Unitest TELARIS ERDE Bedienungsanleitung Seite 25

auxiliary earth and earth. The voltage drop be-
tween earth and probe is measured. The test
lead resistance from measurement instrument
to earth is included in the measurement. This
measurement is used to determine e.g. earth
resistance of foundation earths, building site
earths and lighting protection earth connec-
tions.
H
S
Figure 4: three-wire measurement
Locate earth rods for auxiliary ground, probe
and ground, in one line if possible, as described
in figure 4. The layout can also be realized by
tiangular shape. Distance between probe and
earth, or probe and auxiliary earth must be at
least 20 m. The test leads should not be paral-
lel to each other and should not cross to avoid
couplings.
Connect test leads to earth rods acc. fig. 4.
Select "3 pole" measurement by using measure-
ment selection switch (13).
Set contact voltage (11) by using key "UL" (14).
If required choose maunal frequency selection
by using key "auto/man" (16), and select test
frequency with key "f1/f2" (12).
Press key "Start" (14)
Read measurement result from display.
To verify the measurement, exchange the con-
nections of probe and auxiliary earth or move
the earth rod for the probe approx. 1...2m to-
wards the earth connector (or afterwards to-
wards the auxiliary earth) and measure again. If
the instrument shows similar measurement
E
results for all three measurement layouts, the probe
is located outside the voltage funnel generated by
earth and auxiliary earth in the reference earth area.
Are the measurement values not similar the probe
could be located inside the voltage funnel. To avoid
this there are two possibilities:
A: increase the distance between earth and aux-
iliary earth
or,
B: position the earth rod for the probe to one
point of the line outside the voltage funnel, as
shown in figure 5, and repeat the measure-
ment.
Firgure 5: Voltage funnel
After the measurement, selection can be made
between display of earth resitance (RE), auxil-
larx resistance (RS) and measurement current
(IM) by using key "Display" (8), depending on
the measurement result.
The connection sequence must be respected.
Otherwise the instrument will not be able to
carry out the measurement and indicates an
error message:
• the display "Probe" indicates a connection
error of S, E (interruptions, exchange also
with H or E)
• the "Limit IM" display indicates an interrup-
tion of the H connectors.
Also refer to display indications in chapter 7.0
Commissioning
25