Manual

26 Gossen Metrawatt GmbH
8.2.2 Performing Insulation Measurement
➭ When the device under test is voltage-free, activate the mea-
surement by pressing, or pressing and holding, the Start soft-
key on the instrument or on the probe. See below for further
information.
➭ Don’t read the measurement results until the display has set-
tled in. The high-voltage symbol next to the battery level dis-
play blinks during measurement.
Auto-ranging is active during insulation resistance measurement.
A DATA function which is matched specifically to the insulation
measurement can be activated for automatic retention of valid
measured values (see section 7.2.1).
Measurement-Specific Setting: Press and Hold the Start Key
The instrument can be configured such that measurement is acti-
vated when the Start softkey is pressed or pressed and held, and
ended when the key is released.
Either the Start softkey on the instrument or the Start key on the
Z270S probe
(METRAHIT IM XTRA BT and METRAHIT IM E-
DRIVE BT only) can be pressed and held.
Attention!
!
Measured value storage is not possible with the Store key
on the probe if the Start key on the probe is pressed and
held to activate measurement!
If the Start key on the probe is pressed and held, press-
ing the Store key on the probe aborts measurement with-
out storing the measured value.
Press the Store key on the instrument in order to save the
measured value.
Refer to section 7.6 on page 20 for more information
concerning measured value storage and the Z270S
probe.
➭ Press the MENU key.
➭ Press the Setup for present measurement softkey.
➭ Switch to the submenu with the help of the  scroll key.
➭ Select the Hold Start Button parameter with the
 scroll keys.
➭ Acknowledge the selected parameter by pressing the OK key.
➭ Select Yes or No with the help of the
 scroll keys.
➭ Acknowledge your change with the OK key. The entry cursor
once again marks the entire parameter line.
➭ The display is returned to the measuring function by pressing
the ESC key three times.
> Setup for Present Measurement
 Hold Start
Button
  Yes/N o
3x
Automatic Detection of Interference Voltage During Insulation
Measurement
If the instrument detects interference voltage of roughly > 15 V AC or
>25VDC (condition: U
ext
 U
INS
, e.g. Riq < 100 k at 100 V, see
page 62, footnote 1), the instrument is switched automatically to
voltage measurement and the currently measured voltage value is
displayed as Uext.
Note
A dead zone results in erroneous measurements for
automatic interference voltage detection during insulation
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 mea-
suring voltage, the two voltages neutralize each other).
Manual switching to insulation resistance measurement is dis-
abled for as long as voltage is applied to the test terminals.
If interference voltage is no longer present, insulation measurement
can be started by pressing the
Start softkey once again.
Attention!
!
If “Error” appears at the display, the cable (the device
under test) is most likely capacitively charged to a signifi-
cant extent. Remedy:
Short circuit the cable (the device under test). Repeat the
measurement.
8.2.3 Ending the Measurement and Discharging
➭ Press the Stop softkey in order to end the measurement. If the
Press and Hold the Start Key setting has been activated, release
the Start key (see page 26).
A warning is displayed during the discharging
procedure which isn’t cleared from the display
until applied voltage
Uext is 0000 V.
The instrument’s internal 1 M resistor causes
rapid discharging. Contact between the object
and the instrument must not be interrupted.
Do not disconnect the DUT until voltage has fallen below 25 V and the
warning has been cleared from the display!
Note
Voltage measurement in the RISO or COIL switch position
is used primarily for interference voltage detection before
the respective measurement.
Use the V , V or V switch position in order to per-
form precise voltage measurements.
8.3 Inter-Turn Short Circuit Measurement – COIL Function
(METRAHIT IM XTRA BT and METRAHIT IM E-DRIVE only)
In combination with METRAHIT IM XTRA BT and METRAHIT IM E-
DRIVE BT multimeters, the COIL TEST ADAPTER (COIL ADAPTER
50mH) and the COIL ADAPTER XTRA make it possible to measure
inter-turn short circuiting. The adapters are universally suitable for
numerous electric motors with various power ratings.
Note
The Z720S probe cannot be used when measuring inter-
turn short circuiting with an adapter.
8.3.1 Inter-Turn Short Circuit Measurement with the COIL TEST
ADAPTER
In combination with the optional COIL TEST ADAPTER, inter-turn
short circuit measurements with a test voltage of 1000 V are pos-
sible within an inductance range of 10 μH to 50 mH (100 Hz). This
range corresponds to motors in accordance with DIN standards
with power ratings of roughly 15 kVA to 80 MVA.
A time value which depends on the inductance of the respective
coil is ascertained for each motor coil or coil combination, one
after the other, during this measurement with high-voltage. A
comparison of the time values makes it possible to check the
motor coils for symmetry, and thus to detect an inter-turn short
circuit.
MENU
OK
ESC
+
–
0V!
Discharge