MDtest (100-140 V) - User’s Manual 4 Measurements
4.3.1 Test lead resistance compensation
Compensation means that the test lead resistance is measured and then
automatically memorized and subtracted from all Rpe measurements.
The real earth bond resistance is thus displayed. The compensation
constant remains in the instrument’s memory even if the instrument
is switched off. Therefore, the lead compensation is valid until a new
compensation is carried out.
Procedure:
• Press the [3 RPE] key and release it.
• Plug the test lead with the test tip into the RPE terminal.
• Plug the test tip of the test lead either into the PE terminal or press it
against the ground pin of the Test Socket 1. If you use two test leads (which
are connected to the PE terminal and the RPE terminal), then make a short-
circuit of their test tips.
• Press the [TEST] key and release it.
• Press the [Cal] key and release it. The measured value is saved.
The compensation is effective for test lead resistance <2.00 Ω. If the test lead
resistance is >10.00 Ω and the compensation procedure has been carried out, com-
pensation is cancelled and all the following displayed results are the sum of the earth
bond + test lead resistance. The CAL symbol is not displayed.
If compensation is active (it means that test lead resistance <2.00 Ω was memo-
rized), then the CAL symbol is displayed during Rpe measurements.
If the measured value is less than the saved compensation value during measure-
ment (after subtraction, the memorized resistance will result in a negative number),
the display shows the absolute value and the CAL symbol appears inversely. The
cause may be replacing test leads for shorter ones with less resistance. In this case,
it is necessary to re-compensate the test leads resistance.
4.3.2 Protective earth resistance
Procedure:
• Press the [3 RPE] key and release it.
• Plug the test lead with the test tip into the RPE terminal.
• Connect the tested appliance:
– One-phase appliance with a movable power supply cord – plug in its
mains plug to Test Socket 1.
– Three-phase appliance with a movable power supply cord – connect the
PE pin of its plug to the instrument’s PE terminal by means of the
optional test lead + crocodile clip.
– Hard-wired appliance – firstly disconnect the appliance from the
mains! Connect its point of PE connection to the instrument’s PE ter-
minal by means of the optional test lead + crocodile clip.
c
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