SENSORS
PNP and NPN sensor outputs
An active PNP output switches toward positive supply; an active NPN output switches toward 0 V.
INTERACTIVE EXAMPLESIMULATION
The principle
With a common 24 V DC transistor output, an active PNP sensor supplies positive voltage at its output. An active NPN sensor pulls its output toward 0 V. The PLC input and wiring must match the output type.
An example
Switch between PNP and NPN to see the active output potential.
Important
Always check the wiring diagram of the exact sensor and PLC input card. Sourcing and sinking terminology depends on the viewpoint.