Which device senses the position of a machine member via mechanical means and converts that position into an electrical signal?

• A. Limit switch
• B. Proximity sensor
• C. Photoelectric switch
• D. Pressure switch

Answer: (A)

A limit switch uses a physical actuator that the moving machine member pushes or presses as it reaches a specific position. This mechanical action moves internal contacts, creating or breaking an electrical connection. The result is a clear electrical signal that indicates that the part has reached the end of travel or a predefined position. This direct mechanical-to-electrical conversion is what makes it the right fit for sensing position.

Other sensors don’t rely on direct mechanical actuation by the moving part. Proximity sensors detect presence without contact using magnetic, inductive, or capacitive fields and then produce a signal. Photoelectric switches use light beams to detect objects or positions, again without physical contact. Pressure switches respond to changes in fluid or gas pressure, not the position of a machine member.