Patent ID: 7301330

Claim:
An electronic sensing circuit comprising a sensor with an output for a sensing signal; a comparator with a first and second comparator input, the output of the sensor being coupled to the first comparator input; a control circuit arranged to switch the sensing circuit from an upward tracking mode to a downward relative level detection mode, to a downward tracking mode, to an upward relative level detection mode and back to the upward tracking mode successively; a digital to analog converter, coupled to receive digital control signals from the control circuit, the control circuit having first output coupled to the digital to analog converter to cause the digital to analog converter to supply first and second output signals determined by first and second digital control signal values to the second comparator input in the upward and downward tracking mode respectively, and to supply a third output signal corresponding to an average of the first and second output signals to the second comparator input in the relative level detection modes; the control circuit having an input coupled to the output of the comparator, the control circuit controlling one directional upward tracking by the first digital control signal value of upward changes of the sensing signal in the upward tracking mode, and controlling one directional downward tracking by the second digital control signal value of downward changes of the sensing signal in the upward tracking mode.