How to Wire a Sensor to PLC: NPN vs PNP

Sensor to PLC wiring

Sensor output type (NPN/PNP) must match PLC input type (sink/source).

NPN vs PNP

Not sure — PNP NO.

Wiring

• 3-wire PNP: brown +24V, blue 0V, black → DI
• Analog 4-20 mA: 2-wire → AI module

FAQ

Identify NPN/PNP?

Marking or multimeter.

NPN to Siemens?

Yes, switch to sink.

How many sensors?

As many as DI/AI inputs.

4-20 mA vs 0-10 V?

4-20 mA for industrial, long cables.

Separate PSU?

With 10+ sensors — yes.

Summary

Sensors: inductive, pressure. PLCs: Delta, Siemens.