Fourwire

Fourwire is a term used in electronics to describe a four-conductor arrangement used for measurement or signaling. It refers to configurations that separate the current-carrying conductors from the sensing or signal conductors in order to minimize the influence of lead resistance, contact resistance, and impedance on measurements or communications.

In four-wire resistance measurements, two wires supply a known current through the device under test, while the other two wires measure the resulting voltage drop across the same device. The sensing conductors carry negligible current, so their resistance does not affect the measured voltage. This Kelvin connection is essential for accurate measurements of small resistances and is widely used in metrology, calibration, and temperature sensing.

Four-wire configurations are especially important for precision resistance temperature detectors (RTDs) such as Pt100 or Pt1000 sensors and for low-value shunts in instrumentation. By eliminating lead and contact errors, four-wire setups provide higher accuracy than two-wire or three-wire arrangements, particularly at low resistance values or when temperature and connection quality vary.

In instrumentation, four-wire measurements are implemented with specialized equipment or Kelvin-sensing inputs on multimeters, LCR meters, and bridge circuits. In telecommunications and signaling, four-wire circuits separate transmit and receive paths to enable full-duplex operation and reduce interference, as opposed to two-wire circuits which share a single pair and often require hybrid separation.

Overall, the term fourwire is a generic descriptor for any four-conductor arrangement designed to improve accuracy and isolation in measurement and signaling contexts.