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Method and apparatus for measuring NOx gas concentration

  • US 6,695,964 B1
  • Filed: 06/07/2000
  • Issued: 02/24/2004
  • Est. Priority Date: 12/02/1996
  • Status: Expired due to Term
First Claim
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1. 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.

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