Patent ID: 7412887

Claim:
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.