A photoelectric switch, also called a photoelectric sensor, is a device that detects the presence or absence of an object by measuring changes in light intensity, typically by emitting a light beam and then detecting when that beam is interrupted or reflected by an object; key characteristics include non-contact detection, long sensing distances, high speed response, ability to detect various materials (including transparent ones), and wide application in industrial automation, material handling, and everyday devices like automatic doors and hand-wave faucets.
Key points about sensor switches: