National Instruments 653 Series User Manual page 19

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Installation categories, also referred to as measurement categories, are defined in electrical safety standard IEC 61010-1.
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Working voltage is the highest rms value of an AC or DC voltage that can occur across any particular insulation.
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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.
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If you need to clean the product, use a soft, nonmetallic brush. Make sure
that the product is completely dry and free from contaminants before
returning 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 installation category
hardware label. Measurement circuits are subjected to working voltages
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
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MAINS voltage. This category is for measurements of voltages from
specially protected secondary circuits. Such voltage measurements
Chapter 1
1-11
Getting Started with Your NI 653X
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marked on the
NI 653X User Manual
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