Accelerometer
First Claim
1. An accelerometer, comprising:
- a monocrystalline silicon wafer etched to form a fixed portion, a movable portion, and a resilient coupling between, the fixed and movable portions generally arranged in the plane of the wafer, the mass of the movable portion being concentrated on one side of the resilient coupling;
one of the fixed and moveable portions of the silicon structure including a first electrode oriented parallel to an axis of acceleration, the other of the fixed and moveable portions including a second electrode oriented parallel to the axis of acceleration, the other of the fixed and moveable portions bearing a metal layer mechanically coupled with the second electrode and electrically connected as a third electrode coplanar with the second electrode, the second and third electrodes being stacked in a direction parallel to the axis of acceleration and arranged in capacitive opposition to the first electrode;
a resilient coupling designed to retain the first and third electrodes in capacitive opposition to each other across a capacitance gap while allowing motion of the first electrode relative to the second and third electrodes in response to acceleration along an axis of acceleration perpendicular to the plane of the wafer, and to resiliently restore the first electrode to an equilibrium position relative to the second and third electrodes when the acceleration ceases, the second electrode being in opposition to a majority of the surface area of the first electrode when the electrodes are in the equilibrium position, the capacitance gap being oriented parallel to the axis of acceleration, the capacitance between the first electrode and third electrode increasing as the movable portion moves away from the equilibrium position in a direction along the axis of acceleration and decreasing as the movable portion moves in an opposite direction away from the equilibrium position; and
electronics and/or software designed to translate a measurement of capacitance between the first and third electrodes into a measurement of acceleration along the axis.
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Accused Products
Abstract
An accelerometer. A silicon wafer is etched to form a fixed portion, a movable portion, and a resilient coupling between, the fixed and movable portions generally arranged in the plane of the wafer, the mass of the movable portion being concentrated on one side of the resilient coupling. One of the fixed and moveable portions of the silicon structure includes a first electrode. The other of the fixed and moveable portions includes a second electrode oriented parallel to the axis of acceleration, and an electrically-conductive layer electrically connected as a third electrode coplanar and mechanically coupled with the second electrode. The second and third electrodes are arranged in capacitive opposition to the first electrode, the capacitance between the first electrode and third electrode increasing as the movable portion moves in a direction along the axis of acceleration relative to the fixed portion and decreasing as the movable portion moves in an opposite direction. A resilient coupling retains the first and third electrodes in capacitive opposition to each other across a capacitance gap while allowing motion of the first electrode relative to the second and third electrodes in response to acceleration along an axis of acceleration perpendicular to the plane of the wafer, and resiliently restores the first electrode to an equilibrium position when the acceleration ceases. The second electrode is in opposition to a majority of the surface area of the first electrode when the electrodes are in the equilibrium position. Capacitance between the first and third electrodes is measured to obtain a measurement of acceleration along the axis.
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Citations
66 Claims
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1. An accelerometer, comprising:
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a monocrystalline silicon wafer etched to form a fixed portion, a movable portion, and a resilient coupling between, the fixed and movable portions generally arranged in the plane of the wafer, the mass of the movable portion being concentrated on one side of the resilient coupling;
one of the fixed and moveable portions of the silicon structure including a first electrode oriented parallel to an axis of acceleration, the other of the fixed and moveable portions including a second electrode oriented parallel to the axis of acceleration, the other of the fixed and moveable portions bearing a metal layer mechanically coupled with the second electrode and electrically connected as a third electrode coplanar with the second electrode, the second and third electrodes being stacked in a direction parallel to the axis of acceleration and arranged in capacitive opposition to the first electrode;
a resilient coupling designed to retain the first and third electrodes in capacitive opposition to each other across a capacitance gap while allowing motion of the first electrode relative to the second and third electrodes in response to acceleration along an axis of acceleration perpendicular to the plane of the wafer, and to resiliently restore the first electrode to an equilibrium position relative to the second and third electrodes when the acceleration ceases, the second electrode being in opposition to a majority of the surface area of the first electrode when the electrodes are in the equilibrium position, the capacitance gap being oriented parallel to the axis of acceleration, the capacitance between the first electrode and third electrode increasing as the movable portion moves away from the equilibrium position in a direction along the axis of acceleration and decreasing as the movable portion moves in an opposite direction away from the equilibrium position; and
electronics and/or software designed to translate a measurement of capacitance between the first and third electrodes into a measurement of acceleration along the axis.
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2. An accelerometer, comprising:
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a fixed structure and a movable structure, the fixed and movable structures generally arranged in a plane, the fixed structure bearing a fixed electrode, the movable structure bearing a movable electrode;
a resilient coupling designed to retain the fixed and movable structures in capacitive opposition to each other across a capacitance gap while allowing motion of the movable electrode relative to the fixed electrode in response to acceleration along an axis of acceleration perpendicular to the plane, and to resiliently restore the two electrodes to an equilibrium position when the acceleration ceases; and
electronics and/or software designed to translate a measurement of capacitance between the fixed and movable electrodes into a measurement of the acceleration along the axis. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A method, comprising the steps of:
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applying an acceleration to a fixed structure and a movable structure, the fixed and movable structures generally arranged in a plane perpendicular to an axis of the acceleration, the fixed structure bearing a fixed electrode, the movable structure bearing a movable electrode;
in response to the acceleration, allowing motion of the movable electrode relative to the fixed electrode, a resilient coupling retaining the fixed and movable structures in capacitive opposition to each other across a capacitance gap;
resiliently restoring the two electrodes to an equilibrium position when the acceleration ceases; and
measuring capacitance between the movable and fixed electrodes, and translating the measured capacitance into an expression of the acceleration. - View Dependent Claims (19, 20, 21)
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22. An accelerometer, comprising:
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a fixed portion and a movable portion, the fixed and movable portions generally arranged in a plane;
a resilient coupling designed to allow motion of the movable portion relative to the fixed portion in response to acceleration along an axis of acceleration perpendicular to the plane and to resiliently restore the two portions to an equilibrium position when the acceleration ceases;
one of the fixed and moveable portions being electrically connected as a first electrode, the other of the fixed and moveable portions bearing an electrically-conductive layer electrically connected as a second electrode, the first and second electrodes being arranged in capacitive opposition to each other;
electronics and/or software designed to translate a measurement of capacitance between the first and second electrodes into a measurement of acceleration along the axis. - View Dependent Claims (23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
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34. A method, comprising the steps of:
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establishing an electric field between a movable electrode and a fixed electrode of an accelerometer, the movable and fixed electrodes being arranged in capacitive opposition to each other, one of the fixed and moveable electrodes being formed of silicon, the other of the fixed and moveable electrodes being formed as an electrically-conductive layer mechanically coupled with and electrically isolated from a silicon structure and stacked with the silicon structure in a direction of an axis of acceleration, the silicon structure being generally coplanar with the electrode formed of silicon;
allowing motion of movable electrode relative to the fixed electrode in response to an acceleration along the axis of acceleration, and allowing a resilient coupling to restore the two electrodes to an equilibrium position when the acceleration ceases;
measuring capacitance between the movable and fixed electrodes, and translating the measured capacitance into an expression of the acceleration. - View Dependent Claims (35, 36, 37)
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38. An accelerometer, comprising:
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a silicon wafer etched to form a fixed portion, a movable portion, and a resilient coupling between, the fixed and movable portions generally arranged in a plane, the resilient coupling designed to allow motion of movable portion relative to the fixed portion perpendicular to the wafer in response to acceleration perpendicular to the wafer and to resiliently restore the two portions to an equilibrium position when the acceleration ceases, the mass of the movable portion being concentrated on one side of the resilient coupling;
the fixed and moveable portions each bearing an electrode, the electrodes being arranged in capacitive opposition; and
electronics and/or software designed to translate a measurement of capacitance between the first and second electrodes into a measurement of acceleration perpendicular to the wafer. - View Dependent Claims (39, 40, 41, 42, 43, 44, 45, 46, 47)
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48. A method of detecting acceleration along an axis of acceleration, comprising the steps of:
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establishing an electric field between a movable electrode and a fixed electrode of an accelerometer, the movable and fixed electrodes being arranged in capacitive opposition to each other and being mechanically borne on movable and fixed portions, respectively, of a structure etched from a silicon wafer, the fixed and movable portions generally arranged in a plane, allowing motion perpendicular to the wafer of the movable electrode relative to the fixed electrode in response to an acceleration perpendicular to the wafer, and allowing a resilient coupling to restore the two electrodes to an equilibrium position when the acceleration ceases, the mass of the movable portion being concentrated on one side of the resilient coupling; and
measuring capacitance between the movable and fixed electrodes, and translating the measured capacitance into an expression of the acceleration. - View Dependent Claims (49, 50, 51)
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52. An accelerometer, comprising:
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first, second and third electrodes, the second electrode being coplanar with the third electrode, the second and third electrodes being arranged in capacitive opposition to the first electrode across a capacitance gap;
a resilient coupling designed to allow motion of the first electrode relative to the second and third electrodes along the axis of acceleration in response to acceleration and to resiliently restore the first electrode to an equilibrium position when the acceleration ceases, the second electrode being in opposition to a majority of the surface area of the first electrode when the electrodes are in the equilibrium position; and
electronics and/or software designed to translate a measurement of capacitance between the first and third electrodes into a measurement of acceleration along the axis. - View Dependent Claims (53, 54, 55, 56, 57, 58, 59)
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60. A method, comprising the steps of:
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establishing an electric field between first, second and third electrodes of an accelerometer, the second and third electrodes being arranged in capacitive opposition to the first electrode, the first, second and third electrodes being mechanically borne on movable and fixed portions of an accelerometer, the second and third electrodes being mechanically coupled and generally coplanar with each other;
allowing motion, perpendicular to the plane generally containing the second and third electrodes, of the movable portion relative to the fixed portion in response to an acceleration, and allowing a resilient coupling to restore the electrodes to an equilibrium position when the acceleration ceases, the second electrode being in opposition to a majority of the surface area of the first electrode when the electrodes are in the equilibrium position; and
measuring capacitance between the first and third electrodes, and translating the measured capacitance into an expression of the acceleration. - View Dependent Claims (61, 62, 63, 64, 65, 66)
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Specification