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Method and apparatus for determining a change of the flow state of flowable substances from its static state to its flowing state or vice verse

  • US 4,112,740 A
  • Filed: 07/18/1977
  • Issued: 09/12/1978
  • Est. Priority Date: 01/13/1977
  • Status: Expired due to Term
First Claim
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1. A method of determining a change of the flow state of a flowable substance, comprising the steps of:

  • transmitting ultrasonic waves of substantially constant frequency to a spatial region of the substance;

    receiving ultrasonic waves backscattered by the substance;

    transforming the backscattered ultrasonic waves into a primary signal which is amplitude and phase modulated in accordance with the backscattering;

    demodulating the primary signal to obtain a modulation signal which can be subdivided into a spectrum of signal components of different frequencies and possessing pseudo periods which are defined as the time spacing between successive mutually corresponding momentary values of the signal modulation;

    determining at least one time point at a mean value of the psuedo periods having a monotonous variation with time which entails a monotonous variation with time of the time duration of a predetermined number of pseudo periods;

    comparing a time duration corresponding to a predetermined number of pseudo periods with a predetermined time duration; and

    whereinthe time duration of the predetermined number of pseudo periods traverses the predetermined time duration in the course of its monotonous variation with time.

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