Rockwell Automation 1771-IR Series D RTD Input Module User Manual - Manual (Page 65)

Appendix
E
Publication 1771Ć6.5.129 - March 2000
2 and 4-Wire RTD Sensors
You can connect 2–wire and 4–wire sensors to the RTD module.
Before we show you how to do this, let’s examine the differences
between 2, 3 and 4–wire sensors.
A 2–wire sensor is composed of just that; a sensor and 2 lead wires.
Its schematic representation is shown below.
Connections for a 2–Wire Sensor
C
B
A
12950-I
A sensor requires at least three leads to compensate for lead
resistance error, that is, an error caused by resistance mismatch
between the lead wires.
Therefore, a 2–wire sensor cannot provide compensation for error
caused by lead wire resistance. We do not recommend that you use
2–wire sensors.
About 2 and 4-Wire
Sensors