D) Insulation Testing With Auxiliary Voltage - VOLTCRAFT ET-200 Bedienungsanleitung

If you cannot carry out a measurement, or if the continuity test fails (0 dis-
play), check the built-in fuse "FUSE". The fuse replacement is described in
the chapter "Cleaning and maintenance".
When you carry out a resistance measurement, make sure that the measuring points
you touch with the probe tips for measurement are free from dirt, oil, solder lacquer or
similar. An incorrect measurement may result under such circumstances.
In the low-ohm measurement, the resistance of the measuring leads is also
included in the measurement. The measuring lead resistance is approx. 0.5 Ω.
The equivalent circuit diagram is shown right. The two resistances "R E1"
and "R E2" represent the measuring leads. "R" corresponds to the measured
object. All three resistances are included in the measurement. To prevent the
measuring lead resistance from being included in the measurement, you can
activate the "ZERO" function.

d) Insulation testing with auxiliary voltage

Make sure that all the circuit parts, switches and system components and
other objects to be measured are disconnected from the voltage and dis-
charged at all times. If the meter detects a voltage ≥25 V/DC
or ≥25 V/AC in the measurement circuit, no insulation testing is possible.
Before every insulation test, carry out a voltage measurement (AC + DC).
During the insulation testing, dangerous voltages can be present at the probe
tips. A lightning symbol in the display warns of such a voltage. This voltage
is also present at all connected current circuits and leads. Do not touch any
switches or circuit parts during the insulation measurement.
Never grip beyond the tactile grip area marking of the probe tips or the
insulated alligator clips.
The insulation test enables the measurement of the insulation resistance of safety-related pro-
tective measures with an adjustable auxiliary voltage. Defective or insufficient insulation can
be detected in this way. The required insulation resistances can be found in the corresponding
standards.
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