four wire measuring
The four-wire measurement is a metrological arrangement suitable for the measurement of small resistance values and resistance sensors. In contrast to the two-wire measurement, the four-wire measurement works with special connection terminals, the Kelvin terminals, with which the conductor resistances of the measuring leads are compensated.
In four-wire measurement, the DUT is supplied by a constant current source and the voltage drop across the DUT(resistance) is tapped by a high-impedance measuring device via two separate measuring leads. As a result, no current flows in the measuring leads and thus no voltage drop occurs.
Four-wire measurements are always used when the measuring resistance is very low and could be affected by the lead resistances of the measuring leads and the contact resistances of the measuring contacts. With this measurement technique, resistance values in the milli-ohm range can be measured.