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US5822274: Method and apparatus for acoustically measuring the level of liquid in a tank

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Filing Information

Inventor(s) Carl R. Haynie · Jeffrey D. Wilson ·
Assignee(s) Flowline Inc. ·
Attorney/Agent(s) Sheppard, Mullin, Richter & Hampton ·
Primary Examiner Daniel T. Pihulic ·
Application Number US8631344
Filing date 04/12/1996
Issue date 10/13/1998
Predicted expiration date 04/12/2016
U.S. Classifications 367/99  · 367/908  ·
International Classifications G01S 1508  ·
Kind CodeA
International Classifications 367908;902;99;105 ·
33 Claims, No Drawings


Abstract

A time-domain reflectometer is disclosed for reliably measuring the level of a liquid in a tank. The reflectometer emits an acoustic signal into a waveguide that projects downwardly into the tank and receives a return acoustic signal reflected from the surface of the liquid. The time delay between the transmitted acoustic signal and the reflected acoustic signal is a measure of the level of the liquid, and the reflectometer converts this level measurement into a electrical current that is linearly proportioned between predetermined minimum and maximum values. In addition, the reflectometer incorporates a liquid- and vapor-impervious membrane disposed in the path of the transmitted and reflected acoustic signals, adjacent to the transmitter and receiver, to prevent the escape of liquid and vapor from the tank and to isolate the electronics, including the transmitter and receiver, from such liquid and vapor.

Independent Claims | See all claims (33)

  1. 1. A method for measuring the level of a liquid in a tank, comprising:positioning an acoustic transducer in a predetermined position relative to the tank and conditioning the transducer to transmit an acoustic signal toward a surface of a liquid located in the tank, which reflects the acoustic signal back to the transducer;detecting the reflected acoustic signal and producing a corresponding detection signal;measuring the time delay from the time the acoustic signal is transmitted by the acoustic transducer until the time of the detection signal, to produce a time delay measurement;generating a range enable signal that begins a first predetermined time delay after the transducer transmits the acoustic signal and that ends a second predetermined time delay after the transducer transmits the acoustic signal, wherein the first predetermined time delay corresponds to the time required for the acoustic signal to travel from the transducer to the liquid surface and back to the transducer when the liquid level is at a predetermined first level, and wherein the second predetermined time delay corresponds to the time required for the acoustic signal to travel from the transducer to the liquid surface and back to the transducer when the liquid level is at a predetermined second level; andcomparing the detection signal with the range enable signal, to produce a liquid level signal having a first value when the liquid level is determined to be at the predetermined first level, a second value when the liquid level is determined to be at the predetermined second level, and a linearly proportionate value between the first and second values when the liquid level is determined to be between the predetermined first and second levels.
  2. 9. A time-domain reflectometer for measuring the level of a liquid in a tank, comprising:an acoustic transmitter positioned in a predetermined position relative to the tank and configured to transmit an acoustic signal toward a surface of a liquid located in the tank, which reflects the acoustic signal back to the transducer;an acoustic receiver positioned in a predetermined position relative to the tank and configured to receive the reflected acoustic signal and to produce a corresponding detection signal;a timing circuit that measures the time delay from the time the acoustic signal is transmitted by the acoustic transducer until the time the acoustic receiver produces the detection signal, to produce a time delay measurement;a range enable circuit that produces a range enable signal that begins a first predetermined time delay after the transmitter transmits the acoustic signal and that ends a second predetermined time delay after the transmitter transmits the acoustic signal, wherein the first predetermined time delay corresponds to the time required for the acoustic signal to travel from the transmitter to the liquid surface and back to the transmitter when the liquid level is at a predetermined first level, and wherein the second predetermined time delay corresponds to the time required for the acoustic signal to travel from the transmitter to the liquid surface and back to the transmitter when the liquid level is at a predetermined second level; andan output circuit that compares the detection signal with the range enable signal, to produce a liquid level signal having a first value when the liquid level is determined to be at the predetermined first level, a second value when the liquid level is determined to be at the predetermined second level, and a linearly proportionate value between the first and second values when the liquid level is determined to be between the predetermined first and second levels.
  3. 17. A time-domain reflectometer that measures the level of a liquid in a tank, comprising:an acoustic transmitter configured to transmit an acoustic signal into the tank, whereupon the acoustic signal is reflected from the surface of any liquid disposed in the tank;an acoustic receiver configured to receive the reflected acoustic signal and produce an electrical receive signal;an electrical circuit that processes the electrical receive signal, to produce a measurement of the level of the liquid in the tank;a support that secures the acoustic transmitter and the acoustic receiver in predetermined locations relative to the tank, wherein the support comprisesa sensor housing having side-by-side openings for supporting the acoustic transmitter and the acoustic receiver, anda base having a lower opening that communicates with the interior of the tank and further having side-by-side upper openings that communicate with the lower opening and that align with the side-by-side openings of the sensor housing; anda liquid- and vapor-impervious membrane disposed in the path of the transmitted acoustic signal and the reflected acoustic signal, between the sensor housing and the base, to isolate the acoustic transmitter, the acoustic receiver, and the electrical circuit from the liquid, and vapors from the liquid, disposed in the tank.
  4. 25. A time-domain reflectometer that measures the level of a liquid in a tank, comprising:a base having a lower opening and side-by-side upper openings communicating with the lower opening;means for securing the base to a wall of the tank, with the lower opening of the base being exposed to the interior of the tank;a liquid- and vapor-impervious membrane disposed across the side-by-side upper openings of the base, to seal the openings and prevent the exit through the openings of any liquid or vapor disposed in the tank;an acoustic transmitter aligned with a first of the side-by-side upper openings of the base and configured to transmit an acoustic signal into the tank, via the lower opening, whereupon the acoustic signal is reflected from the surface of such liquid;an acoustic receiver aligned with a second of the side-by-side upper openings of the base and configured to receive the reflected acoustic signal, via the lower opening; andan electrical circuit that measures the time delay from the time the acoustic transmitter transmits the acoustic signal until the time the acoustic receiver receives the reflected acoustic signal, to produce a time delay measurement that represents the level of the liquid in the tank.

References Cited

U.S. Patent Documents

Document NumberAssigneesInventorsIssue/Pub Date
US4000650 Bindicator Company Snyder Jan 1977
US4145914 Jack A. Perry Newman Mar 1979
US4170765 Marvtek, Corporation Austin et al. Oct 1979
US4264788 Princo Instruments, Inc. Keidel et al. Apr 1981
US4596144 Canadian Corporate Management Co., Ltd. Panton et al. Jun 1986
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US4984449 Caldwell System Corp. Caldwell et al. Jan 1991
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Foreign Patent Documents

Document NumberAssigneesInventorsIssue/Pub Date
WO20WO9105226Apr 1991
WO20WO9519559Jul 1995

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