Patent ID: 6695964
Filing Date: 2004-02-24
Classification: G01N

Abstract:
A NOx gas concentration sensor for measuring the NOx concentration in an exhaust gas comprising NOx, O2, CO2 and H2O, comprising:(a) a ceramic body comprising an electrolyte having an electrically controllable conducting rate of oxygen ion; (b) a first pair and a second pair of electrodes formed on said ceramic body; (c) a flow channel in said ceramic body for passage of the exhaust gas; (d) means for extracting said O2 from the exhaust gas via said ceramic body to outside the flow channel so as to form a residual gas in said flow channel; (e) means for applying a first voltage and a second voltage across the first pair and the second pair of electrodes, respectively, said first voltage maximizing a gain by the dissociation of the NOx gas contained in said residual gas without substantial dissociation of the H2O gas contained in said residual gas and said second voltage maximizing a gain by the dissociation of the NOx gas contained in said residual gas with substantial dissociation of the H2O gas contained in said residual gas; (f) means for measuring a first current flowing between said first pair of electrodes across which said first voltage is applied; (g) means for measuring a second current flowing between said second pair of electrodes across which said second voltage is applied; and (h) means for determining the NOx concentration in the exhaust, said determination of the NOx gas concentration being based on the first current being corrected by the second current.