Operation Manual

48 GMC-I Messtechnik GmbH
Measurements R
SL
– MΩ
ISO
@10 V/100 V – CAP Switch positions (a-b) (a-E) (b-E)
Auto-ranging is active during insulation resistance measurement.
If the measured value is less than 10% of the measuring range
after manual measuring range selection (see chapter 4.1.2), u r
(under-range) appears at the display. You should then select the
next smaller measuring range with the help of the
 key.
Automatic Recognition of Interference Voltage During
Insulation Resistance Measurement (only in AUTORANGE Mode)
If, during insulation measurement, the instrument detects an
interference voltage of greater than 15 V AC or 25 V DC (assuming: U
in-
terference
≠ U
ISO
, Riq < 100 kΩ), „Error“ is briefly displayed at the
LCD. The instrument is then automatically switched to voltage
measurement, and the currently measured voltage value is dis-
played.
Note
A polarity-dependent dead zone results in erroneous mea-
surements for automatic interference voltage detection. The
dead zone lies within a range of 60 to 135 V DC AC
TRMS
sinusoidal (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 MΩ
ISO
measurement can be started by once again pressing the
UISO ON / OFF key.
If a voltage of greater than 110 V DC AC is present, it is indicated by
means of an acoustic signal, as well as optically with the “UHI”
symbol at the display.
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 conductors
a-b, a-E and b-E. Repeat the measurement.
6.3.4 Ending the Measurement and Discharging
Ð Briefly press the UISO ON / OFF key.
After measurement has been completed, any remaining residual
voltage is displayed which may result from cable capacitance.
The instrument’s internal 120 kΩ 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 below 25 V!
Note
The instrument’s batteries are rapidly depleted during insulation
resistance measurement. Deactivate insulation resistance mea-
surement between measurements for this reason. Use only
alkaline manganese batteries in accordance with IEC 6 LR61.
Note
Rotary selector switch positions a-b, a-E and b-E are
intended solely for the detection of interference voltage up to
110 V during insulation resistance measurement.
Voltage measurement may only be performed with the rotary
selector switch set to the V , V or the V position.
The DATA, MIN/MAX and ZERO functions are not available
in this case.