OHMMETER FOR MEASURING THE INTERNAL RESISTANCE OF A BATTERY AND DIRECTLY READING THE MEASURED RESISTANCE VALUE

  • US 3,753,094 A
  • Filed: 07/24/1972
  • Issued: 08/14/1973
  • Est. Priority Date: 07/01/1969
  • Status: Expired due to Term
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First Claim
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1. An ohmmeter for measuring the internal resistance of a battery comprising a DC power source circuit;

  • a DC constant voltage circuit for producing a DC constant voltage output from the DC power of said DC power source circuit, a DC-AC conversion circuit for converting said DC constant voltage output to an AC constant current having a relatively high frequency;

    said DC constant voltage circuit being a series-type constant voltage circuit comprising a control transistor having a collector connected to one output terminal of said DC power source circuit, an emitter connected to one input terminal of said DC-AC conversion circuit, and a base connected to said one output terminal of said DC power source circuit through a resistor; and

    a reference transistor having an emitter connected to the base of said control transistor and a base connected to the other output terminal of said DC power source circuit through a constant voltage diode and also to said one output terminal of said DC power source circuit through another resistor;

    a DC blocking device, said AC constant current being applied to a battery to be measured through said DC blocking device, said DC blocking device preventing DC current from flowing from the battery; and

    an AC voltmeter circuit including an indicatOr connected across the battery for measuring the AC voltage drop of the battery due to its internal resistance, said indicator of said AC voltmeter circuit being adapted to indicate directly the internal resistance of the battery.

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