Resistance Measurement
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7-6
If an Offset Correction is not carried out, a measurement value R
m
is obtained, which
is composed of the sum of all the resistances that exist in the measurement circuit
(measurement path), and is too high by the lead resistance.
R
m
= R + R
L
+ R
L
The measurement cables that are often used, with a length of 1m, have a resistance of
approx. 10-20mΩ. If the resistance to be measured is 100Ω, this already results in an
error of 0.04 %.
With low resistance values, especially in the 100 Ohm range, the lead resistance
makes itself strongly visible. For that reason, a four-wire resistance measurement is
recommended for these ranges.
Diagram: Principle of 2-wire resistance measurement
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