NON CONTACT SENSOR
Photoelectric sensor • A photoelectric sensor is a device used to detect the distance, or presence of an object by using a light transmitter, often infra red, and a photoelectric receiver. Proximity sensor • A proximity sensor is a sensor able to detect the presence of nearby objects without any physical contact. • Proximity sensors can have a high reliability and long functional life because of the absence of mechanical parts and lack of physical contact between sensor and the sensed object.