Chapter 2 Installing the Hardware and Software
© National Instruments Corporation 2-3 FP-2000/2010/2015 User Manual
voltages on a printed wiring board (PWB) on the secondary of an
isolation transformer.
Examples of Installation Category I are measurements on circuits not
derived from MAINS and specially protected (internal)
MAINS-derived circuits.
• Installation Category II is for measurements performed on circuits
directly connected to the low-voltage installation. This category refers
to local-level distribution, such as that provided by a standard wall
outlet.
Examples of Installation Category II are measurements on household
appliances, portable tools, and similar equipment.
• Installation Category III is for measurements performed in the building
installation. This category is a distribution level, referring to
hard-wired equipment that does not rely on standard building
insulation.
Examples of Installation Category III include measurements on
distribution circuits and circuit-breakers. Other examples of
Installation Category III are wiring including cables, bus-bars, junction
boxes, switches, socket-outlets in the building/fixed installation, and
equipment for industrial use, such as stationary motors with a
permanent connection to the building/fixed installation.
• Installation Category IV is for measurements performed at the source
of the low-voltage (< 1,000 V) installation.
Examples of Installation Category IV are electric meters, and
measurements on primary overcurrent protection devices and
ripple-control units.
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