New procedure for the monitoring of hydraulic cylinder - A new sensor of IBJ Technology from PVDF arrays for the measurement of the piston position with ultrasonic achieves high local dissolution, how it was unequalled for sensors on ultrasonic basis so far. A PVDF foil (ultrasonic sensor array) lies full-laminar on the cylinder wall. The single sensors of the array are queried over multiplexers lively and. The patented evaluation procedure works without disturbing absorption influences and without temperature dependences. The measurement of longer procedure distances of the piston is possible by lining up of several sensor arrays.