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Fluid flow measuring apparatus

  • US 4,320,666 A
  • Filed: 07/20/1979
  • Issued: 03/23/1982
  • Est. Priority Date: 07/22/1978
  • Status: Expired due to Term
First Claim
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1. Fluid flow measuring apparatus comprising:

  • means to generate an electrical carrier signal;

    means to generate a modulation signal;

    means to frequency modulate the carrier signal in accordance with the modulation signal;

    first and second transducers which are spaced-apart along the fluid flow;

    means to feed the modulated carrier signal to one of said transducers so that said transducer transmits ultrasonic energy through the fluid to be received by the other transducer;

    a phase-locked loop to maintain a fixed relationship between the phase of the modulation fed to the transmitting transducer and the phase of the modulation received by the receiving transducer by adjustment of the frequency of said modulation signal; and

    means responsive to said frequency of said modulation signal to indicate speed of fluid flow.

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