| 摘要 |
PROBLEM TO BE SOLVED: To realize acoustic coupling between a diaphragm and the wall of container by interposing a coupling layer between the diaphragm and the wall of container thereby blocking formation of air layer between them and avoiding abrupt variation of impedance. SOLUTION: In order to monitor the upper and lower limit levels Hmax, Hmin of a liquid 11 filling a container 10, filling level sensors 13, 15 are fixed to the outside of container wall 12 and connected with a diaphragm and evaluation electronic circuits 14, 16. The sensors 13, 15 determines whether the liquid 11 in container 10 reaches the height of sensors 13, 15 or not through the container wall 12. The sensors 13, 15 are constituted as an ultrasonic sensor for delivering an ultrasonic pulse toward the container wall 12 when being excited with an AC voltage pulse received from the evaluation electronic circuits 14, 16 and converting the ultrasonic pulse into an AC voltage signal being transmitted to the electronic circuits 14, 16. The electronic circuits 14, 16 evaluate the receiving signal, monitors the filling level in the container 10 on the output side and detect a limit level. |
