Berner 313 Bedienungsanleitung Seite 28

The test instrument must only be used for the specified
measurement range.
According to the standard EN 61010-1 the following measure-
ment categories are defined:
Measurement Category CAT II
Measurements on circuits that are electrically connected di-
rectly to the network, via plugs in the home, office and labora-
tory.
Measurement Category CAT III
Measurements on the building installations: Fixed consumer
units, distributor connection, equipment fitted permanently to
the distributor.
Measurement Category CAT IV
Measurements at the source of the low voltage installation:
Meter, primary surge protection, main connection.
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