Hioki 8847 - Overvoltage Categories (CAT)

Safety Information
5
This instrument complies with CAT II safety requirements. This instrument’s
input modules comply with CAT I or CAT II safety requirements. To ensure safe
operation of measurement instruments, IEC 60664 establishes safety standards
for various electrical environments, categorized as CAT I to CAT IV, and called
overvoltage categories. These are defined as follows.
CAT I Secondary electrical
circuits connected to
an AC electrical out-
let through a trans-
former or similar
device.
CAT II Primary electrical cir-
cuits in equipment
connected to an AC
electrical outlet by a power cord (portable tools, household appliances,
etc.) CAT II covers directly measuring electrical outlet receptacles.
CAT III Primary electrical circuits of heavy equipment (fixed installations) con-
nected 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).
Higher-numbered categories correspond to electrical environments with greater
momentary energy. So a measurement device designed for CAT III environ-
ments 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.
Overvoltage Categories (CAT)
The applicable measurement category is determined by the input module being
used. Refer to "17.6 Input Modules Specifications" ( p.304).