Amprobe Telaris-Earth-Test Earth-Resistance-Tester - Manual (Page 19)

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Measurement of the Specific Earth resistance in accordance with
the 'Wenner' method
• To perform this measurement the user requires the Amprobe Earth Measurement Set
To calculate the spreading resistance of earths and earthing systems the specific earth
resistance must be determined. To calculate the specific earth resistance, the measured earth
resistance is used in the formula: ρ = 2*
π
*a*RE.
This measurement is performed using four earth rods inserted into the soil to be tested in
one line at the same distance 'a' apart. The four earth rods are inserted into a depth of
maximum 1/5th of the distance 'a'.
The earth resistance is detected up to the depth of the distance 'a'. To avoid faulty
measurements metal pipes, cables in the earth, or in open areas under earth waterways, or
roots installed or located in parallel must be taken into account. Additionally, the specific
earth resistance is subject to seasonal weather-related variations.
Figure 7: Specific Earth resistance measurement
1) Place the four earth rods for E, ES, S, H in one line, in accordance with Figure 7. The
distance between each probes must match the value used in the formula. Carefully
place the test leads making sure that the test leads are not parallel to each other and
do not cross to avoid coupling.
2) Connect test leads to earth rods according to figure 7.
3) Selct “4 pole“ measurement by using selection switch (13).
4) Set contact voltage by using key “UL“ (11).
5) If required choose manual frequency selection by using key “auto/man” (16), and
select test frequency with key “f1/f2” (12).
6) Press key "Start"(14), read measurement result on display.
H
S
ES
E
PAEB30872261:Layout 1 12.12.2007 12:06 Uhr Seite 17