Construction of Draw-wire linear position sensors！

Draw-wire linear position sensors（string sensor， string pots，yoyo sensor） measure the linear movement of a component through a highly flexible steel wire which is wound onto a drum by a durable spring-driven motor. The winding drum is linked axially to a multi-turn potentiometer, incremental encoder or absolute encoder. Roundss encoder provides the three sensors to output analog and digital signals.

The free end of the wire is attached to the moveable body,which need to be measured. A linear movement is transformed into a rotation by the draw-wire principle and converted into an electrical signal using a potentiometer to a proportional analog signal or to countable increments and absolute encoder to a digital signal.

A spring motor provides sufficient pre-tension of the wire. The spring motor is a coil spring with torque load, similar to those used in mechanical watch mechanisms. The further the wire is drawn out, the higher the tensioning force of the spring.

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