what is the difference between 3 lead RTD and 4 lead RTD?
Answers
3-lead RTD constructions result in canceled lead-wire resistance error only if the instrumentation can measure true 3-wire resistance.
Lead-wire resistance error cancellation is most effective when all the lead wires have the same resistance. Using 3 wires of the same AWG, length, and composition will typically result in lead-wire resistances matched within 5%. The graph below shows the temperature error from lead-wire of various sizes and lengths, for a 3-lead 100-ohm platinum RTD at 100°C.
4-lead RTD constructions result in canceled resistance only if the instrumentation can measure true 4-wire resistance. True 4-wire resistance measurement will effectively cancel leadwire resistance error even if all 4 wires are not the same AWG, length, and/or composition…