Patent ID: 7392706

Claim:
A pressure sensor device comprising: a supporting substrate; a sensor substrate made of a piezoelectric material, having a lower surface on which a sensor section for detecting pressure is formed; a concave portion formed on the upper surface of the sensor substrate; and a sealing member that is joined to an upper surface of the supporting substrate and the lower surface of the sensor substrate and forms a sealing space for sealing the sensor section between the substrates, the sensor section being provided with a first surface acoustic wave element for detecting pressure by forming an IDT electrode on the lower surface of the sensor substrate within a region where the concave portion is formed at a plan view, and with a second surface acoustic wave element for reference for comparing output signals of the first surface acoustic wave element and the second surface acoustic wave element on the lower surface of the sensor substrate positioned in a region out of the concave portion at a plan view, wherein a frequency band from a resonance frequency to an antiresonance frequency of the first surface acoustic wave element and a frequency band from a resonance frequency to an antiresonance frequency of the second surface acoustic wave element do not overlap each other, and further comprising: a first oscillating circuit that oscillates at a predetermined frequency based on the resonance frequency of the first surface acoustic wave element or based on delay time of an electrical signal generated by the first surface acoustic wave element; a second oscillating circuit that oscillates at a predetermined frequency based on the resonance frequency of the second surface acoustic wave element based on delay time of an electrical signal generated by the second surface acoustic wave element; a difference generating circuit that generates and outputs a conversion signal by comparing an oscillation signal from the first oscillating circuit with an oscillation signal from the second oscillating circuit; and a modulation circuit that modulates the conversion signal from the difference generating circuit and the oscillation signal from the second oscillating circuit and outputs these to the outside.