Method for calibrating accelerometer sensitivity
First Claim
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1. A method of calibrating an accelerometer comprising:
- a. providing the accelerometer comprising;
i. a substrate;
ii. a mass suspended over the substrate and movable relative to the substrate, the mass including a movable electrode;
iii. a first fixed electrode suspended over the substrate and not movable relative to the substrate;
iv. a second fixed electrode suspended over the substrate and not movable relative to the substrate, the movable electrode and the first and second fixed electrode forming a differential capacitor;
v. an excitation and readout circuit coupled to the movable electrode and to the fixed electrodes to provide an amplified signal;
vi. an actuator, the actuator suspended over the substrate, the actuator displacing the mass by electrical means when activated; and
vii. a spring suspended over the substrate connected to the mass, the spring and the actuator laid out such that a dimensional relationship is established between the actuator and the spring;
b. measuring the resonant frequency of the mass;
c. displacing the mass with the actuator;
d. measuring the change in the amplified signal; and
e. calculating the sensitivity of the accelerometer.
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Abstract
A method for calibrating the sensitivity of a micromachined differential-capacitor accelerometer without applying mechanical stimulation, such as shaking. The accelerometer is fabricated with dimensional control structures so that a dimensional relationship is set-up among operational features of the device. The method includes measuring the resonant frequency of a movable mass and measuring the change in the output signal of the accelerometer as the mass is displaced by electrostatic means. The sensitivity of the accelerometer is then calculated.
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Citations
19 Claims
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1. A method of calibrating an accelerometer comprising:
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a. providing the accelerometer comprising;
i. a substrate;
ii. a mass suspended over the substrate and movable relative to the substrate, the mass including a movable electrode;
iii. a first fixed electrode suspended over the substrate and not movable relative to the substrate;
iv. a second fixed electrode suspended over the substrate and not movable relative to the substrate, the movable electrode and the first and second fixed electrode forming a differential capacitor;
v. an excitation and readout circuit coupled to the movable electrode and to the fixed electrodes to provide an amplified signal;
vi. an actuator, the actuator suspended over the substrate, the actuator displacing the mass by electrical means when activated; and
vii. a spring suspended over the substrate connected to the mass, the spring and the actuator laid out such that a dimensional relationship is established between the actuator and the spring;
b. measuring the resonant frequency of the mass;
c. displacing the mass with the actuator;
d. measuring the change in the amplified signal; and
e. calculating the sensitivity of the accelerometer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A self-calibrating accelerometer comprising:
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a. a substrate;
b. a mass suspended over the substrate and laterally movable relative to the substrate, the mass including a movable electrode;
c. a first fixed electrode suspended over the substrate and not movable relative to the substrate;
d. a second fixed electrode suspended over the substrate and not movable relative to the substrate, the movable electrode and the first and second fixed electrode forming a differential capacitor;
e. an excitation and readout circuit coupled to the movable electrode and to the fixed electrodes to provide an amplified signal;
f. an actuator, the actuator suspended over the substrate, the actuator displacing the mass by electrical means when activated; and
g. a spring suspended over the substrate connected to the mass, the spring and the actuator laid out such that a dimensional relationship is established between the actuator and the spring;
h. logic for i. measuring the resonant frequency of the mass, ii. displacing the mass with the actuator, iii. measuring the change in the amplified signal, and iv. calculating the sensitivity of the accelerometer. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18, 19)
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Specification