Patent ID: 6792804
Filing Date: 2004-09-21
Classification: G01P

Abstract:
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; one of the fixed and moveable portions including a first electrode, the other of the fixed cod moveable portions including a second electrode, the other of the fixed and moveable portions comprising an electrically conductive layer mechanically coupled with the second electrode and electrically connected as a third electrode, the second and third electrodes being stacked ins direction parallel to an 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 first and second electrodes being arranged in direct capacitive opposition and the first and third electrodes being arranged in indirect capacitive opposition, 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 of acceleration.