what is a sensor
A sensor is a device that detects and responds to some type of input from the physical environment. The specific input could be light, heat, motion, moisture, pressure, or any one of a great number of other environmental phenomena.The output is generally a signal that is converted to human-readable display at the sensor location or transmitted electronically over a network for reading or further processing.he liquid contained expands and contracts in response, causing the level to be higher or lower on the marked gauge, which is human-readable. An oxygen sensor in a car's emission control system detects the gasoline/oxygen ratio, usually through a chemical reaction that generates a voltage.