A device which is used to measure a quantity – such as the distance to an object or the speed of a robot.

An input device that sends information about its surroundings and lets it know the state of the world around it. This information in the form of electronic signals, or data. Sensors can provide only limited feedback to robots, so most robots of today are nearly deaf and blind, compared to the senses and abilities of even the simplest living things.

Instruments used as input devices for robots, which enable it to determine aspects regarding the robot's environment, as well as the robot's own positioning. Sensors respond to physical stimuli (such as heat, light, sound, pressure, magnetism and motion), and they transmit the resulting signal or data for providing a measurement, operating a control or both. (R15.06).