US Patent 7845224 Liquid level sensor and liquid level estimation method

A sensor for detecting a liquid level, including a measurement capacitor, a reference capacitor, an integrating capacitor, a calibration capacitor, a controller, an amplifier, a comparator, and a complementary calibration capacitor. The controller implements operations, over accumulation periods and for given target and discharge capacitors, of a target capacitor charging, a charge transfer, a decision, a conditional discharge, and a return. The target and discharge capacitors given at each period are taken from pairs of capacitors, including the measurement and calibration capacitors and the reference and complementary calibration capacitors. A method estimates the liquid level using the sensor in a vehicle.