How we can connect 4 wire RTD to PLC cards?
Two Options are there to connect 4 wire RTD to PLC.
First option is to use RTD-mA converter.
RTD-mA converter (Transmitter) is usually a better option that wiring RTD directly to the PLC card.
There are advantage of using this method.
1.Reduce the cost by not using a different type of PLC input card.
2.Some PLC card do not allow individual calibration of RTD channels.
2nd method of connecting 4 wire RTD to PLC input.
It is possible to connect a 4 wire RTD to a 3 wire input by just not connecting the sense wire. You can also connect to 2 wire input by not connecting either sense wires.
For every sense wire you do not connect the accuracy of the temperature measurement in your controller is reduced.