Draw-wire displacement sensors are used to measure the length of pipes being processed to fulfill orders. The sensor works by connecting a wire to a movable stop on the measurement table that pipes are inserted onto. As the stop moves, the wire extends and the sensor measures the displacement to calculate the total length of pipes. Key features of the sensor include a measuring range of up to 7.5 meters, 1mm resolution, and operating in air between 10-35 degrees Celsius to accurately measure pipe lengths in a dirty industrial environment.