Which term describes a device that signals to control logic when a moving element reaches its end of travel?

Which term describes a device that signals to control logic when a moving element reaches its end of travel?

• A. Limit switch
• B. Proximity sensor
• C. Encoder
• D. Actuator

Answer: (A)

Limit switch is the device that signals control logic when a moving element reaches its end of travel. It uses a mechanical actuator attached to the moving part; when the end point is reached, the actuator is pressed and changes the switch’s contact state, producing a clear on/off signal for the controller. This provides a simple, reliable end-of-travel indication that’s robust in many industrial environments, and it’s easy to wire into a PLC or other logic. Proximity sensors detect presence without contact, and while they can sense objects, they aren’t inherently tied to a defined end-of-travel position. Encoders give detailed position or speed information, not just a single end-stop signal. An actuator is the component that moves things, not the sensor that signals the control system.

Limit switch is the device that signals control logic when a moving element reaches its end of travel. It uses a mechanical actuator attached to the moving part; when the end point is reached, the actuator is pressed and changes the switch’s contact state, producing a clear on/off signal for the controller. This provides a simple, reliable end-of-travel indication that’s robust in many industrial environments, and it’s easy to wire into a PLC or other logic.

Proximity sensors detect presence without contact, and while they can sense objects, they aren’t inherently tied to a defined end-of-travel position. Encoders give detailed position or speed information, not just a single end-stop signal. An actuator is the component that moves things, not the sensor that signals the control system.