1. Input/output wiring Diagram

2. Difference between PNP and NPN sensors
PNP sensors are sometimes called “sourcing sensors” because they source positive power to the output.
 NPN sensors are sometime called “sinking sensors” because they sink ground to the output. 
The term “load” identifies the device the sensor powers. The load could be a lamp, pneumatic valve, relay or PLC input.

3. PNP & NPN sensor

4. PNP sensor to PLC wiring (sinking)

5. NPN sensor to PLC wiring (sourcing)

6. NPN interface sinking input module

7. ControlLogix IB32 DC Input Module Connection (Sinking)

8. ControlLogix OB16I DC Output Module Connection (Sourcing)

9. PLC-5 IBD DC Input Module Connection (Sinking)

10. PLC-5 OBD DC Output Module Connection (Sourcing)

11. SLC-500 IB16 DC Input Module Connection (Sinking)

12. SLC-500 OB16 DC Output Module Connection (Sourcing)

13. S7 SM321 DI32x24V DC Input Module Connection (Sinking)

14. S7 SM322 DO16x24V DC Output Module Connection (Sourcing)

15. Modicon DDI 1602 24V DC Input Module Connection (Sinking)

16. Modicon DDO 1602 24V DC Output Module Connection (sourcing)

17. GE MDL 660 12/24V DC Input Module Connection (Sinking)

18. GE MDL 754 12/24V DC Output Module Connection (sourcing)

19. Analog Input Module