Proximity Sensor
A proximity sensor detects the presence of an object without physical contact and switches its output when the target enters the sensing range. Inductive sensors detect metal targets by generating an oscillating electromagnetic field; capacitive sensors detect metals, liquids and many non-metallic materials through changes in capacitance; magnetic and ultrasonic types are also used. Applications include position detection, end-of-travel sensing, speed and rotation monitoring, and valve position feedback. Selection parameters include rated sensing distance, target material and correction factor, flush or non-flush mounting, housing size (for example M12, M18 or M30), output type (PNP, NPN, NAMUR or analogue), supply voltage, switching frequency and IP rating. Inductive and capacitive proximity switches are covered by IEC 60947-5-2, and NAMUR sensors for intrinsically safe circuits follow IEC 60947-5-6.
Examples
- Inductive sensor for valve open/closed feedback
- Capacitive sensor for level detection in a hopper
- Speed monitoring on a conveyor pulley