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Photometric apparatus and method

  • US 4,350,441 A
  • Filed: 06/30/1980
  • Issued: 09/21/1982
  • Est. Priority Date: 06/30/1980
  • Status: Expired due to Term
First Claim
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1. A photometric apparatus for determining the absorbance ratio in a sample of two different wavelength lights, said apparatus comprising:

  • means for providing a light of a first wavelength having, when said light is energized, a postsample intensity after said light is directed through the sample;

    means for providing a light of a second wavelength having, when said light is energized, a postsample intensity after said light is directed through the sample;

    means for alternately energizing said first and second lights;

    means for detecting said postsample intensities of said first and second lights;

    a comparator having two inputs and an output;

    a digital to analog converter having two inputs and an output;

    means coupling the output of said digital to analog converter to an input of said comparator;

    means coupled to the other input of said comparator for providing a signal that is proportional to said detected postsample intensity of said first light;

    means coupled to an input of said digital to analog converter for providing a signal that is proportional to said detected postsample intensity of said second light;

    an up/down counter having an up/down input and an output;

    means coupling the output of the comparator to the up/down input of said counter;

    means coupling the output of the up/down counter to the other input of said digital to analog converter; and

    means for clocking said up/down counter.

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