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Frequency encoding closed loop circuit with transducer

  • US 4,408,169 A
  • Filed: 05/18/1981
  • Issued: 10/04/1983
  • Est. Priority Date: 05/18/1981
  • Status: Expired due to Fees
First Claim
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1. A method for producing an output frequency which is a function of the amplitude of a varying physical quantity acting on a transducer having an output impedance, the method comprising the steps of:

  • generating, in a relaxation oscillator with an input impedance, a digital drive signal at the output frequency;

    driving the transducer with a function of the digital drive signal and producing an amplitude modulated bilevel signal in-phase with the drive signal and having an amplitude which is a function of the amplitude of the physical quantity sensed by the transducer;

    isolating the output impedance of the driven transducer from the input impedance of the relaxation oscillator;

    combining the drive signal and the amplitude modulated bilevel signal, thereby providing a composite signal; and

    feeding the composite signal back as the input to the relaxation oscillator.

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