National Instruments AT E Series User Manual
Page 19
Chapter 1
Introduction
© National Instruments Corporation
1-7
pollution degree stated in Appendix A,
. Pollution is foreign
matter in a solid, liquid, or gaseous state that can produce a reduction of
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, which becomes conductive due to
condensation.
Clean the product with a soft nonmetallic brush. The product 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 product is rated. Do not exceed the maximum ratings for the product.
Remove power from signal lines before connection to or disconnection
from the product.
Operate this product only at or below the installation category stated in
Appendix A,
.
The following is a description of installation categories:
•
Installation Category I is for measurements performed on circuits not
directly connected to MAINS
1
. This category is a signal level such as
voltages on a printed wire board (PWB) on the secondary of an
isolation transformer.
Examples of Installation Category I are measurements on circuits
not derived from MAINS and specially protected (internal)
MAINS-derived circuits.
•
Installation Category II is for measurements performed on circuits
directly connected to the low-voltage installation. This category refers
to local-level distribution such as that provided by a standard wall
outlet.
Examples of Installation Category II are measurements on household
appliances, portable tools, and similar equipment.
1
MAINS is defined as the electricity supply system to which the equipment concerned is designed to be connected either for
powering the equipment or for measurement purposes.