How to wire a PNP proximity switch to a PLC Check out the full blog post over at https://realpars.com/discrete-sensors-part-2/ In this video, you will learn how to wire a 3-wire DC sensor, like an inductive proximity sensor, to a PLC input card. For 3-wire discrete DC sensors, each digital input channel requires the connection of three wires. We’ll also learn that the SM321 card is constructed so as to accept only PNP-type sensors in a 3-wire configuration. The use of NPN sensors would require a