14/06/2026
⚡ Sinking vs Sourcing in PLC I/O – A Must-Know Concept for Automation Engineers! ⚡
One of the most common topics in PLC wiring and troubleshooting is understanding the difference between Sinking and Sourcing I/O.
🔹 Sinking Mode: The PLC provides a path to 0V (Ground), and current flows into the PLC input.
🔹 Sourcing Mode: The PLC provides +24V DC to the field device, and current flows out of the PLC output.
Understanding these concepts is essential for:
✅ Correct PLC wiring
✅ Sensor and actuator selection
✅ Troubleshooting field signals
✅ Preventing wiring mistakes
✅ Improving system reliability
Many commissioning and maintenance issues occur simply because the wrong sinking/sourcing configuration is used.
💬 Which type do you commonly use in your projects—PNP (Sourcing) or NPN (Sinking)? Let us know in the comments!