The draw wire sensor is also called the cable sensor, the cable electronic ruler, and the cable encoder. The rope displacement sensor is an ingenious structure of the linear displacement sensor. It fully combines the advantages of angle sensors and linear displacement sensors. It becomes a sensor with small installation size, compact structure, large measuring stroke and high precision. The journeys range from a few hundred meters to tens of meters. Economical traction rope and heavy-duty traction rope, economical traction rope is cheap, heavy-duty traction rope has thick steel wire rope, 1.5MM, 2.0MM, the shell is cast, and the measuring plate has a guide.