Measuring and testing – Instrument proving or calibrating – Speed – velocity – or acceleration
Patent
1999-03-12
2000-03-14
Raevis, Robert
Measuring and testing
Instrument proving or calibrating
Speed, velocity, or acceleration
G01P 1500
Patent
active
060356944
ABSTRACT:
A method and apparatus for measuring and compensating for stray capacitance of a micro-machined sensor of an accelerometer system is disclosed. Stray capacitance differences between a top plate and a sensing element and between a bottom plate and the sensing element degrade accelerometer performance if not compensated for. Measurement of stray capacitance difference is achieved by operating the accelerometer in two calibration phases and measuring the steady-state output voltage in each of the two phases. In calibration phase 1, no force is applied to the sensor during clock intervals 1-4. In calibration phase 2, a dummy force up is applied and then a dummy force down is applied during those intervals 1-4. The difference in the output voltage of the two calibration phases is representative of the difference in stray capacitance of the sensor. Capacitance is added to the top or bottom plates in an amount proportional to the measured stray capacitance. The procedure is repeated until the voltage difference of the two calibration phases is zeroed, which is indicative that the inherent stray capacitance has been zeroed.
REFERENCES:
patent: 4381677 (1983-05-01), Ruesch et al.
patent: 5237285 (1993-08-01), Lofgren et al.
patent: 5600066 (1997-02-01), Torregrosa
patent: 5652384 (1997-07-01), Henrion et al.
Rick West, Automatic Calibration of Strain Gauges, Sensor Solutions, SENSORS Jul. 1995 pp. 44,46.
Abrams Michael L.
Burchfield Mark E.
Devolk Burton A.
Dupuie Scott T.
Johnson Richard A.
Bush Gary L.
I/O of Austin, Inc.
Raevis Robert
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