Multiple axis acceleration sensor
First Claim
1. Apparatus comprising:
- an acceleration sensor having a plurality of sensing elements oriented in a device plane, the sensing elements including at least one fixed sensing electrode and a mass suspended so as to be movable relative to the at least one fixed sensing electrode along at least one axis in the device plane and along an axis normal to the device plane; and
a controller operably coupled to sense movement of the mass along at least one axis in the device plane and along the axis normal to the device plane, the controller sensing movement of the mass within the device plane using at least one capacitor having a plate formed from at least one fixed sensing electrode and a plate formed by a surface that moves with the mass, the controller sensing movement of the mass along the axis normal to the device plane using a measurement capacitor and a reference capacitor, the measurement capacitor having a plate formed by the mass and a plate formed by an underlying conducting plane, the reference capacitor having a plate formed from at least one fixed sensing electrode used for sensing movement of the mass within the device plane and a plate formed by the underlying conducting plane.
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Accused Products
Abstract
One or more fixed sensing electrodes are employed to sense movement of a mass both within the plane of the mass/electrodes and along an axis normal to that plane. In order to measure movement of the mass along the axis normal to the plane, a reference capacitance is measured between the fixed sensing electrode(s) and an underlying conducting plane and a measurement capacitance is measured between the mass and the underlying conducting plane. A value Cv-KCf may be computed, where Cf is the reference capacitance, Cv is the measurement capacitance, and K is a predetermined constant. In accordance with certain embodiments of the invention, a standard one or two axis acceleration sensor that measures movement of the mass within the plane can be used to also measure movement of the mass in the axis normal to the plane.
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Citations
21 Claims
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1. Apparatus comprising:
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an acceleration sensor having a plurality of sensing elements oriented in a device plane, the sensing elements including at least one fixed sensing electrode and a mass suspended so as to be movable relative to the at least one fixed sensing electrode along at least one axis in the device plane and along an axis normal to the device plane; and
a controller operably coupled to sense movement of the mass along at least one axis in the device plane and along the axis normal to the device plane, the controller sensing movement of the mass within the device plane using at least one capacitor having a plate formed from at least one fixed sensing electrode and a plate formed by a surface that moves with the mass, the controller sensing movement of the mass along the axis normal to the device plane using a measurement capacitor and a reference capacitor, the measurement capacitor having a plate formed by the mass and a plate formed by an underlying conducting plane, the reference capacitor having a plate formed from at least one fixed sensing electrode used for sensing movement of the mass within the device plane and a plate formed by the underlying conducting plane. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. In an acceleration sensing apparatus having a plurality of sensing elements oriented in a device plane, the sensing elements including at least one fixed sensing electrode and a mass suspended so as to be movable relative to the at least one fixed sensing electrode along at least one axis in the device plane and along an axis normal to the device plane, a method for sensing acceleration, the method comprising:
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sensing movement of the mass along at least one axis in the device plane using at least one capacitor having a plate formed from at least one fixed sensing electrode and a plate formed by a surface that moves with the mass; and
sensing movement of the mass along the axis normal to the device plane using a measurement capacitor and a reference capacitor, the measurement capacitor having a plate formed by the mass and a plate formed by an underlying conducting plane, the reference capacitor having a plate formed from at least one fixed sensing electrode used for sensing movement of the mass within the device plane and a plate formed by the underlying conducting plane. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. Apparatus for use with an acceleration sensor having a plurality of sensing elements oriented in a device plane, the sensing elements including at least one fixed sensing electrode and a mass suspended so as to be movable relative to the at least one fixed sensing electrode along at least one axis in the device plane and along an axis normal to the device plane, the apparatus comprising:
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means for sensing movement of the mass along at least one axis in the device plane using at least one capacitor having a plate formed from at least one fixed sensing electrode and a plate formed by a surface that moves with the mass; and
means for sensing movement of the mass along an axis normal to the device plane using a measurement capacitor and a reference capacitor, the measurement capacitor having a plate formed by the mass and a plate formed by an underlying conducting plane, the reference capacitor having a plate formed from at least one fixed sensing electrode used for sensing movement of the mass within the device plane and a plate formed by the underlying conducting plane.
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Specification