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Electronic thermometer

  • US 4,023,094 A
  • Filed: 02/26/1975
  • Issued: 05/10/1977
  • Est. Priority Date: 06/23/1972
  • Status: Expired due to Term
First Claim
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1. In combination for determining an unknown value of impedance, comprising:

  • first impedance means for providing the unknown value of impedance to be determined;

    second impedance means for providing an impedance adjustable through a range of known values of impedance;

    third impedance means providing a first particular value of impedance;

    fourth impedance means providing a second particular value of impedance;

    first connecting means coupling the first, second, third and fourth means in a bridge to form first and second impedance branches each including an individual pair of the first, second, third and fourth impedance means and each including a common terminal between the impedance means in that branch;

    fifth means responsive to the voltage on the common terminal in the first impedance branch and the voltage on the common terminal in the second impedance branch for producing an output voltage representing any voltage difference between the voltages on such common terminals;

    sixth means responsive to the output voltage from the fifth means for introducing such output voltage to the first and second impedance branches in a positive feedback to energize such impedance branches for the production, on the common terminal in the first impedance branch and the common terminal of the second impedance branch, of voltages having a first value for unbalances of a first particular amplitude in the relative values of the impedances in the first and second impedance branches and voltages having a second particular amplitude distinctively different from the first particular amplitude for unbalances of a second polarity in the relative values of the impedance in the first and second impedance branches;

    the second means comprising;

    fifth impedance means for providing a particular value of impedance;

    sixth impedance means for providing a particular value of impedance;

    seventh impedance means for providing a particular value of impedance;

    eighth impedance means for providing an impedance adjustable through a range of known values of impedance;

    second connecting means coupling the fifth, sixth, seventh and eighth impedance means to form third and fourth impedance branches each including an individual pair of the fifth, sixth, seventh and eighth impedance means and a common terminal between the impedance means in that branch;

    ninth means responsive to the voltage on the common terminal in the third impedance branch and the voltage on the common terminal in the fourth impedance branch for producing an output voltage representing any voltage difference between the voltages on such common terminals; and

    tenth means responsive to the output voltage from the tenth means for introducing such output voltage to the third and fourth impedance branches to energize such impedance branches for controlling the production of the voltages on the common terminals in the third impedance branch and the common terminal in the fourth impedance branch in accordance with such output voltage.

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