Manual

Gossen Metrawatt GmbH 67
15.8 Earthing Resistance Measurement, Battery Powered, “Battery Mode” – 4-Pole ( PROFITEST MPRO & PROFITEST MXTRA only)
4-Wire Method
The 4-wire method is used in the case of high cable resistance
between the earth electrode and the instrument terminal.
The resistance of the cable between the earth electrode and the
“E” terminal at the instrument is measured in this case.
Connection
➭ Position the spikes
for the probe and the auxiliary electrode at least 20, respec-
tively 40 meters from the electrode (see figure above).
➭ Make sure that no excessively high contact resistances occur
between the probe and the ground.
➭ Attach the PRO-RE adapter (Z501S) to the test plug.
➭ Connect the probes, the auxiliary electrode and the electrode
via the 4 mm banana plug sockets at the PRO-RE adapter.
In doing so, observe labeling on the banana plug sockets.
Note
In the case of the 4-wire method, the earth electrode is
connected to the “E” and “ES” terminals with two separate
measurement cables, the probe is connected to the “S”
terminal and the auxiliary earth electrode is connected to
the “H” terminal.
Note
The measurement cables must be well insulated in order
to prevent shunting. In order to keep the influence of pos-
sible coupling to a minimum, the measurement cables
should not cross each other or run parallel to each other
over any considerable distance.
Select Measuring Function
Select Operating Mode
The selected operating mode is displayed inversely:
white battery icon against black background.
Set Parameters
❏ Measuring range: AUTO, 50 k, 20 k, 2 k, 200 , 20 
❏ Connection: 4-pin
❏ Transformer ratio: irrelevant in this case
❏ Distance d (for measuring

E
): irrelevant in this case
Start Measurement
Potential Gradient Area
Information regarding
suitable positioning of
the probe and the auxiliary earth electrode can be obtained by
observing voltage characteristics ordissipation resistance in the
ground.
The measuring current from the earth tester which flows via the
earth electrode and the auxiliary earth electrode causes a given
potential distribution in the form of a potential gradient area (cf.
page 68). Resistance distribution is analogous to potential distri-
bution.
Dissipation resistance of the earth electrode and the auxiliary
earth electrode differs as a rule. The potential gradient area and
the resistance gradient area are thus not symmetrical.
Dissipation Resistance of Small Scope Earth Electrodes
The arrangement of the probe and the auxiliary earth electrode
are very important for correct determination of the dissipation
resistance of earth electrodes.
The probe must be positioned between the earth electrode and
the auxiliary earth electrode within the so-called neutral zone (ref-
erence earth) (cf. page 68).
The voltage or resistance curve is thus nearly horizontal within the
neutral zone.
Proceed as follows in order to select suitable probe and auxiliary
earth electrode resistances:
➭ Drive the auxiliary earth electrode into the ground at a dis-
tance of roughly 40 meters from the earth electrode.
➭ Position the probe halfway between the earth electrode and
the auxiliary earth electrode and determine earthing resis-
tance.
➭ Reposition the probe 2  3 m closer to the earth electrode,
and then 2  3 m closer to the auxiliary earth electrode and
measure earthing resistance in each position.
If all 3 measurements result in the same measured value, this is
the correct earthing resistance. The probe is in the neutral zone.
However, if the three measured values for earthing resistance dif-
fer from each other, either the probe is not located in the neutral
PROFITEST MPRO / PROFITEST MXTRA
S HESE
E
SH
 20 m  20 m
Earthing Resistance Measurement
According to the 4-Wire Method
R
E