Patent ID: 6483322
Filing Date: 2002-11-19
Classification: G01P

Abstract:
A capacitive physical quantity sensor comprising:first and second variable capacitors, each including a movable electrode and a fixed electrode facing each other, capacitances of said first and second variable capacitors varying in accordance with a physical quantity on said movable electrodes; signal generation means for periodically supplying carrier signals to said fixed electrodes to measure variation in differential capacitance of said first and second variable capacitors at a first period in a measuring mode and at a second period in a self-diagnostic modes and generating a displacement signal for displacing said movable electrodes at said second period in said self-diagnostic mode; and a signal processing circuit including: a C-V conversion circuit for converting a charge signal indicative of said differential capacitance into a voltage signal; and a switched capacitor filter circuit for filtering said voltage signal to output a filtered voltage signal in response to a filter circuit clock signal, wherein said signal generation means further generates said filter circuit clock signal in said measuring and self-diagnostic modes at the same period, and said first period is different from said second period.