Operation Manual
4 GMC-I Messtechnik GmbH
3 Performing Measurements
3.1 Switching the Instrument On and Off, Energy-Saving
Mode, Automatic Shutdown
The instrument is switched on by pressing and holding the START
key. Briefly press the START key twice in order to switch the instru-
ment off, during which no voltage may be applied to the test
probes! The instrument is switched to the standby mode after
several seconds (reduced brightness), if none of the keys has
been pressed and no voltage is applied to the test probes. The
instrument is switched out of the standby mode (i.e. back to full
brightness) by pressing any key or applying voltage to the test
probes. The instrument is shutdown automatically if it has
remained inactive for about 1 minute, i.e. if no keys have been
pressed and no voltage has been applied to the test probes dur-
ing this time.
3.2 Instructions and Principles with Validity for
All Measurements
• The desired functions or parameters are selected with the
R
ISO/USPD, FUNC, UTEST ▲ and UTEST ▼ keys. Measurement is
triggered by pressing the START key. All selected functions or
parameters remain valid until they are changed.
• If (interference) voltage of greater than 10 V is applied to the
test probes, this is indicated at the display in the UIN field
along with the measured value, as well as the “!” symbol. If
this is the case, the START key is disabled.
Bild 3.1 (Interference) Voltage Display
• If battery voltage is too low (only the red field is lit up in the
battery symbol), measurement cannot be started. After press-
ing the START key, the depleted battery symbol appears for
about 1 second (see figure below). Replace the batteries as
described in section 5.1 on page 7.
➭ When measuring high insulation resistance, the measurement
cables should be laid unobstructed in the room, or placed
upon a material with good insulating properties.
➭ Contact the device under test with the test probe before trig-
gering measurement with the START key, thus causing any
possible interference voltage to appear at the display.
➭ Do not remove the test probes prematurely during the course
of the measurement, because this may lead to distorted mea-
surement results.
After insulation measurement has been completed, any remaining
residual voltage is displayed as U
IN , which may result from cable
capacitance. Contact to the device under test must be main-
tained for as long as a capacitive DUT is being discharged via the
test instrument’s internal resistor. The falling voltage value can be
observed directly at the U
IN display. Do not disconnect the DUT
until voltage U
IN is less than 25 V!
3.3 Measuring Functions
Attention!
• Each time before measuring insulation resistance or surge
protection, make sure that the device under test is voltage-
free!
• Do not touch the device under test or the test probes during
measurement, and for a short time thereafter as long the DUT
is being discharged.
• The DUT may be charged with as much as 1000 V during
measurement, for which reason contact to the DUT must be
maintained after measurement has been completed until it is
fully discharged! Residual voltage appears at the display along
with the “!” warning symbol.
• Do not remove the test probes until voltage has dropped to a
safe level and the “!” warning symbol has been cleared from
the display.
• All consuming devices must be disconnected and the
switches must be turned on when measuring insulation resis-
tance between conductors.
3.3.1 Voltage Measurement
➭ Connect the test instrument to the device under test.
Figure 3.4: Connection Example for Voltage Measurement
• If a voltage of greater than about 10 V is present in the mea-
sured electrical circuit, its value is displayed in the U
IN field and
the “~” symbol appears for AC or polarity is displayed for DC.
The “+” symbol lights up if the positive pole is connected to
the fixed test probe, and “–” appears if the negative pole is
connected to the fixed test probe. “!” appears at the same
time as a warning. The START key is disabled!
Figure 3.2: Low Battery
Voltage
Figure 3.3: Low Battery
Voltage: Display
After Pressing the
START Key
Figure 3.5: Display of (Inter-
ference) Voltage
(Riso function)
Figure 3.6: Voltage
Measurement
(U
SPD function)
!