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Digital silver ion concentration controller for the precipitation of silver halide emulsions

  • US 4,933,870 A
  • Filed: 07/14/1988
  • Issued: 06/12/1990
  • Est. Priority Date: 07/14/1988
  • Status: Expired due to Term
First Claim
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1. Apparatus for controlling the concentration of silver ions during the precipitation of a silver halide in a precipitation vessel comprising:

  • a first means for controllably introducing a silver salt into said precipitation vessel;

    a second means for controllably introducing a halide salt into said precipitation vessel;

    an ion sensor positioned in said precipitation vessel for generating a voltage representative of the amount of silver ion in solution therein;

    a temperature sensor positioned in said precipitation vessel for generating a voltage representative of the temperature of the silver ion solution therein;

    means for converting the ion sensor voltage and the temperature sensor voltage to digital values;

    computer means for receiving the digital values of the ion sensor and the temperature sensor for converting the digital value of the ion sensor to a digitized concentration value by computing the equation;

    wherein;

    R is a gas constantT is the absolute temperature of the solution in degrees KelvinF is the Faraday constant and by transforming the digitized concentration value to an equivalent constant coefficient differential equation;

    
    
    space="preserve" listing-type="equation">dY/dt+aY=bD+bU where;

    Y=[Ag+]1/n and where;

    n=2D is the disturbance of the systemU is the control effortb is a constant, anda is a constant;

    means for comparing the transformed digitized concentrated value against a digitized set point value to provide a difference signal; and

    means for controlling said first and said second means as a function of said difference signal so as to drive said difference signal towards a zero value.

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