초록 ▼

A capacitive physical-quantity detection apparatus includes a movable electrode (2d) which is displaced in response to a physical quantity. A fixed electrode (3, 4) opposed to the movable electrode forms a capacitor in conjunction with the movable electrode. A signal applying device (23, 24) operate

A capacitive physical-quantity detection apparatus includes a movable electrode (2d) which is displaced in response to a physical quantity. A fixed electrode (3, 4) opposed to the movable electrode forms a capacitor in conjunction with the movable electrode. A signal applying device (23, 24) operates for applying a first signal between the movable electrode and the fixed electrode. The first signal is periodic, and has at least a first time period for detection of a capacity variation and a second time period for displacement of the movable electrode to implement self diagnosis. A C-V conversion circuit (21) operates for generating a voltage which depends on a variation in a capacitance of the capacitor during the first time period. A signal processing circuit (22) operates for processing the voltage generated by the C-V conversion circuit into a second signal depending on the physical quantity. A changing device (23) operates for changing the first signal in the second time period between a state for execution of self diagnosis and a state for unexecution of self diagnosis. The first signal in the state for execution of self diagnosis applies a pseudo physical quantity to the movable electrode.

대표청구항 ▼

[ What is claimed is:] [1.]1. A capacitive physical-quantity detection apparatus comprising:a movable electrode which is displaced in response to a physical quantity;a fixed electrode opposed to the movable electrode to form a capacitor in conjunction with the movable electrode;signal applying means

[ What is claimed is:] [1.]1. A capacitive physical-quantity detection apparatus comprising:a movable electrode which is displaced in response to a physical quantity;a fixed electrode opposed to the movable electrode to form a capacitor in conjunction with the movable electrode;signal applying means for applying a first signal between the movable electrode and the fixed electrode, the first signal being periodic and having at least a first time period corresponding to a normal-operation time period for detection of a capacity variation and a second time period for displacement of the movable electrode to implement self diagnosis;a C-V conversion circuit for generating a voltage which depends on a variation in a capacitance of the capacitor during the first time period the C-V conversion circuit including a switch for discharging the capacitor to implement a resetting process;a signal processing circuit for processing the voltage generated by the C-V conversion circuit into a second signal depending on the physical quantity; andchanging means for changing the first signal in the second time period between a state for execution of self diagnosis and a state for unexecution of self diagnosis;wherein the first signal in the state for execution of self diagnosis applies a pseudo physical quantity to the movable electrode, and the changing means includes means for changing a potential at the movable electrode, and wherein the signal applying means includes means for, during execution of self diagnosis, subjecting the fixed electrode to a potential equal to that applied to the fixed electrode for the normal-operation time period.