Three-terminal resistance measurement with lead null (DET4TD2, DET4TR2, DET4TC2 and DET-
4TCR2)
In certain circumstances, the resistance of the test lead connecting to the electrode under test may itself form a significant
part of the measurement electrode resistance. This effect can be eliminated using the lead-null technique described in this
section.
1.
Ensure the rotary selector switch is in the
OFF
position.
2.
Connect the instrument as shown in Figure 25.
Figure 25: instrument connection for measuring three-terminal resistance with lead-null
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 three-terminal resistance with lead-null reading will be displayed as shown in Figure 26.
Figure 26: example three-terminal resistance with lead-null reading (DET4 display shown)
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.
