Keithley 2450 Reference Manual page 107

Section 2: General operation Model 2450 Interactive SourceMeter® Instrument Reference Manual
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.
Sense current is negligible, therefore
Measure resistance is
2-80 2450-901-01 Rev. B/September 2013