Patent ID: 6450029
Filing Date: 2002-09-17
Classification: G01P

Abstract:
A capacitive physical quantity detection device comprising:a spring portion deformable upon application of a physical quantity in a specified direction to thereby have a spring function; a movable electrode integrally formed with the spring portion and deformable along with the spring portion in a deformation direction of the spring portion; a fixed electrode disposed opposing the movable electrode; signal application means connected to the movable portion and the fixed portion, for selectively applying between the movable electrode and the fixed electrode any one of periodically changeable signals including a detection signal for detection of the physical quantity and a self-diagnosis signal for use in performing self-diagnosis; and a C-V conversion circuit for generating an output voltage pursuant to a change in a capacitive element defined between the movable electrode and the fixed electrode, wherein the capacitive element is changeable in capacitance during application of the detection signal to thereby permit detection of the physical quantity; the spring portion is deformable upon application of the self-diagnosis signal to permit creation of a quasi-physical quantity at the movable electrode; and a ratio of a frequency of the self-diagnosis signal to a resonance frequency of the spring portion in its deformation direction is set so that a resonance magnification of the spring portion is more than or equal to one time upon applying of the self-diagnosis signal.