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Modulation schemes for on-board diagnostic exhaust system

  • US 5,709,082 A
  • Filed: 05/28/1996
  • Issued: 01/20/1998
  • Est. Priority Date: 06/27/1994
  • Status: Expired due to Fees
First Claim
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1. An on-board diagnostic system comprising:

  • a combustion engine, and a combustion emission collection system operatively connected to said engine, and an exhaust measuring system constructed and arranged to be useable as the combustion engine is in operation on a regular continuous basis, said exhaust measuring system comprising an exhaust sampling port, a sample cell, and an infrared system;

    said exhaust sampling port communicating with the exhaust collection system;

    said sample cell communicating with the exhaust sampling port, and an air pump communicating with the sample cell; and

    said infrared system, having a filter selective for detecting light associated with the presence of hydrocarbon, connected to the sample cell, and wherein said pump is controlled to periodically purge the sample cell of exhaust gas and fill the sample cell with air and wherein the infrared system is controlled to take a first measurement when the sample cell is filled with air and a second measurement, independent of the first measurement, when the sample cell is filled with exhaust gas, and further comprising a comparator for determining the ratio between the first and second measurements, and wherein said infrared system includes only one infrared detector.

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