How to connect a 4 wire PT100 or PT1000 sensor to a 3-wire RTD input.
EcoStruxure Building Operation
Building Operation I/O Module 16 Ch RTD
Some PT100/PT1000 sensors have only 3 terminals to connect to.
The wires to the sensor are often color marked in pair, like two red cables and two white cables.
As we only have 3 terminals to connect to, the solution is to only connect 3 of the cables, and not connect the 4th cable.
As the RTD device also measure the resistance of the cables, to make a correct temperature reading, it is important that all three wires used do have the same length and resistance.
Therefore, the fourth wire should NOT be connected in parallel, it has to be un-connected.