| 摘要 |
PROBLEM TO BE SOLVED: To detect pressure levels in a simple constitution by oscillating one end of plane- shaped pizoelectrics by an oscillation generating means, detecting the oscillation characteristics of the piezoelectrics which change in response to pressure when the piezoelectrics are applied with pressure by an oscillation detecting means, and computing the pressure on the basis of an output signal by a pressure computing means. SOLUTION: In an oscillation generating means 12, the part of the plane-shaped piezoelectrics 11a sandwiched by electrodes 12a and 12b is oscillated in response to an oscillation signal generated at a signal generating part 14. This oscillation is propagated to an oscillation detecting means 13 and an oscillation characteristics control means 16 via the part of the high-molecular piezoelectrics 11b to oscillate the overall plane-shaped piezoelectrics 11 with certain characteristics. A detection voltage is generated at the detecting means 13 in response to the oscillation. The oscillation of the overall piezoelectrics 11 also largely depends on the frequency of an oscillation signal. The frequency at which the detection voltage detected at the detecting means 13 first shows a local maximum is defined as the first resonance frequency. When the piezoelectrics 11 are applied with pressure or weight, the first resonance frequency is approximately determined dependently on the length L of the piezoelectrics 11 and the velocity of sound, and the distortion and stress of the piezoelectrics 11 become maximum at its center.
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