Method of measuring a physical parameter and electronic interface circuit for a capacitive sensor for implementing the same

Abstract

The method is for measuring a physical parameter via an electronic circuit connected to a two differential capacitor sensor having two fixed electrodes and a common moving electrode. The circuit supplies first and second digital measuring signals. Each measuring cycle consists on biasing fixed electrodes by a first biasing and a second biasing reverse of the first biasing, alternated with biasing the electrodes by the measuring voltage based on first and second digital signals. Each conversion starts by a small step value added to or subtracted from each digital signal in each cycle. If the successive identical amplifier output states counted or counted down by a counter is higher than a threshold, a large step value is added to or subtracted from the digital signals in each cycle. Re-adaptation to the small step value occurs when a sign change is detected in the counter, until the conversion end.