© National Instruments
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1-3
Do
not
operate the product in an explosive atmosphere or where there may be flammable gases
or fumes. If you must operate the product in such an environment, it must be in a suitably rated
enclosure.
If you need to clean the product, use a soft, nonmetallic brush. The product
must
be completely
dry and free from contaminants before you return it to service.
Operate the product 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 product is rated.
Do
not
exceed the maximum ratings for the product. Do not install wiring while the product 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
modules. Remove power from signal lines before connecting them to or disconnecting them
from the product.
Operate the product 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 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 hardware, limited-energy parts of hardware,
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 (MAINS
3
). This category refers to local-level electrical
distribution, such as that provided by a standard wall outlet (for example, 115 AC voltage
1
Measurement categories, also referred to as overvoltage or installation categories, are defined in electrical
safety standard 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.
