Device and method for monitoring the position of a piston rod

摘要

Device for controlling the position of the shaft of a jack (1) comprising a cylinder (3) inside which slide a shaft (5) and piston (6). The jack has an ultrasonic transducer (7) for determining the position of the shaft. The transducer is placed adjacent to the shaft so that it transmits waves obliquely into the shaft. The position of the shaft is determined from the time of flight of the ultrasonic waves within the shaft.