Flow Ctrl Tech Engineering

Temperature Sensor Drift: RTD Lead Resistance, Thermocouple Cold-Junction & Extension Wires

Field guide to identifying temperature calibration errors: 2-wire vs 3-wire vs 4-wire PT100 RTDs, thermocouple extension wire mismatch, and cold-junction compensation (CJC) drift.

  • A 2-wire PT100 RTD suffers approximately 2.5°C of positive error for every 1 Ohm of copper cable lead resistance.
  • 3-wire and 4-wire RTD circuits mathematically cancel out lead wire resistance variations.
  • Thermocouples require specialized alloy-matched extension wires; standard copper creates secondary unintended thermocouple junctions.

Flow Ctrl Tech Engineering: Turnkey industrial automation, PLC programming, SCADA development, HMI, fieldbuses, and IIoT architectures. Contact our engineering center at [email protected] or phone +91 91110 91005.