Patent ID: 7337669

Claim:
An inertial sensor, comprising: a detecting element which includes a first capacitor portion that is made up of a first detection electrode provided in a fixed portion and a first movable electrode provided in a movable portion, and a second capacitor portion that is made up of a second detection electrode provided in the fixed portion and a second movable electrode provided in the movable portion; a drive circuit operable to apply an AC-bias signal voltage to the first and second movable electrode electrodes; a detection circuit which includes: a differential-type detector operable to detect a difference in a quantity of an electric charge between the first and second detection electrodes, wherein the first and second movable electrodes are displaced according to an acceleration which is applied to the detecting element, and wherein a quantity of an electric charge which is generated in the second detection electrode decreases when a quantity of an electric charge which is generated in the first detection electrode increases, and conversely, the quantity of an electric charge which is generated in the second detection electrode increases when the quantity of an electric charge which is generated in the first detection electrode decreases; a synchronous demodulator operable to demodulate an output signal of the differential-type detector synchronously with the AC-bias signal voltage; and an output amplifier operable to regulate an output signal from the synchronous demodulator; and a self-diagnosis circuit operable to apply the AC-bias signal voltage ahead of the synchronous demodulator, and to output a diagnostic signal indicating whether there is an abnormality in at least one of the detecting element and the detection circuit.