Industrial Engineer · phase 2 of 16
Sinking / Sourcing
DC circuit convention describing whether a device provides the current return path or supplies current to the load.
The Explain card
- Plain English
- Sinking and sourcing describe which way current flows through a DC input or output. A sourcing device pushes current out to the load, and a sinking device pulls current in to common.
- Example
- A PNP sensor sources current, so it needs an input card that sinks. Wire it to a sourcing input card and the point never turns on.
- Why it matters
- The mismatch is the most common wiring error in a new panel and it produces no fault, just an input that stays off. Every sensor, card and drawing has to agree before power goes on.
- Hook
- Current has to have somewhere to go, and the card decides where.
Where it sits in the deck
Phase 2: PLC I/O and Field Signals
Where the controller meets the machine: discrete and analog signals, the wiring conventions behind them, and the field devices that send them.
