Current Measuring Device - Baur PGK 25 Operating Instructions Manual

5. Guard Connection

Current measuring device

Operating mode A:
(test object connected to earth)
Operating mode B:
(test object not
connected to earth)
5-2
The current measuring device of the PGK 25 has 5 measuring
ranges from 1 µA to 10 mA. Due to the separately mounted
connectors for shield and current measuring terminal M, spurious
currents can be excluded from measurements.
With the operating mode switch (14) in position ''A'', the current
measuring terminal (15) is connected to earth. The current
measuring device acquires all currents which flow from the H.V.
output to earth. Internal insulation currents as well as corona
currents from test configuration are also acquired by the current
measurement. Through the shield connection, partial currents (e.g.
surface currents on insulators) can be returned to the high voltage
source, without being acquired by the current measuring device. If
the shield connection is not used it must be isolated from earth,
otherwise the µA-meter will be short-circuited.
With the operating mode switch (14) in position ''B'', the current
measuring terminal (15) is electrically isolated. The current
measuring device acquires all currents which are conducted
through the current measuring terminal (15). The insulation currents
and corona currents which flow from the instrument or the test
configuration to earth, will not be acquired by the current measuring
device. The shield connection may be connected to earth. The test
object must be configured in such a way, that it is insulate from
earth.
The test lead may not be interrupted during testing, otherwise
the test lead could carry high voltage!
Shield