Which device is used to sense the position of a machine member?

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Position sensing of a moving machine member is best accomplished with a device that provides a defined signal when the part reaches a specific point. A limit switch is designed for this exact purpose: a mechanical actuator (like a lever or plunger) is triggered by the moving member at a fixed position, sending a clear electrical signal to the control system to stop, start, or interlock actions. This gives a precise end-of-travel indication, which is essential for controlling the machine’s movement and safety. Proximity sensors detect presence within a range but don’t inherently define an exact position. Photoelectric sensors detect objects using light for presence or interruption sensing, not precise travel position. Thermocouples measure temperature, not position. So the limit switch best fits the role of sensing the position of a machine member.