Method and unit for sensing physical quantity using capacitive sensor
First Claim
1. A method of sensing physical quantity using a capacitive sensor equipped with a first fixed electrode and a second fixed electrode disposed face to face and a movable electrode disposed between the first and second fixed electrodes so as to form variable first and second capacitors whose capacitances vary in response to the physical quantity sensed by the movable electrode, comprising:
- first adjusting a first bias voltage applied between the first fixed electrode and the movable electrode and a second voltage applied between the movable electrode and the second fixed electrode respectively to allow the movable electrode to be brought into contact with either of the first and second fixed electrodes;
second adjusting the first and second bias voltages to allow the movable electrode to return to a non-contact original position thereof between the first and second fixed electrodes, the second bias voltage adjustment performed by the second adjusting means following the first bias voltage adjustment performed by the first adjusting means; and
detecting, for self-diagnosis of the unit, an output signal corresponding to a relationship of capacitances between the first and second capacitors.
1 Assignment
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Accused Products
Abstract
A physical quantity (e.g., acceleration) sensing unit is provided. In this unit, a capacitive sensor has first and second fixed electrodes and a physical-quantity-sensitive movable electrode disposed between the first and second fixed electrodes. An adjusting circuit first adjusts a first bias voltage applied between the first fixed electrode and the movable electrode and a second voltage applied between the movable electrode and the second fixed electrode so that the movable electrode is brought into contact with either the first or second fixed electrode. The adjusting circuit then adjusts the first and second bias voltages to return the movable electrode to its original position. A detecting circuit detects an output on a capacitance relationship among the first and second fixed electrodes and the movable electrode. The output is subjected to determination of whether or not the output is out of order, when tested.
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Citations
18 Claims
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1. A method of sensing physical quantity using a capacitive sensor equipped with a first fixed electrode and a second fixed electrode disposed face to face and a movable electrode disposed between the first and second fixed electrodes so as to form variable first and second capacitors whose capacitances vary in response to the physical quantity sensed by the movable electrode, comprising:
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first adjusting a first bias voltage applied between the first fixed electrode and the movable electrode and a second voltage applied between the movable electrode and the second fixed electrode respectively to allow the movable electrode to be brought into contact with either of the first and second fixed electrodes; second adjusting the first and second bias voltages to allow the movable electrode to return to a non-contact original position thereof between the first and second fixed electrodes, the second bias voltage adjustment performed by the second adjusting means following the first bias voltage adjustment performed by the first adjusting means; and detecting, for self-diagnosis of the unit, an output signal corresponding to a relationship of capacitances between the first and second capacitors. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A unit for sensing physical quantity comprising:
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a capacitive sensor equipped with a first fixed electrode and a second fixed electrode disposed face to face and a movable electrode disposed between the first and second fixed electrodes so as to form variable first and second capacitors whose capacitances vary in response to a physical quantity sensed by the movable electrode; an adjusting circuit adjusting, in a first step, a first bias voltage applied between the first fixed electrode and the movable electrode and a second bias voltage applied between the movable electrode and the second fixed electrode respectively to allow the movable electrode to be brought into contact with either of the first and second fixed electrodes, and adjusting, in a second step, the first and second bias voltages to allow the movable electrode to return to non-contact original position thereof between the first and second fixed electrodes, the second step following the first step; and a detecting circuit detecting, for self-diagnosis of the unit, an output signal corresponding to a relationship of capacitances between the first and second capacitors. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16)
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17. A unit for sensing physical quantity comprising:
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a capacitive sensor equipped with a first fixed electrode and a second fixed electrode disposed face to face and a movable electrode disposed between the first and second fixed electrodes so as to form variable first and second capacitors whose capacitances vary in response to a physical quantity sensed by the movable electrode; first adjusting means for adjusting a first bias voltage applied between the first fixed electrode and the movable electrode and a second bias voltage applied between the movable electrode and the second fixed electrode respectively to allow the movable electrode to be brought into contact with either of the first and second fixed electrodes; second adjusting means for adjusting the first and second bias voltages to allow the movable electrode to return to non-contact original position thereof between the first and second fixed electrodes, the second bias voltage adjustment performed by the second adjusting means following the first bias voltage adjustment performed by the first adjusting means; and means for detecting, for self-diagnosis of the unit, an output signal corresponding to a relationship of capacitances between the first and second capacitors.
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18. An on-vehicle airbag system comprising:
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an airbag unit mounted on a vehicle and formed to have an airbag; a physical quantity sensing unit sensing a physical quantity as a signal indicative of the sensed physical quantity; and a controller controlling a development of the airbag in response to the signal outputted by the sensing unit, wherein the physical quantity sensing unit comprises; a capacitive sensor equipped with a first fixed electrode and a second fixed electrode disposed face to face and a movable electrode disposed between the first and second fixed electrodes so as to form variable first and second capacitors whose capacitances vary in response to a physical quantity sensed by the movable electrode; an adjusting circuit adjusting, in a first step, a first bias voltage applied between the first fixed electrode and the movable electrode and a second bias voltage applied between the movable electrode and the second fixed electrode respectively to allow the movable electrode to be brought into contact with either of the first and second fixed electrodes, and adjusting, in a second step, the first and second bias voltages to allow the movable electrode to return to a non-contact original position thereof between the first and second fixed electrodes, the second step following the first step; a detecting circuit detecting, for self-diagnosis of the unit, an output signal corresponding to a relationship of capacitances between the first and second capacitors; and a determining unit determining whether or not the output signal detected by the detecting circuit is out of order, as the self-diagnosis of the unit.
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Specification