Methods for temperature-compensated liquid height and leak detection measurements using quasi-static reference subsystem
First Claim
1. A method for measuring the temperature-compensated change in the height of a surface of a liquid during a measurement period, comprising:
- (a) positioning acoustic signal means for emitting and receiving acoustic signals below the surface of the liquid;
(b) positioning a quasi-static reference device having at least one fiducial such that at least one fiducial lies within a predetermined range below the surface of the liquid, wherein said reference device may move up or down with changes in the surface level of the liquid but remains fixed to a stationary support during said measurement period;
(c) positioning at least one fiducial below the surface of the liquid to establish points separated by a known distance;
(d) emitting acoustic signals from said acoustic signal means;
(e) receiving and measuring the travel times for the reflections of said acoustic signals from the liquid surface and said fiducials with said acoustic signal means during said measurement period;
(f) calculating changes in said travel times during said measurement period, and using the travel times over said known distance to estimate the speed of sound in the liquid, to correct for temperature-induced changes in said travel times, and to obtain a temperature-compensated change in travel time to said liquid surface; and
(g) calculating the temperature-compensated change in the height of the surface of the liquid during the measurement period using the product of the estimate of the speed of sound in the liquid and said temperature-compensated change in travel time to said liquid surface.
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Abstract
A method for measuring the temperature-compensated change in the height of a surface of a liquid. The method positions an acoustic signal transducer for emitting and receiving acoustic signals below the surface of the liquid, positions a quasi-static reference device with a fiducial such that the fiducial lies within a predetermined range below the surface of the liquid, and positions one or more fiducials below the surface of the liquid to establish points separated by known distances. The transducer emits acoustic signals, and receives their reflections. The travel times of the reflections from the liquid surface and the fiducials are used to calculate changes in travel times during the measurement period, to estimate the speed of sound in the liquid, to correct for temperature-induced changes in the travel times, and to obtain a temperature-compensated change in travel time to the liquid surface. The temperature-compensated change in the height of the surface of the liquid during the measurement period is calculated using the product of the estimate of the speed of sound in the liquid and the temperature-compensated change in travel time to the liquid surface. The presence of a leak in a storage tank may be detected by converting the temperature-compensated change in the height of the surface of the liquid to temperature-compensated volume change using the known shape of the tank and liquid height, and then comparing the temperature-compensated volume change to a threshold value to determine whether the tank is leaking.
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Citations
8 Claims
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1. A method for measuring the temperature-compensated change in the height of a surface of a liquid during a measurement period, comprising:
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(a) positioning acoustic signal means for emitting and receiving acoustic signals below the surface of the liquid; (b) positioning a quasi-static reference device having at least one fiducial such that at least one fiducial lies within a predetermined range below the surface of the liquid, wherein said reference device may move up or down with changes in the surface level of the liquid but remains fixed to a stationary support during said measurement period; (c) positioning at least one fiducial below the surface of the liquid to establish points separated by a known distance; (d) emitting acoustic signals from said acoustic signal means; (e) receiving and measuring the travel times for the reflections of said acoustic signals from the liquid surface and said fiducials with said acoustic signal means during said measurement period; (f) calculating changes in said travel times during said measurement period, and using the travel times over said known distance to estimate the speed of sound in the liquid, to correct for temperature-induced changes in said travel times, and to obtain a temperature-compensated change in travel time to said liquid surface; and (g) calculating the temperature-compensated change in the height of the surface of the liquid during the measurement period using the product of the estimate of the speed of sound in the liquid and said temperature-compensated change in travel time to said liquid surface. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification