Input/output, Inc.

I/o Sensors, Inc.

I/o of Austin, Inc.

Ion Geophysical Corporation

Burton A Devolk

Richard A Johnson

Ben William Jones

Scott T Dupuie

Mark E Burchfield

Michael L Abrams

Roger Maher

Franklin W Mayo

Matthew W Ip

Jeffrey Blackburn

Mauricio A Zavaleta

Raymond K Erickson

Mauricio Zavaleta

Frank Mayo

James Broseghini

Bing F Fung

Ben Jones

Jeffrey A Blackburn

A system for acquiring environmental information measurements. The 5 system () utilize a sensor, () a front-end circuit, () a loop filter (), a switch controller (), and a reduced-order loop control circuit to provide reliable data measurements while providing robust system behavior. The system further includes a sensor simulator () for simulating the operation of the sensor () and testing the operation of the front-end circuit () and the loop filter ().

Sensor

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.

Method and apparatus for calibration of stray capacitance mismatch in a

Apparatus for measuring a characteristic of motion and methods for its manufacture are disclosed in which a sensor structure includes a support structure, and a mass suspended from such support structure by a spring connecting arrangement and electrical devices for measuring displacement of the mass which results from a force applied to the support structure. An apparatus is provided where the mechanical spring constant of the connecting arrangement of the sensor structure is provided to be a high value representative of a strong, stiff spring which resists breaking due to high forces applied to it, and where an electric spring constant is provided to yield a small effective sensor spring constant K.sub.eff =K.sub.m -K.sub.e. Methods are also provided to manufacturing the apparatus by specifying the mechanical spring constant and providing an electric spring constant which will yield a desired effective spring constant which produces a desired characteristic of the sensor structure. Alternatively, the apparatus may be manufactured by specifying the electric spring constant which, with a mechanical spring constant, provides a certain sensor structure characteristic, e.g., natural frequency, and then providing a connecting arrangement characterized by a mechanical spring constant which yields such sensor characteristic. According to another aspect of the invention, the sensing force applied to the mass is adjusted in coordination with the mechanical spring constant and damping factor of the apparatus so that a desired characteristic of the apparatus is achieved.

Apparatus with mechanical and electric springs and method for its

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Cedar Park, TX, United States of America

Burton A Devolk