Getting Started with the NI 17xx
20
ni.com
•
Pollution Degree 3—Conductive pollution or dry,
nonconductive pollution occurs. Nonconductive pollution
becomes conductive because of condensation.
Clean the device and accessories by brushing off light dust with a
soft, nonmetallic brush. Remove other contaminants with a stiff,
nonmetallic brush. The unit
must
be completely dry and free from
contaminants before returning it to service.
You
must
insulate signal connections for the maximum voltage for
which the device is rated. Do
not
exceed the maximum ratings for
the device. Remove power from signal lines before connection to
or disconnection from the device.
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 (Installation
3
) Category establishes standardized
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
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
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.
