Four-terminal sensing

Four-terminal sensing is used in some ohmmeters and impedance analyzers, and in wiring for strain gauges and resistance thermometers.

For example, an LCR bridge instruction manual recommends the four-terminal technique for accurate measurement of resistance below 100 ohms.

Since almost no current flows to the measuring instrument, the voltage drop in the sense leads is negligible.

If the force and sense connections are exchanged, accuracy can be affected, because more of the lead resistance is included in the measurement.

It is common to provide 4-wire connections to current-sensing shunt resistors of low resistance operating at high current.