NI HDD-8266 Installation Guide
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© National Instruments
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Operate the hardware only at or below Pollution Degree 2. Pollution is foreign matter in a solid,
liquid, or gaseous state that can reduce dielectric strength or surface resistivity. The following is
a description of pollution degrees:
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Pollution Degree 1 means no pollution or only dry, nonconductive pollution occurs. The
pollution has no influence. Typical level for sealed components or coated PCBs.
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Pollution Degree 2 means that only nonconductive pollution occurs in most cases.
Occasionally, however, a temporary conductivity caused by condensation must be
expected. Typical level for most products.
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Pollution Degree 3 means that conductive pollution occurs, or dry, nonconductive pollution
occurs that becomes conductive due to condensation.
Operate the hardware at or below the measurement category
1
marked on the hardware label.
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
categories establish standard impulse withstand voltage levels that commonly occur in electrical
distribution systems. The following is a description of measurement categories:
•
Measurement Categories CAT I and CAT O (Other) are equivalent and are for
measurements performed on circuits not directly connected to the electrical distribution
system referred to as MAINS
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voltage. This category is for measurements of voltages from
specially protected secondary circuits. Such voltage measurements include signal levels,
special hardware, limited-energy parts of hardware, circuits powered by regulated
low-voltage sources, and electronics.
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Measurement Category II is for measurements performed on circuits directly connected to
MAINS. This category refers to local-level electrical distribution, such as that provided by
a standard wall outlet (for example, 115 AC voltage for U.S. or 230 AC voltage for Europe).
Examples of Measurement Category II are measurements performed on household
appliances, portable tools, and similar hardware.
•
Measurement Category III is for measurements performed in the building installation at the
distribution level. This category refers to measurements on hard-wired hardware such as
hardware 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 typically outside buildings. Examples include electricity meters and
measurements on primary overcurrent protection devices and on ripple control units.
To obtain the safety certification(s) for this product, visit
ni.com/certification
, search by
model number or product line, and click the appropriate link in the Certification column.
1
Measurement categories, also referred to as overvoltage or installation categories, are defined in electrical
safety standards IEC 61010-1 and IEC 60664-1.
2
Working voltage is the highest rms value of an AC or DC voltage that can occur across any particular
insulation.
3
MAINS is defined as a hazardous live electrical supply system that powers hardware. Suitably rated
measuring circuits may be connected to the MAINS for measuring purposes.
