7½ Digit Graphical Sampling Multimeter Reference Manual Section 2:
DMM7510-901-01 Rev. B / May 2015 2-105
Accuracy of 2-wire resistance measurements
The 2-wire sensing method has the advantage of requiring only two test leads and provides faster
reading rates.. However, as shown in the following figure, the total lead resistance is added to the
measurement. This can seriously affect the accuracy of 2-wire resistance measurements, particularly
with low resistance values.
Figure 66: Two-wire resistance sensing for high impedance DUT
Minimizing the effect of lead resistance with 4-wire testing
The 4-wire sensing method, shown in the following figure, minimizes or eliminates the effects of lead
resistance. The effects of lead resistance are minimized by measuring the voltage across the resistor
under test with a second set of test leads. The current through the sense leads is negligible, and the
measured voltage is essentially the same as the voltage across the resistor under test. Note that the
voltage-sensing leads should be connected as close to the resistor under test as possible to avoid
including the resistance of the test leads in the measurement.
Figure 67: Model DMM7510 4-wire resistance sensing
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