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Thermocouple system having a PN junction for cold junction compensation

  • US 3,921,453 A
  • Filed: 03/08/1974
  • Issued: 11/25/1975
  • Est. Priority Date: 03/08/1974
  • Status: Expired due to Term
First Claim
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1. A solid state thermocouple actuated electronic switch circuit with solid state cold junction compensation, said circuit comprising:

  • a thermocouple having a junction of two dissimilar metals with each metal being a current conducting member;

    a first amplifier having its input terminals electrically connected respectively to said current conducting members of said thermocouple forming a cold junction and responsive to the voltage signal generated by said thermocouple for generating a first amplifier signal;

    a solid state, semiconductor cold junction compensator means generating a voltage responding to the temperature of said cold junction;

    a second amplifier having its input electrically connected to said solid state cold junction compensator means and responsive to said voltage signal generated thereby for generating a second amplified signal;

    a reference temperature signal generator means generating a third signal representing the actuating temperature of the switch circuit;

    a summing-comparator responsive to the summation of said first, second and third signals for generating a fourth signal whenever the magnitude summation of said first and second signal exceeds the magnitude of said third signal; and

    a solid state switching means responsive to said fourth signal for changing its state of conduction.

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