Dynamic volumetric instrument gauge
First Claim
1. An instrument for measuring the volume of an incompressible fluid in at least one liquid container or tank, comprising:
- means for vibrating the tank at its structural resonant frequency as a function of the mass of the liquid in the tank;
means for measuring the dynamic structural resonant frequency of the tank and liquid load;
means for producing dynamic electrical resonance signals indicative of said structural resonant frequency and for filtering out noise frequencies;
means for translating said dynamic electrical resonance signals into signals indicative of the liquid volume in said tank; and
means electrically connected to said translating means for displaying the volume of said liquid in said tank in response to said volume indicating signals;
whereby the volume of liquid remaining in the tank is displayed on said display with an accuracy that is immune to acoustic noise and an accuracy that increases as the tank becomes more empty.
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Accused Products
Abstract
This instrument contains a transducer and a sensor that are mounted on the exterior surface of a liquid container or tank. The transducer is tuned by electronic signals to the mechanical resonant frequency of the liquid container or tank. The sensor converts the mechanical vibrations into dynamic electrical signals using electronic components. A phase detector and feedback circuitry force the transducer to track the resonant frequency of the tank as liquid is removed from the tank. The signal output of the feedback control circuitry is converted to display the amount of liquid remaining in the tank. The resonant frequency of the liquid container is a measure of the total mass of the container. This includes the tare weight of the container plus the weight of the liquid in the tank. The tare weight of the tank is a constant. The stiffness of the tank can be considered a constant. The dampening coefficient changes do not adversely effect the accuracy requirements of the instrument. Therefore, the change in resonant frequency of the tank as liquid is removed is nonlinear, but is an analytic function of the liquid remaining in the tank. Zero and span adjustments eliminate the effect of the constants and permit one design to satisfy many requirements. At resonance the amplitude response of the tank is much larger than the noise of the environment. As the intelligence of the instrument to interpret changes in liquid volume is a function of frequency, this adds to the noise immunity. The nonlinear dynamic response of the instrument is an asset in the use of this gauge for fuel tanks and other applications.
51 Citations
16 Claims
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1. An instrument for measuring the volume of an incompressible fluid in at least one liquid container or tank, comprising:
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means for vibrating the tank at its structural resonant frequency as a function of the mass of the liquid in the tank; means for measuring the dynamic structural resonant frequency of the tank and liquid load; means for producing dynamic electrical resonance signals indicative of said structural resonant frequency and for filtering out noise frequencies; means for translating said dynamic electrical resonance signals into signals indicative of the liquid volume in said tank; and means electrically connected to said translating means for displaying the volume of said liquid in said tank in response to said volume indicating signals; whereby the volume of liquid remaining in the tank is displayed on said display with an accuracy that is immune to acoustic noise and an accuracy that increases as the tank becomes more empty. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of measuring the liquid volume in a tank, comprising:
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subjecting said tank, loaded with liquid, to periodic mechanical impulses to cause said tank to vibrate at its structural resonant frequency; measuring the amplitude of said structural resonant vibrations; translating said vibrations at said structural resonant frequency into signals which are in an analytic inverse exponential relationship to the quantity of liquid remaining in the tank; and displaying said liquid volume on a liquid volume indicator; whereby said display of said liquid volume becomes increasingly accurate as said tank empties. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15)
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16. An instrumented liquid holding tank for holding liquid and producing signals indicative of the liquid volume in said tank, comprising:
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a tank made of stiff and rigid material, said tank having an interior wherein said liquid is contained, and an exterior surface; a transducer and a sensor mounted on said exterior surface of said tank; said transducer being responsive to driving signals to vibrate said tank at its structural resonant frequency; and said sensor producing signals indicative of the structural resonant frequency of said tank when vibrated by said transducer; whereby said sensor signals may be translated into signals which are in an analytic inverse exponential relationship to the liquid volume in said tank, and displayed on a display to show the liquid volume remaining in said tank, and said display of said liquid volume becomes increasingly accurate as said tank empties.
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Specification