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Nondispersive optical monitor for nitrogen-oxygen compounds

  • US 5,818,598 A
  • Filed: 12/20/1996
  • Issued: 10/06/1998
  • Est. Priority Date: 12/20/1996
  • Status: Expired due to Fees
First Claim
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1. A method of determining a concentration of nitrogen dioxide in a sample, nitrogen dioxide having a transmission spectrum defined by at least one absorption line and an average broadband transmission varying according to a wavelength dependence, the method comprising the steps of:

  • a. providing in a first optical path a correlation filter, comprising a first cell for containing nitrogen dioxide at a correlation filter pressure;

    b. providing in a second optical path a compensating filter, having an average broadband transmission that varies according to the wavelength dependence without the at least one absorption line;

    c. supplying light from a first light source to the correlation filter;

    d. supplying light from a second light source to the compensating filter;

    e. merging light that has passed through the correlation filter and light that has passed through the compensating filter in a combined optical path;

    f. measuring light in the combined optical path;

    g. supplying light from the combined path to the sample; and

    h. measuring light leaving the sample.

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