Patent ID: 6792805
Filing Date: 2004-09-21
Classification: G01P

Abstract:
A capacitive acceleration sensor comprising:a supporting substrate; a movable member, which is located above a surface of the supporting substrate, wherein the movable member is supported by the supporting substrate to move with respect to the supporting substrate along predetermined directions parallel to the surface in response to a force that acts on the movable member along the predetermined directions; a first fixed member; a second fixed member, wherein each fixed member is located above the surface of the supporting substrate, wherein each fixed member is supported by the supporting substrate to be stationary with respect to the supporting substrate under the force, wherein a first capacitance is formed between the movable member and the first fixed member and a second capacitance is formed between the movable member and the second fixed member, wherein one of the capacitances increases while the other capacitance decreases when the movable member moves in response to the force, wherein the force includes a substantially constant force and a variable force when an acceleration is measured using the sensor, wherein the variable force is proportional to the acceleration, wherein the acceleration is measured on a basis of a difference in quantity between the capacitances, wherein the capacitances are different in quantity from each other when the force that acts on the movable member is zero to reduce a difference in quantity between the capacitances that corresponds to the substantially constant force, wherein during operation in a mounted state, the movable member is vertical to or at a slant with respect to ground, and a first electrode clearance between the first fixed member and the movable member is substantially equal to a second electrode clearance between the second fixed member and the movable member, and wherein during non-operation in a non-mounted state, the first electrode clearance is different than the second electrode clearance.