Testboy TB-3000 Mode D'emploi page 36

Technical data
Measurement Category II
Measurements on the power circuits that have a direct plug connection to
the low voltage network. Normal short-circuit current < 10 kA.
This category refers to local-level electrical distribution, such as that
provided by a standard wall outlet (for example, 115 V AC voltage for U.S. or
230 V AC voltage for Europe). Examples of Measurement Category II are
measurements performed on household appliances, portable tools, and
similar modules.
Measurement Category III
Measurements within the building installation (stationary consumer devices
with non-plug-in connection, distributor connection, permanently installed
equipment in the distributor). Normal short-circuit current < 50 kA.
This category refers to measurements on hard-wired equipment in fixed
installations, distribution boards, and circuit breakers. Other examples are
wiring, including cables, bus bars, junction boxes, switches, socket outlets in
the fixed installation, and stationary motors with permanent connections to
fixed installations.
Measurement Category IV
Measurements at the source of the low voltage installation (meters, mains
connection, primary overcurrent protection). Normal short-circuit current >>
50 kA.
This category refers to measurements on primary over-current protection
devices and on ripple control units.
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Testboy TB-3000