Texas Instruments Corporation

Sensata Technologies, Inc.

John A Powning

Keith W Kawate

Thomas Richard Maher

Mark Genovese

Eric Visser

An improved system and method of performing capacitance measurements that provides a fast digital response and a reduced output error. The capacitance measurement system includes a circuit configuration that has a variable capacitor and at least one reference capacitor connected to one another at a common node, which in turn is connected to the input of an analog-to-digital converter. The circuit configuration further includes an array of switches coupled between the variable and reference capacitors and the supply voltage, a reference voltage, and ground, respectively. The switched variable and reference capacitors are employed in conjunction with the A-to-D converter to perform, at the common node, a plurality of direct voltage measurements for use in generating an expression defining the capacitance of the variable capacitor.

Microprocessor-based capacitance measurement

An application specific integrated circuit or ASIC (MSC) is connected to a plurality of bridge type sense elements ( ) for analog multiplexing ( ) the outputs from a selected sense element to a common signal conditioning path ( ). The bridge type sense elements are biased through an electronically programmable resistor ( ) to derive a temperature signal. The signal conditioning path provides electronically programmable correction for offset and gain proportional to the sensed condition, e.g., fluid pressure. Complete sensor characterization data provided at the time of manufacture is stored in non-volatile memory ( ) which is downloaded to a host controller ( ) on command. The ASIC also includes diagnostic test bridges (BR BR ) for diagnosing ASIC faults and a signal diagnostic path ( ) for diagnosing sense element and sense element connection faults. Characterization data downloaded to the host controller enables the controller to mathematically correct remaining temperature, condition (e.g., pressure) and diagnostic signal errors,

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Providence, RI, United States of America

John A Powning