Most ultrasonic sensors are based on the principle of measuring the propagation time of sound in the air. Ultrasonic frequencies outside the range of human hearing are emitted by the sensor. Sonic energy reflected by an object or target is picked up by the sensor’s receiver.","The highly integrated and extremely powerful Baumer sensors are capable of sensing objects irrespective of their color, surface properties or transparency and of measuring the distance from the sensor to a target. Ultrasonic sensors are extremely resistant to dirt. They are not impaired by dust, smoke, vapors or other contaminants.