Manual

Gossen Metrawatt GmbH 79
17.2 Protective Conductor Resistance Measurement with Ramp Sequence
– Measurement at PRCDs with Current-Monitored Protective Conductor using the PROFITEST PRCD Test Adapter as an
Accessory ( PROFITEST MXTRA only)
Application
Protective conductor current is monitored for certain types of
PRCDs. Direct activation or deactivation of the test current
required for protective conductor resistance measurements of at
least 200 mA results in tripping of the PRCD and thus to interrup-
tion of the protective conductor connection. Protective conductor
measurement is no longer possible in this case.
A special ramp sequence for test current activation and deactiva-
tion in combination with the PROFITEST PRCD test adapter per-
mits protective conductor resistance measurement without trip-
ping the PRCD.
Ramp Function Time Sequence
Due to the physical characteristics of the PRCD, measuring times
for this ramp function amount to several seconds.
If test current polarity is revered, additional waiting time is also
required during polarity reversal.
This is programmed into the test sequence in the “automatic
polarity reversal” operating mode.
Reverse polarity manually, e.g. from
“+pole with ramp” to “-pole
with ramp” . The test instru-
ment then detects the reversal of current
flow direction, stops measurement for the
required waiting time and simultaneously
displays a corresponding message (see
figure at right).
PRCD Tripping due to Poor Contacting
Good contact must be assured between the test probes at the 2-
pole adapter and the device under test or the sockets at the
PROFITEST PRCD test adapter during measurement. Interrup-
tions can result in considerable test current fluctuation which
causes the PRCD to trip under unfavorable conditions.
If this is the case, tripping of the PRCD is
automatically detected by the test instru-
ment and indicated by a corresponding
error message (see figure at the right). In
this case as well, the test instrument
automatically takes subsequently
required waiting time into account before
you can reactivate the PRCD and start the measurement over
again.
Connection
➭ Read the operating instructions for the PROFITEST PRCD
adapter, in particular section 4.1. It includes connection in-
structions for offset measurement and for protective conduc-
tor resistance measurement.
Selecting the Polarity Parameter
➭ Select the desired polarity parameter with ramp.
Measuring ROFFSET
➭ Perform offset measurement as described on page 77, in
order to assure that the test adapter’s connector contacts are
not included in the measurement results.
Note
The offset is only retained in memory until the polarity
parameter is changed. If measurement is performed with
manual polarity reversal (+pole or -pole), the offset mea-
surement has to be repeated in both polarities before
each measurement.
Measuring Protective Conductor Resistance
➭ Determine whether or not the PRCD is activated. If not, acti-
vate it.
➭ Perform protective conductor measurement as described in
section 17.1 above. Start the test sequence by briefly press-
ing the ON/START ▼ key. The predetermined duration of the
measuring phase can be extended by pressing and holding
the ON/START ▼ key.
Start Measurement
The symbol shown at the right appears during the mag-
netization phase (rising curve) and the subsequent mea-
suring phase (constant current).
If measurement is aborted already during the rising phase, no
measurement results can be ascertained or displayed.
After measurement, the demagnetization phase (falling
curve) and subsequent waiting time are indicated by the
inverted symbol shown at the right.
No new measurements can be started during this time.
Measurement results cannot be read and measurement
with the same or another polarity cannot be started until
the symbol at the right appears.
Measuring Phase Demagnetizing
and Waiting Time
Result
Time [s]
Rising
Phase
Test Current [A]
01 3 6
0.25
Before Polarity Reversal
or
Restart
Representation of Measuring and Waiting Times for
Protective Conductor Resistance Measurement at
PRCDs with the PROFITEST MXTRA