User manual

DO189-1

TA133-User’s Guide

IEC Measurement Categories

Definitions and Examples (Clause 6.5.2)

Measurement Category I Definition: Measurement category I is for measurements performed

on circuits not directly connected to a mains supply.

Examples: Measurements in circuits not derived from a mains supply

and specially protected ( internal ) circuits derived

from a mains supply. In the latter case, transient stresses

are variable; for that reason it is required that the

transient withstand capability of the equipment is made

known to the user.

Measurement Category II Definition: Measurement category II is for measurements performed

CAT II on circuits directly connected to the low voltage

installation.

Examples: Household appliances, portable tools and similar

equipment.

Measurement Category III Definition: Measurement category III is for measurements

CAT III performed in the building installation.

Examples: Measurements on distribution boards, circuit breakers,

wiring including cables, bus-bars, junction boxes, switches,

socket-outlets in the fixed installation and equipment for

industrial use like for example stationary motors with per-

manent connection to the fixed installation.

Measurement Category IV Definition: Measurement category IV is for measurements

CAT IV performed at the source of the low-voltage installation.

Examples: Electricity meters and measurements on primary over

current protection devices and and ripple control units.