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Method and ohmmeter for measuring very low electric resistances

  • US 4,698,584 A
  • Filed: 10/22/1985
  • Issued: 10/06/1987
  • Est. Priority Date: 06/25/1985
  • Status: Expired due to Term
First Claim
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1. An ohmmeter for measuring a very low electric resistance, comprising:

  • a source of electric energy for delivering a one-polarity measuring current flowing through an electrically conducting object presenting said very low resistance so as to create a voltage drop proportional both to the magnitude of the measuring current and to said very low electric resistance;

    means for detecting said measuring current and for producing a signal representative of the magnitude of said measuring current;

    first integration means for integrating with respect to time and from a given instant the signal representative of the magnitude of the measuring current in order to produce a first integration signal representative of the quantity of measuring current which has flowed through the electrically conducting object from said instant;

    means for generating an interruption signal when said first integration signal reaches a predetermined amplitude, that is, when a predetermined quantity of measuring current has flowed through the electrically conducting object from said instant;

    second integration means for integrating with respect to time said voltage drop proportional to the magnitude of the measuring current and to said very low electric resistance in order to produce a second integration signal;

    means for controlling said first and second integration means so as to simultaneously start the integration of the signal representative of the magnitude of the measuring current carried out by the first integration means and the integration of said voltage drop carried out by the second integration means; and

    means for stopping the integration of said voltage drop carried out by the second integration means in response to said interruption signal;

    the second integration signal having upon stopping of the integration of said voltage drop carried out by the second integration means an amplitude which is related to said predetermined quantity of measuring current and which constitutes a measure of said very low electric resistance.

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