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Simultaneously resonated, multi-mode crystal force transducer

  • US 4,144,747 A
  • Filed: 01/30/1978
  • Issued: 03/20/1979
  • Est. Priority Date: 01/30/1978
  • Status: Expired due to Term
First Claim
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1. A force transducer comprising:

  • a piezoelectric crystal having two opposite surfaces and a predetermined thickness, said surfaces lying generally along orthogonal axes determined from the structure and cut of the crystal, where a force applied to the crystal in the direction of one of said axis produces a shift in the crystals resonant frequency;

    said crystal having at least two different electrode sets disposed on the surfaces of said crystal;

    means for holding said crystal in a predetermined position, and for applying a received external force to said crystal at a predetermined angle with reference to said one axis;

    first oscillator means connected to one of said two sets of electrodes for resonating said crystal at a first resonant frequency, said first resonant frequency being variable as a first function of the applied force;

    second oscillator means connected to said other set of electrodes for resonating said crystal at a second resonant frequency indicative of an anharmonic resonant frequency having more than one resonant antinode lying in a direction angularly disposed to said one axis, said anharmonic resonant frequency being variable as a second function of the received force different from said first function;

    means responsive to said first and second resonant frequencies for generating a signal indicative of the received force.

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