In PLC input wiring, what does sourcing vs sinking refer to, and why is correct matching essential?

Prepare for the OCC SACA Sensor Logic Systems 1 (C-205) Exam. Study with detailed questions and insightful explanations. Get ready for your certification!

Multiple Choice

In PLC input wiring, what does sourcing vs sinking refer to, and why is correct matching essential?

Understanding where the current comes from and where it returns is what this is about. In a sourcing arrangement, the external device supplies the high-side voltage to the PLC input and the current path completes to ground. In a sinking arrangement, the input is completed to ground on the external side, while the other side provides the supply reference. Matching these paths is essential because the PLC input needs a defined reference and a proper current path to read a valid high or low signal. If you mix a sourcing device with a sinking input (or vice versa), you can leave the input floating, create a short, or force current through the wrong path, which can lead to unreliable readings or damage to the input or device feeding it. So always pair the device’s wiring style with the PLC input’s expected path and share a proper reference ground, ensuring safe, predictable operation.

Understanding where the current comes from and where it returns is what this is about. In a sourcing arrangement, the external device supplies the high-side voltage to the PLC input and the current path completes to ground. In a sinking arrangement, the input is completed to ground on the external side, while the other side provides the supply reference. Matching these paths is essential because the PLC input needs a defined reference and a proper current path to read a valid high or low signal. If you mix a sourcing device with a sinking input (or vice versa), you can leave the input floating, create a short, or force current through the wrong path, which can lead to unreliable readings or damage to the input or device feeding it. So always pair the device’s wiring style with the PLC input’s expected path and share a proper reference ground, ensuring safe, predictable operation.

More practice questions