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National Instruments Corporation
3
NI PCIe-8231 Quick Start Guide
Caution
National Instruments measurement products may be classified as either
Measurement Category I or II. Operate products at or below the Measurement Category
level specified in the hardware specifications.
Measurement Category
1
: Measurement circuits are subjected to working
voltages
2
and transient stresses (overvoltage) from the circuit to which they
are connected during measurement or test. Measurement Category
establishes standardized impulse withstand voltage levels that commonly
occur in electrical distribution systems. The following is a description of
Measurement (Installation
3
) Categories:
•
Measurement Category I is for measurements performed on circuits
not
directly connected to the electrical distribution system referred to
as MAINS
4
voltage. This category is for measurements of voltages
from specially protected secondary circuits. Such voltage
measurements include signal levels, special equipment, limited-energy
parts of equipment, circuits powered by regulated low-voltage sources,
and electronics.
•
Measurement Category II is for measurements performed on circuits
directly connected to the electrical distribution system. This category
refers to local-level electrical distribution, such as that provided by a
standard wall outlet (e.g., 115 V for U.S. or 230 V for Europe).
Examples of Measurement Category II are measurements performed
on household appliances, portable tools, and similar products.
•
Measurement Category III is for measurements performed in the
building installation at the distribution level. This category refers to
measurements on hard-wired equipment such as 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 is for measurements performed at the
primary electrical supply installation (<1,000 V). Examples include
electricity meters and measurements on primary overcurrent
protection devices and on ripple control units.
1
Measurement Categories as defined in electrical safety standard IEC 61010-1.
2
Working voltage is the highest rms value of an AC or DC voltage that can occur across any particular insulation.
3
Measurement Category is also referred to as Installation Category.
4
MAINS is defined as the (hazardous live) electrical supply system to which equipment is designed to be connected for the
purpose of powering the equipment. Suitably rated measuring circuits may be connected to the MAINS for measuring
purposes.
