Methods for liquid measurement using quasi-static reference subsystem

• US 5,127,266 A
• Filed: 09/19/1990
• Issued: 07/07/1992
• Est. Priority Date: 09/19/1990
• Status: Expired due to Term

• Current Assignee: Vista Research, Inc. (Guidepoint Global LLC)
• Original Assignee: Vista Research, Inc. (Guidepoint Global LLC)
• Inventors: Maresca, Joseph W., Wilson, Christopher P., Starr, James W.
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): GUTIERREZ, DIEGO F
• Application Number:
  US07/585,713
• Time in Patent Office: 657 Days
• Field of Search: 73/290 V, 367/908, 367/108, 367/99, 181/123, 181/124, 181/400, 181/402
• US Class Current: 73/290.00V
• CPC Class Codes: G01F 23/2962 Measuring transit time of reflected waves
• CPC Class Codes: G01F 23/30 by floats
• CPC Class Codes: G01F 23/76 characterised by the construction of the float
• CPC Class Codes: G01M 3/3245 using a level monitoring device G01M3/3272 takes precedence
• CPC Class Codes: Y10S 181/402 Liquid
• CPC Class Codes: Y10S 367/908 Material level detection, e.g. liquid level

Abstract

Methods for measuring liquid levels and leak rates in a storage tank, using an acoustic transducer and a quasi-static reference device that positions an acoustic target within a predetermined distance range below the surface of the liquid. A method for measuring the height of the surface of a liquid, i.e., liquid level. In a tank comprising the steps of (a) positioning the emitting and receiving acoustic transducers below the surface of the liquid, (b) positioning a plurality of fiducials separated by known distances such that at least two of the fiducials lie below the surface of the liquid, (c) emitting acoustic signals, (d) receiving and measuring the travel times for the reflections of the acoustic signals from the liquid surface and the fiducials, (e) estimating the speed of sound in the liquid using the travel times for the acoustic signals in the liquid between at least two of the fiducials, and (f) calculating the height of the liquid surface by multiplying the speed of sound in the liquid by the travel time from the liquid surface to a known height above the bottom of the liquid, and adding the known height to the product of the speed of sound and travel time.

Claims

1. A method for measuring the height of the surface of a liquid, comprising:

(a) positioning acoustic signal means for emitting and receiving acoustic signals below the surface of the liquid;

(b) positioning a plurality of fiducials separated by known distances, such that at least two of said fiducials lie below the surface of the liquid;

(c) emitting acoustic signals from said acoustic signal means;

(d) receiving and measuring the travel times for the reflections of said acoustic signals from the liquid surface and fiducials with said acoustic signal means;

(e) estimating the speed of sound in the liquid using the travel times for the acoustic signals in the liquid between at least two of said fiducials; and

(f) calculating the height of the liquid surface by multiplying said speed of sound in the liquid by the travel time from said liquid surface to a known height above the bottom of the liquid, and adding said known height to the product of said speed of sound and said travel time.

2. The method of claim 1, wherein the step of positioning said plurality of fiducials includes the step of positioning a quasistatic reference device having a plurality of fiducials separated by known distances, such that at least two of said quasi-static reference fiducials lie below the surface of the liquid.

3. The method of claim 1, wherein

(a) the step of positioning said plurality of fiducials includes the step of positioning a plurality of fixed fiducials separated by known distances, such that at least two of said fixed fiducials lie below the surface of the liquid;

(b) the step of positioning said plurality of fiducials includes the step of positioning a quasi-static reference device having a plurality of quasi-fixed fiducials separated by known distances, such that at least two of said quasi-fixed fiducials lie below the surface of the liquid; and

(c) the step of estimating the speed of sound in the liquid includes using the travel times for the acoustic signals in the liquid between at least two of said fixed fiducials and between at least two of said quasi-fixed fiducials.