Draw-wire encoders are widely used in industrial automation, robotics and other areas where precise position measurements are required. They essentially consist of a wire, the spring mechanism, the encoder, the coil and the surrounding housing
If the measuring object moves, the wire is pulled out of the housing and the coil rotates. The encoder on the coil measures the rotational movement and converts it into an electrical signal. Since the circumference of the coil is known, the rotational movement can be converted into an exact change in length.