User Manual
GMC-I Messtechnik GmbH 41
Measurements: V/Hz, , , Temp (°C/°F), , M
@UISO
, A/Hz
Automatic Recognition of Interference Voltage
during Insulation Resistance Measurement
If the instrument detects interference voltage of greater than
15 V AC or > 25 V DC during insulation testing (condition: U
interference
U
ISO
, e.g. Riq < 100 k at 100 V, see Seite 58, footnote 1),
Error is briefly displayed at the LCD. The instrument is then
automatically switched to voltage measurement, and the currently
measured voltage value is displayed.
Note
A dead zone results in erroneous measurements for
automatic interference voltage detection during insulation
resistance measurement. The dead zone lies within a range
of 80% to 120% of the selected test voltage
(in the case of an interference voltage whose value is equal
to that of measuring voltage, the two voltages neutralize
each other).
Manual switching to insulation resistance measurement is
disabled for as long as voltage is applied to the test terminals.
If interference voltage is no longer present, the M
@ISO
measurement can be started by once again pressing the
U
ISO ON / OFF key.
Attention!
!
If Error appears at the display, the cable (the device under
test) is most likely capacitively charged to a
significant extent.
Remedy:
Short circuit the cable (the device under test). Repeat the
measurement.
5.7.3 Ending the Measurement and Discharging
➭ Briefly press the U
ISO ON / OFF key.
After measurement has been completed, any remaining residual
voltage is displayed which may result from cable capacitance.
The instrument’s internal 100 M resistor causes rapid
discharging. However, contact to the device under test must be
maintained. The falling voltage value can be observed directly at
the LCD. Do not disconnect the device under test until the voltage value
has dropped to < 25 V!
Note
The instrument’s batteries are rapidly depleted during
insulation resistance measurement. Deactivate insulation
resistance measurement between measurements for this
reason. Use only alkaline manganese batteries in
accordance with IEC 6 LR61.
Note
Rotary selector switch position “V1
M
/
M
@UISO
” is
available for the detection of interference voltage during
insulation resistance measurement.
Use switch position V , V or V in order to perform
precise voltage measurements.
+
–
0V !
Discharge
025
.
0
UISO
V
DC
AC
TRMS
ISO 500 V