Method for operating a sensor for determining the concentration of oxidizing gases in gas mixtures

Abstract

Method for operating a sensor for determining the concentration of oxidizing gases in gas mixtures, especially of the nitrogen oxide concentration in exhaust gases of internal combustion engines, wherein the sensor includes: at least one chamber ( ) mounted in a solid state electrolyte ( ), the chamber being connected to the gas mixture via a first diffusion barrier ( ); a second chamber ( ) arranged in the solid state electrolyte ( ) and the chamber having a pregivable constant oxygen partial pressure; on the solid state electrolyte, an oxygen pump electrode ( ) subjected to the exhaust gas; a further oxygen pump electrode ( ) as well as an NO pump electrode ( ) in the at least one chamber ( ); and an oxygen reference electrode ( ) arranged in the second chamber ( ); and at least a voltage is made available at the electrodes and at least a pump current is evaluated as a measurement signal. The method is characterized in that the voltages (U_IPE; U_O U_NO), which are applied to the electrodes, are changed in dependence upon the currents, which flow in the electrode feed lines and/or between the electrodes ( ), during operation of the sensor in such a manner that the voltages correspond to pregivable desired values, these voltages being applied to the electrodes ( ) in the interior of the sensor.