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Non-intrusive impedance-based cable tester

  • US 5,977,773 A
  • Filed: 08/15/1997
  • Issued: 11/02/1999
  • Est. Priority Date: 08/15/1997
  • Status: Expired due to Term
First Claim
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1. An apparatus for determining the location of a discontinuity in an electrical cable comprising:

  • a) a variable frequency oscillator for applying a variable frequency oscillating test signal to a signal injection point at one end of an electrical cable under test;

    b) a reference resistor disposed between said oscillator and said signal injection point; and

    c) a microcontroller for controlling operation of said oscillator, said microcontroller including means for determining a frequency of said test signal at which an electrical impedance at said signal injection point between said oscillator and said cable is a minimum, and determining from said frequency, the distance from said injection point to a discontinuity in said cable, said microcontroller further including means for comparing a voltage magnitude at said signal injection point to a voltage magnitude at an oscillator side of said reference resistor, and determining that said discontinuity is;

         1) an open circuit if said voltages are approximately equal to one another, and

         2) a short circuit if said signal injection point voltage is approximately zero volts.

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