Prema DMM 5017 - Resistance Measurement; Two-Wire Resistance Measurement

7 Operating Instructions
_____________________________________________________________________________________________________________________________________
7-5
7.2 Resistance Measurement
The resistance measurements of the 5017 are carried out through the DC Current
method in a 2-wire or 4-wire connection.
A constant current (I) is forced through the resistance to be measured (R); the same
current simultaneously flows through a known internal range resistance. The voltage
drop across the resistance R is measured, and its relationship to the voltage drop
across the internal range resistance is noted. In this manner, resistance measurement
is not influenced by aging or drifting of the reference voltage source.
Two-Wire Resistance Measurement
If resistance measurements are carried out in two-wire mode, then it is important to do
a careful compensation for lead resistances and thermal voltages, through the use of
the offset correction procedure, especially when measuring small resistances (< 1kΩ).
To do this, the two measurement cables are connected by their clamps, producing a
short circuit, then an Offset Correction is triggered with the
ZERO
key.
Potential error sources, like lead resistance, contact resistance, and thermal voltages at
the connections between different metals, are thereby eliminated.