Compliance Information 6
1.2 IEC Measurement Category & Pollution Degree Denitions
Measurement Category (CAT) - classication of testing and measuring circuits according to the types
of mains circuits to which they are intended to be connected.
Measurement Category other than II, III, or IV : circuits that are not directly connected
to the mains supply.
Measurement Category II (CAT II) : test and measuring circuits connected directly to
utilization points (socket outlets and similar prints) of the low-voltage mains installation.
Measurement Category III (CAT III) : test and measuring circuits connected to the
distribution part of a building’s low-voltage mains installation.
Measurement Category IV (CAT IV) : test and measuring circuits connected at the
source of the building’s low-voltage mains installation.
Mains Isolated : is for measurements performed on circuits not directly connected to a
mains supply.
Pollution - addition of foreign matter, solid, liquid, or gaseous (ionized gases) that may produce a
reduction of dielectric strength or surface resistivity.
Pollution Degree 2 (P2) - only non-conductive pollution occurs except that occasionally a
temporary conductivity caused by condensation is expected
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