Signal conditioning methods and circuits for a capacitive...

Details Signal conditioning methods and circuits for a capacitive... Signal conditioning methods and circuits for a capacitive...

2007-07-09

2008-11-25

Lefkowitz, Edward (Department: 2855)

Measuring and testing

Tire, tread or roadway

Tire inflation testing installation

C073S146000, C341S144000, C341S155000, C341S172000

Reexamination Certificate

active

07454967

ABSTRACT:
A tire pressure monitoring system is provided that includes a switched capacitor circuit having a clock with two non-overlapping clock phases that control a state of analog switches of the switched capacitor circuit. The system uses tire pressure sensor MEMS capacitors that are measured differentially. A capacitance-to-voltage converter is connected to the MEMS sense capacitor, and a sigma-delta converter having a comparator with a first digital output state and a second digital output state is used. The first output state is a sum of reference voltages and the second output state is a difference of the reference voltages. An average value of the capacitance-to-voltage converter output is driven to a zero value and a digital output is provided of the average output states that is equal to a difference between the MEMS capacitors divided by their sum multiplied by a ratio of the reference voltages.

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