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Resistance bridge and its use in conversion systems

  • US 5,909,132 A
  • Filed: 08/13/1997
  • Issued: 06/01/1999
  • Est. Priority Date: 02/05/1996
  • Status: Expired due to Fees
First Claim
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1. A Δ

  • R-to-digital conversion system comprising;

    four first impedance elements of substantially equal values, two of said first impedance elements connected at a first junction to form a first impedance pair and two others of said first impedance elements connected at a second junction to form a second impedance pair, each of said pairs having first and second ends, the impedance of at least one of said first impedance elements changing in response to an external force to which said first impedance elements are exposed, said first and second impedance pairs connected at said first ends;

    a first reference voltage coupled to said first junction of said first impedance elements of said first impedance pair; and

    a grounding voltage coupled to said second junction of the second impedance pair;

    a second impedance element having first and second nodes and having a value less than one percent the value of said first impedance elements, said first node of said second impedance element coupled to said second end of said first impedance pair and said second node of said second impedance element coupled to the second end of said second impedance pair, and means for providing a first differential voltage signal between said first node of said second impedance element and said first ends of said first and second impedance pairs, and means for providing a second differential voltage signal between said second node of said second impedance element and said first ends of said first and second impedance pair, magnitudes and signs of said differential voltage signals depending on the impedances of said first and second impedance elements and being responsive to changes in the impedance of at least one of said four first impedance elements;

    switching means for alternatively selecting between said first and second differential voltage signals, said selected differential voltage signals being steady dc values;

    integrating means for receiving the selected differential voltage signals to produce an output waveform representing an integral of said first and second differential voltage signals, said output waveform being a triangular waveform; and

    a pulse-forming circuit coupled to said integrating means for generating an output signal of a series of digital pulses from said output waveform;

    wherein said switching means is switched by said output signal.

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