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Accelerometer

  • US 20030106372A1
  • Filed: 10/19/2001
  • Published: 06/12/2003
  • Est. Priority Date: 10/19/2001
  • Status: Active Grant
First Claim
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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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