
Measurement categories (Overvoltage categories)
This product conforms to the safety requirements
for CAT I measurement products.
To ensure safe operation of measurement prod-
ucts, IEC 61010 establishes safety standards for
various electrical environments, categorized as
CAT I to CAT IV, and called measurement catego-
ries. These are defined as follows.
Higher-numbered categories correspond to electri-
cal environments with greater momentary energy,
so a measurement product designed for CAT III
environments can endure greater momentary
energy than one designed for CAT II. Using a mea-
surement product in an environment designated
with a higher-numbered category than that for
which the product is rated could result in a severe
accident, and must be carefully avoided.
Never use a CAT I measuring product in CAT II, III,
or IV environments.
The measurement categories comply with the
Overvoltage Categories of the IEC60664 Stan-
dards.
CAT I Secondary electrical circuits connected to an AC electri-
cal 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 in-
stallations) 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 protec-
tion device (distribution panel).