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US6339960: Non-intrusive pressure and level sensor for sealed containers

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Filing Information

Inventor(s) R. Daniel Costley · Mark Henderson ·
Assignee(s) Mississippi State University ·
Primary Examiner Hezron Williams ·
Assistant Examiner Jacques Saint-Surin ·
Application Number US9698227
Filing date 10/30/2000
Issue date 01/22/2002
Predicted expiration date 10/30/2020
U.S. Classifications 735/79  · 737/2  · 73/52  ·
International Classifications --
Kind CodeB1
International Classifications 73579 · 73574 · 73570 · 73599 · 73602 · 73 1201 · 73 52 · 73290 V · 73702 · 73 5406 ·
6 Claims, 26 Drawings


Abstract

A method and apparatus for determining the internal pressure of a sealed container are disclosed. The method involves: exciting a lid of the container so as to create at least two modes of vibration having separate frequencies, wherein said frequencies are fundamental, f1, and a second frequency, preferably the second axisymmetric mode, f2; detecting the vibration resulting from said exciting to determine f1, and f2; using f2, which is indicative of internal pressure, to calculate a first value for internal pressure using a first mathematical model that is calibrated to the lid on the sealed container; using f1, which is indicative of volume of contents, to calculate the volume of contents in the sealed container using a second mathematical model that is calibrated to the lid on the sealed container, wherein a natural frequency of said lid is a function of said internal pressure and said volume of contents; and compensating for said volume of contents to determine a second value for internal pressure, wherein said second value for internal pressure is more reliable than said first value for internal pressure. The apparatus for determining the internal pressure of a sealed container of the invention includes: means for exciting a lid of the container so as to create at least two modes of vibration having separate frequencies, wherein said frequencies are fundamental, f1, and a second frequency, preferably the second axisymmetric mode, f2; detecting means for detecting vibration resulting from the exciting of said container to determine f1, and f2; calculating means for calculating a first value for internal pressure of said container using f2; calculating means for calculating the volume of contents of said container using f1; wherein a natural frequency of said lid is a function of said internal pressure and said volume of contents; and calculating means for compensating for said volume of contents to determine a second value for internal pressure, wherein said second value for internal pressure is more reliable than said first value for internal pressure.

Independent Claims | See all claims (6)

  1. 1. A method for determining an internal pressure of a sealed container, comprising: exciting a lid of the sealed container so as to create at least two modes of vibration having separate frequencies, wherein said frequencies are fundamental, f1, and a second frequency, f2; detecting the vibration resulting from said exciting to determine f1, and f2; using f2, which is indicative of internal pressure, to calculate a first value for internal pressure using a first mathematical model that is calibrated to the lid on the sealed container; using f1, which is indicative of volume of contents, to calculate the volume of contents in the sealed container using a second mathematical model that is calibrated to the lid on the sealed container; wherein a natural frequency of said lid is a function of internal pressure and volume of contents; and compensating for said volume of contents to determine a second value for internal pressure, wherein said second value for internal pressure is more reliable than said first value for internal pressure.
  2. 3. An apparatus for determining an internal pressure of a sealed container, comprising: means for exciting a lid of the sealed container so as to create at least two modes of vibration having separate frequencies, wherein said frequencies are fundamental, fd1; and a second frequency, f2; detecting means for detecting vibration resulting from the exciting of said container to determine f1 and f2; calculating means for calculating a first value for internal pressure of said container using f2; calculating means for calculating the volume of contents of said container using f1; wherein a natural frequency of said lid is a function of said internal pressure and said volume of contents; and calculating means for compensating for said volume of contents to determine a second value for internal pressure, wherein said second value for internal pressure is more reliable than said first value for internal pressure.
  3. 5. A method of determining the internal pressure and level of contents within a container comprising the steps of: (a) storing container data into a memory; (b) exciting a lid of the container so as to create at least two modes of vibration having separate frequencies, wherein said frequencies are fundamental, f1, and a second frequency, f2; (c) detecting the vibration resulting from said exciting to determine f1 and f2; (d) producing a frequency spectrum of the detected vibration; (e) isolating values of f1 and f2 from the frequency spectrum; (f) using f2 to calculate an internal pressure using a first mathematical model that is calibrated to the sealed container; and (g) using f1 to calculate the volume of contents in the sealed container using a second mathematical model that is calibrated to the sealed container.

References Cited

U.S. Patent Documents

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* cited by examiner

Other Publications

Thinnes, G.L., et al., “Resonance Analysis To Determine Pressurization of 55 Gallon Waste Containers”, Idaho National Engineering Laboratory (U.S. Department of Energy), INEL-95/0635, published Dec. 1995.
Morse, P.M., “Vibration and Sound”, Massachusetts Institute of Technology (American Institute of Physics), Chapter 5, § 19 and §21, published 1983.
Sinha, D.N., et al., “Noninvasive Drum Pressure Measurements Using Acoustic Resonance Spetroscopy”, Los Alamos National Laboratory (Results of Sep. 19-20 1995 Study), published Oct. 24, 1995.
Costley, R. D., et al., “Acoustic Detection of Pressure in Sealed Drums”, J. Acoustical Society of America, (2pEA4), vol. 106, No. 4, Pt. 2, pp. 2166-2167, Oct. 1999.
Reismann, H., “Elastic Plates Theory and Application”, John Wiley & Sons, NY, Chapters 6 and 7, published 1988.
H. Patel et al., “Drum Pressure Monitor”, Review of Progress in Quantitative Nondestructive Evaluation, vol. 18, pp. 2087-2093, 1999.
P. K. Raju, “Engineering Acoustics, Physical Acoustics and Structural Acoustics and Vibration: Acoustic Nondestructive Evaluation: New Directions and Techniques, Part II”, J. Acoust. Soc. Am., vol. 106, No. 4, Pt. 2, pp, 2166-2167, Oct. 1999.
H. Patel, “The Mode Shapes and Natural Frequencies of Various Types of Storage Drums Under Different Pressures”, Mississippi State University, pp. 1-54, Aug. 1998.

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