How Does a Proximity Switch or Sensor Function?

Proximity devices, such as switches and sensors, detect the proximity of a physical object.

Detecting the proximity of an object without coming into physical contact with that object is a valuable technology in numerous industries and applications, ranging from machine vibration monitoring to controlling traffic lights. Proximity switches and sensors are two devices used in proximity detection.

Definitions

A proximity sensor is a device that detects motion and converts it into a signal that can be read by an instrument. A proximity switch is an electronic device that, once motion is detected, interrupts or breaks an electrical circuit in a device.

Proximity Sensor Operation

A proximity sensor transmits an electrostatic or electromagnetic field. The sensor detects the physical presence of an object based on changes in the field. A proximity sensor is divided into two parts, or halves. Detection of the object causes the two parts to move away from each other, which results in the activation of a signal.

Proximity Switches

Proximity switches emit beams of infrared light. Any reflection of this light resulting from the detection of an object is detected by a photodetector, which is a device capable of converting light into voltage. The light reflection triggers the switch to close or open an electrical circuit.

References

• Sensors Reference Center: Proximity Sensor
• "Sensors and Transducers"; Ian Robertson Sinclair; 2001
• "Sensors and Control Systems in Manufacturing"; Sabrie Soloman; 2009