Four-terminal resistivity measurement (DET4TD, DET4TR2, DET4TC2 and DET4TCR2)
The DET4TD2, DET4TR2, DET4TC2 and DET4TCR2 can be used to make soil resistivity measurements. The resistivity value can
be derived from the four-terminal resistance reading made by the instrument and the particular separation and depth of the
stakes.
1.
Ensure the rotary selector switch is in the
OFF
position.
2.
Connect the instrument as shown in Figure 27.
Figure 27: instrument connection for measuring four-terminal resistance
3.
Set the rotary selector switch to the
4P
position.
4.
Select the desired test voltage using the
25 V/50 V
button.
5.
DET4TC2 and DET4TCR2 only: Select the desired test frequency using the
Hz
button.
6.
Press and release the
TEST
button [by holding the
TEST
button, the resistance measurement will be continually
updated].
7.
The instrument will perform pre-measurement check, the status of which will be indicated on the display.
8.
The four-terminal resistance reading will be displayed as shown in Figure 28.
Figure 28: example four-terminal resistance reading (DET4 display shown)
9.
A soil resistivity value can be derived from the resistance reading and the stake geometry.
Note
:
The instrument will display the warning triangle and an excessive noise voltage indicator if the ground noise voltage
is above 40 V pk-pk (14 Vrms).
The instrument will display the warning triangle and a voltage over-range condition if the ground noise voltage is
above 100 V – no resistance reading is possible under this condition.
