Position sensors measure the position and movement of an object, relative to a reference point. These sensors are available as linear position sensors, angular position sensors or multi-axis sensors. Linear position sensors detect the movement of an object in a straight line. They consist of a ferromagnetic core and windings, enclosed in a housing. These sensors are very reliable and robust, and ideally suited to harsh or hostile environments. Angular position sensors calculate the angular movement of an object, in terms of the number of rotations required to change from one orientation to the other. These sensors find use in several automotive and industrial applications, such as steering wheel positioning, sensing float levels and setting flow meters, and in robotics. Position sensors include encoders and inertial measurement units. When the sensors detect motion, the encoders emit a digital signal revealing position, velocity and direction of the object. Linear position sensors use linear encoders and angular position sensors use rotary encoders. Draw wire encoders co-opt a wire draw mechanism with a flexible cable and a spring-loaded spool to measure linear speed and position of the object. The rotation of the drum is proportional to the length under measurement, and the encoder records the output.