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© National Instruments Corporation 3 NI Smart Camera I/O Accessory User Guide
Operate the device 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:
• Pollution Degree 1 means no pollution or only dry, nonconductive pollution occurs. The pollution
has no influence.
• Pollution Degree 2 means that only nonconductive pollution occurs in most cases. Occasionally,
however, a temporary conductivity caused by condensation must be expected.
• Pollution Degree 3 means that conductive pollution occurs, or dry, nonconductive pollution occurs
that becomes conductive due to condensation.
You must insulate signal connections for the maximum voltage for which the device is rated. Do not
exceed the maximum ratings for the device. Do not install wiring while the device is live with electrical
signals. Do not remove or add connector blocks when power is connected to the system. Avoid contact
between your body and the connector block signal when hot swapping devices. Remove power from
signal lines before connecting them to or disconnecting them from the device.
Operate the device at or below the installation 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. Installation categories establish standard impulse
withstand voltage levels that commonly occur in electrical distribution systems. The following is a
description of installation categories:
• Installation Category I is for measurements performed on circuits not directly connected to the
electrical distribution system referred to as MAINS
3
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.
• Installation 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 (for example, 115 AC voltage for U.S. or 230 AC voltage for
Europe). Examples of Installation Category II are measurements performed on household
appliances, portable tools, and similar devices.
• Installation 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.
• Installation 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
Installation categories, also referred to as measurement categories, are 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
MAINS is defined as a hazardous live electrical supply system that powers equipment. Suitably rated measuring circuits may
be connected to the MAINS for measuring purposes.