If a three-wire capacitive sensor has two terminals connected to the power supply, what should be connected to the output terminal?

• A. control input terminal
• B. power supply
• C. load
• D. ground

Answer: (A)

In a three-wire capacitive sensor, two wires supply power and the remaining wire is the signal output. After you wire the sensor to the power supply, the output terminal is intended to drive the control side of the system. That means connecting it to the control input terminal of a PLC or other controller—the load that consumes the sensor’s signal. The controller input is what completes the circuit and interprets the ON/OFF state from the sensor. Wiring the output to ground or directly back to power wouldn’t provide the proper control signal to the controller.