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Method of testing the integrity of an ultrasonic system for sensing liquid-fluid interfaces

  • US 4,299,114 A
  • Filed: 06/10/1980
  • Issued: 11/10/1981
  • Est. Priority Date: 06/10/1980
  • Status: Expired due to Term
First Claim
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1. A method for testing the integrity of an ultrasonic system for sensing a liquid-fluid interface in a container, said system comprising:

  • (a) first and second crystals, each of said crystals having a relatively high resonant frequency and a relatively low resonant frequency;

    (b) a support structure with first and second end arms connected by a cross member, said first crystal being bonded to said first end arm and said second crystal being bonded to said second end arm, said first and second crystals being positioned opposite each other across a gap between said first and second end arms in said container;

    (c) means for selectively enabling said first crystal to resonate either at its relatively high resonant frequency or at its relatively low resonant frequency, said relatively high resonant frequency being sufficiently high to cause an ultrasonic signal to be transmitted into said gap without causing appreciable ultrasonic transmission through said cross portion of said support structure, said relatively low resonant frequency being sufficiently low to cause transmission of a detectable ultrasonic signal through said cross member; and

    (d) means for detecting resonance induced in said second crystal due to resonance of said first crystal at either its relatively high resonance frequency or its relatively low resonance frequency;

    said testing method comprising the steps of causing said first crystal to resonate at its relatively low resonant frequency irrespective of whether the liquid-fluid interface lies within said gap in order to cause ultrasonic transmission through said cross member, and detecting resonance in said second crystal at said relatively low resonant frequency, thereby indicating that the ultrasonic system is operational.

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