AM-6
11
Measurement Categories
These definitions were derived from the international safety standard for
insulation coordination as it applies to measurement, control, and labora-
tory equipment. These measurement categories are explained in more detail
by the International Electrotechnical Commission; refer to either of their
publications: IEC 61010-1 or IEC 60664.
Measurement Category I
Signal level. Electronic and telecommunication equipment, or parts thereof.
Some examples include transient-protected electronic circuits inside photo-
copiers and modems.
Measurement Category II
Local level. Appliances, portable equipment, and the circuits they are plugged
into. Some examples include light fixtures, televisions, and long branch circuits.
Measurement Category III
Distribution level. Permanently installed machines and the circuits they are
hard-wired to. Some examples include conveyor systems and the main circuit
breaker panels of a building’s electrical system.
Measurement Category IV
Primary supply level. Overhead lines and other cable systems. Some examples
include cables, meters, transformers, and other exterior equipment owned by
the power utility.
