Micro-machined accelerometer
First Claim
1. A transducer comprising,a movable mass supported by springs from a support structure;
- said mass having a surface with a sense conducting area and a force conducting area, said mass being free to move between corresponding first and second sense conducting areas and first and second force conducting areas on plates which face said surface of said mass and which are secured to said support structure, said sensing conducting areas and said force conducting areas being electrically isolated from each other;
means for applying a first voltage between said first and second sense conducting areas of said plates thereby creating a sense electric field between said sense conducting areas and inducing a sense voltage on said mass sense conducting area of said mass surface proportional to the displacement of said mass surface between said plates,means for applying a second voltage between said first and second force conducting areas of said plates thereby creating a force electric field between said force conducting areas,forward circuit means responsive to said sense voltage for generating a displacement signal representative of the distance said mass has moved from a reference position between said plates, andfeedback circuit means responsive to said displacement signal for applying an amount of electric charge proportional to the level of said displacement signal on said force conducting area of said mass surface such that a force is created on said mass proportional to the numerical product of said amount of charge and said force electric field in a direction to restore said mass to said reference position.
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Accused Products
Abstract
The transducer is fabricated using micro-machining techniques of a silicon wafer. The transducer includes E-shaped leaf springs of silicon dioxide suspending a mass from a support. The transducer is formed by chemical etching through openings of opposite faces of a silicon wafer on which etch stop layer patterns are diffused. Sense and force conductive patterns are diffused onto the opposite faces of the suspended mass. The spring-mass-support structure is then sandwiched between opposite plates having corresponding sense and force conductive patterns which face such patterns on the suspended mass. Circuitry is provided by which a sense voltage and a force voltage are applied between opposite sense and force conductive patterns of the opposite plates creating a sense electric field and a force electric field across the sense and force patterns of the mass. A feedback circuit arrangement is provided to maintain the mass at a predetermined reference position between the support plates. Forward circuitry of the feedback arrangement produces a displacement signal in response to a voltage induced on the sense area of the mass as it moves in response to acceleration applied to the support structure. The feedback arrangement produces an amount of charge in response to the displacement signal which is applied to the force conducting area of the mass. The force on the mass is proportional to the product of that charge and the force electric field intensity which causes the mass to remain close to a reference position between the plates.
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Citations
21 Claims
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1. A transducer comprising,
a movable mass supported by springs from a support structure; -
said mass having a surface with a sense conducting area and a force conducting area, said mass being free to move between corresponding first and second sense conducting areas and first and second force conducting areas on plates which face said surface of said mass and which are secured to said support structure, said sensing conducting areas and said force conducting areas being electrically isolated from each other; means for applying a first voltage between said first and second sense conducting areas of said plates thereby creating a sense electric field between said sense conducting areas and inducing a sense voltage on said mass sense conducting area of said mass surface proportional to the displacement of said mass surface between said plates, means for applying a second voltage between said first and second force conducting areas of said plates thereby creating a force electric field between said force conducting areas, forward circuit means responsive to said sense voltage for generating a displacement signal representative of the distance said mass has moved from a reference position between said plates, and feedback circuit means responsive to said displacement signal for applying an amount of electric charge proportional to the level of said displacement signal on said force conducting area of said mass surface such that a force is created on said mass proportional to the numerical product of said amount of charge and said force electric field in a direction to restore said mass to said reference position. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A transducer comprising,
a mass supported by springs from a support structure, said mass having a surface with a force conducting area, said mass being free to move between corresponding first and second force conducting areas on plates which face said force conducting area of said mass and which are secured to said support structure, sensing means for generating a displacement signal representative of displacement of said mass from a reference position with respect to said support structure, forward circuit means responsive to said displacement signal for converting said displacement signal to an output binary bit stream, said forward circuit means including binary sampler means for producing said output binary bit stream as a sequence of equal time length bi-level pulses representing "1"s and "0"s, feedback circuit means responsive to said output binary bit stream for applying bi-level electrostatic force pulses to said mass is synchronism with said "1"s and "0"s of said output binary bit stream and in a direction tending to restore said mass to said reference position, said force pulses characterized by having an approximately constant level during each time length of said bi-level pulses, said bi-level force pulses resulting from bi-level charge-electrostatic field forces applied between said force conducting area of said mass and said force conducting areas of said plates which face said force conducting area of said mass, whereby said output binary bit stream is representative of a characteristic of motion of said support structure.
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21. A transducer comprising,
a movable mass supported by springs from a support structure, sensing means for generating a sensing signal representative of displacement of said mass from a reference position with respect to said support structure, said mass having a surface with a force conducting area, said mass being free to move between first and second force conducting areas on plates which face said surface of said mass and which are secured to said support structure, means for applying a voltage between said first and second force conducting areas of said plates thereby creating a force electric field between said force conducting areas, forward circuit means responsive to said sensing signal for generating a displacement signal representative of the distance said mass has moved from a reference position between said plates, and feedback circuit means responsive to said displacement signal for applying an amount of electric charge on said force conducting area proportional to the amplitude of the displacement signal of said mass surface such that a force is created on said mass proportional to the numerical product of said amount of charge and said force electric field in a direction to restore said mass to said reference position.
Specification