PURPOSE: To surely detect the breakage of a plate by electrically contacting a piezoelectric force sensor with at least an electrode on one side via one or more conducting passages, which are provided on a piezoelectric plate, and breaking the conducting passage when the plate is broken.
CONSTITUTION: The piezoelectric plate 1 consisting of two plate half parts 2, 3 is fixed to a carrying body 8 on its lower surface via a supporting body 7. An electrode 5 is installed in the entire surface of the lower surface of the plate 1, while a patterned electrode 4 is installed in the upper surface. The electrode 4 is brought electrically into contact with a connecting wire 6 fixed to a start area 12, while the area 12 is connected to the electrode 4 by means of a conducting passage 20. The electrode 5 is electrically connected with a conductive supporting body 7 by means of other conducting passage installed in the carrying body 8. When the sensor is used as an acceleration sensor, since the acceleration in the direction perpendicular to the surface of the carrying body 8 is produced so that a moving area 11, which is not supported by the supporting body 7, moves, a mechanical load is applied to a bent wire 10. When the plate 1 is broken in an around the bent wire 10, the conducting passage 20 is broken. As a result, the capacity of the plate 1, which is measured via the conducting passage 20 varies. Thus, the breakage of the plate 1 can be detected.
BOOTO TSUIIGENBAIN
BERUNTO MAIHEEFUAA
