| 摘要 |
PURPOSE:To improve reliability by imparting preliminary stress in the axial direction of a piezoelectric element, dividing a center cabinet into a sensing part and an attaching screw part for attaching the sensing part to a body under test, and fixing the sensing part to the attaching screw part. CONSTITUTION:A sensing part 12 is fixed to an attaching screw part 11 through a sealing material 17 only at a contact surface 11a by the tightening force of a fixing screw. A pressure receiving surface 13 is provided in a region to be measured. A pressure transmission member 14 is in contact with the inside of the pressure receiving surface 13. A piezoelectric element 15 is provided at the opposite side of the member 14 with respect to the pressure receiving surface 13. The element 15 and the member 14 are pushed to the pressure receiving surface by the tightening force of an upper fixing screw 16. Thus, preliminary stress is applied on the element 15. The pressure which is applied on the pressure receiving surface 13 by the fluctuation in pressure generated in the region to be measured is transmitted to the element 15 through the member 14. Since the outer surface of the element 15 is fixed with the screw 16, shearing stress is generated in the inside of the element 15. The electric charge corresponding to the shearing stress is generated in the element 15. Since the preliminary stress of the element 15 is not fluctuated, the fluctuation in output of a sensor can be removed.
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