HT HT4010 User Manual page 26

The norm IEC/EN61010-1: Safety requirements for electrical
equipment for measurement, control and laboratory use, Part 1:
General requirements, defines what measuring category, usually
called overvoltage category, is. On § 6.7.4: Measuring circuits, it says:
(OMISSIS)
Circuits are divided into the following measurement categories:
•
Measurement category IV is for measurements performed at the
source of the low-voltage installation
Examples are electricity meters and measurements on primary
overcurrent protection devices and ripple control units
•
Measurement category III is for measurements performed in the
building installation
Examples are 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 and some other equipment, for example,
stationary motors
installation.
•
Measurement category II is for measurements performed on
circuits directly connected to the low voltage installation
Examples are measurements on household appliances, portable
tools and similar equipment.
•
Measurement category I is for measurements performed on
circuits not directly connected to MAINS
Examples are measurements on circuits not derived from MAINS,
and specially protected (internal) MAINS-derived circuits. In the
latter case, transient stresses are variable; for that reason, the
norm requires that the transient withstand capability of the
equipment is made known to the user
2. GENERAL DESCRIPTION
27
with permanent connection
HT4010
to fixed