Why do some temperature sensors have 2 wires, others 3 or 4?

When it comes to RTDs (Resistance Temperature Detectors), wire configuration matters.

  • 2-wire RTD: Simplest, but affected by lead wire resistance.

  • 3-wire RTD: Most commonly used; compensates for lead resistance assuming all wires are equal.

  • 4-wire RTD: Most accurate; eliminates lead wire resistance entirely using a full Wheatstone bridge.

Choosing the right configuration depends on your accuracy needs, distance from transmitter, and budget.