This means that interference has been detected which may impair the accuracy of the measurement. In particular, the reading
could be lower than the actual resistance. The resistance of the electrode or system must be verified by an alternative method.
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.
The instrument will display the warning triangle above 2 A – no ART testing is possible under this condition.
The instrument will display the warning triangle and an over-range condition above 20 A – no ART testing is
possible under this condition.
Ensure that the MCC CLAMP jaw mating surfaces are free of dust and contamination and that they contact
completely when the MCC CLAMP is closed.
Currents carried by conductors in close proximity to the MCC CLAMP may affect calibration and reduce the
accuracy of measurements made.
Three-terminal resistance measurement with lead-null using ART (DET4TC2 and DET4TCR2)
In certain circumstances, the resistance of the test leads 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.
Before making a measurement using ART, please follow the procedure contained in the section on MCC CLAMP calibration.
1.
Ensure the rotary selector switch is in the
OFF
position.
2.
Connect the instrument as shown in Figure 33.
Figure 33: instrument connection for measuring three-terminal resistance with lead-null using ART
3.
Close the MCC CLAMP around the conductor under test.
4.
Set the rotary selector switch to the
4P
position.
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 checks, the status of which will be indicated on the display.
8.
The three-terminal resistance reading with lead-null using ART will be displayed as shown in Figure 34.
Figure 34: example three-terminal resistance reading with lead-null using ART (DET4 display shown)
