What is 2 wire and 4 wire conection

please tell me 2 wire and 4 wire

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This picture may indicates all loop cases of “how to connect field instrument with PLC module”.

Left side is two wire instrument and right side is 4-wire instrument.

Any loop needs power to be activated

  • either from the module (internal) or from external source.

Dont connect source to source or load to load (then the loop wont work).

Whatever giving the loop power is called (ACTIVE) and other side will be just a load (PASSIVE).



Excellent information.