
――――――――――――――――――――――――――――――――――
Measurement categories (Overvoltage categories)
This device conforms to the safety requirements for CAT II
(600V), CAT III (300V) measurement instruments.
To ensure safe operation of measurement devices, 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.
CAT I : Secondary electrical circuits that are connected to a wall
outlet through a transformer or similar instrument.
CAT II : Primary electrical circuits in equipment connected to a
wall outlet via a power cord (portable tools, household
appliances, etc.)
CAT III : Primary electrical circuits of heavy equip ment (fixed
installations) connected directly to the distribution
panel, and feeders between the distribution panel and
outlets.
CAT IV : The circuit from the service drop to the service entrance,
then to the power meter and to the primary overcurrent
protection instrument.
Higher-numbered categories correspond to electrical environments
with greater momentary energy. So a measurement device
designed for CAT III environments can endure greater momentary
energythanadevicedesignedforCATII.
Using a measurement device in an environment designated with a
higher-numbered category than that for which the device is rated
could result in a severe accident, and must be carefully avoided.
Never use a CAT I measuring device in CAT II, III, or IV
environments.
The measurement categories comply with the Overvoltage
Categories of the IEC60664 Standards.