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OBD calorimetric sensor system with offset error correction

  • US 6,003,307 A
  • Filed: 02/06/1998
  • Issued: 12/21/1999
  • Est. Priority Date: 02/06/1998
  • Status: Expired due to Term
First Claim
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1. An on-board diagnostic method for determining if the emissions of an internal combustion engine in a vehicle with a catalytic converter comply with regulatory standards comprising the steps of:

  • a) providing a calorimetric sensor downstream of said catalytic converter developing electrical sensor signals indicative of the concentration of at least one, specific regulated gaseous emission in the vehicle'"'"'s exhaust gases;

    b) cyclically operating said engine between a first operating condition producing exhaust gases having a first composition of gaseous emissions and a second operating condition producing exhaust gases having a second, composition of gaseous emissions with different concentrations of specific emissions than said first mixture;

    c) determining a delta signal indicative of the difference between said calorimetric signals generated for said first and second gas mixtures in any given cycle; and

    ,d) comparing said delta signal to a stored value correlated to the efficiency of said catalytic converter to convert said specific gaseous emissions to harmless gaseous emissions to satisfy said regulatory standards whereby a relative sensor signal, independent of an absolute value, senses concentrations of specific regulated gaseous emissions to determine compliance with said regulatory standards.

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