Patent ID: 6289719
Filing Date: 2001-09-18
Classification: G01N

Abstract:
A method for operating a gas sensor having two sensor electrodes and supplying an output signal (U.sub.sen) thereacross, the gas sensor including: an ion conducting ceramic and said sensor electrodes being disposed therein; and, an electric heater for heating said ceramic and said sensor electrodes to ensure proper operation of said gas sensor, said electric heater being electrically insulated from said sensor electrodes with leakage resistances being present between said heater and said sensor electrodes in an order of magnitude of several megaohms at high temperatures whereby an unwanted electrical leakage current flows from said heater to said sensor electrodes when said electric heater is energized, the method comprising the steps of:connecting an evaluation circuit downstream of said sensor electrodes for evaluating said output signal (U.sub.sen) with said unwanted leakage current being superposed thereon causing errors;applying a pulsewidth modulated heater voltage signal (U.sub.PWM) to said heater;superposing a compensation signal (U.sub.comp) on said output signal (U.sub.sen) of said sensor electrodes; and,forming said compensation signal (U.sub.comp) so as to be counterclocked and inverted to said pulsewidth modulated heater voltage signal (U.sub.PWM) to compensate said unwanted leakage current thereby correcting said errors.