Draw Wire Unit

 

The basic operating principle of a draw wire encoder shows below: a rotary encoder is coupled to a spring loaded-reel by using a mechanical coupling device, internal to the housing of the reel.

A cable is wound around the reel, which is usually a metal braid type. The braided cable is anchored to the drum of the reel and wrapped many times around it.

The opposite end of the cable passes through an exit port of the housing and is terminated with an anchoring device such as a clevis or loop to attach, in order to measuring the moving mechanism. As the cable is pulled, the drum is rotated and the linear motion is translated into rotary motion, at which point the draw wire encoder encodes the information into an electric signal.