Measuring and testing – Vibration – By mechanical waves
Patent
1992-02-07
1994-11-01
Chapman, John E.
Measuring and testing
Vibration
By mechanical waves
73 32A, 73644, 73 6453, G01N 2918, G01N 924
Patent
active
053598970
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for determining the time taken for sound energy to cross a body of fluid in a pipe.
2. Related Art
The time taken for sound energy to cross a body of fluid in a pipe of known linear dimension in the direction of propagation of the sound energy provides a measure of the speed of sound in the fluid, and that can be used to determine a parameter of the fluid in the pipe, for example, the density of the fluid in the pipe. The determination of a parameter of a fluid may permit the identification of the fluid. For example, a measure of the speed of sound in a fluid which may be either beer or water may be used to distinguish between the fluids. Therefore, an apparatus for classifying fluids may be, in effect, an apparatus for measuring the speed of sound in the fluid.
BRIEF SUMMARY OF THE INVENTION
In accordance with the present invention, an apparatus for determining the time taken for sound energy to cross a body of fluid in a pipe includes a first electro-acoustic transducer which, in operation, sends sound energy through fluid in the pipe, a second electroacoustic transducer which, in operation, receives sound energy that has passed from the first electro-acoustic transducer through the fluid, electrical means for energising the first electro-acoustic transducer, and means for determining the difference between the time at which the first electro-acoustic transducer is energised and the time at which an electrical signal comes from the second electro-acoustic transducer in response to the transmitted acoustic signal, wherein the electro-acoustic transducers lie against respective substantially flat members which are positioned on opposite sides of the pipe and are substantially parallel to each other, which substantially flat members seal respective apertures in the pipe, wherein pipe material around each aperture curves away from the centre of the pipe towards the periphery of the aperture and contacts the respective substantially flat member along the entire periphery of the aperture.
Preferably, the pipe material around each aperture has a form generated by the forcing of a ball of hard material through a pilot opening in the pipe. It has been found that the curvature of the periphery of each aperture produced by the operation of forcing a ball of hard material through a pilot opening in the pipe is consistent with highly acceptable levels of noise from the flow of fluid past the aperture.
It has been found that the material around each aperture has a radius of curvature of the order of 1/2 inch, as a result of the operation for producing the aperture.
Preferably, the apertures are centred on a common diameter of the pipe.
Preferably, the means for determining the difference between the time at which the first electro-acoustic is energised and the time at which an electrical signal comes from the second electro-acoustic transducer, in response to the transmitted acoustic signal, includes delay means providing an electrical path with a delay equal to the interval between successive pulses from pulse generating means which energises the first electroacoustic transducer, and means for detecting when the leading edge of a pulse which passes through the delay means leaves the delay means before an electrical signal comes from the second electro-acoustic transducer.
Preferably, the apparatus includes means for setting the pulse generating means to its lowest frequency when the leading edge of a pulse which passes through the delay means leaves the delay means before an electrical signal comes from the second electro-acoustic transducer.
Preferably, the apparatus includes means for selecting a further electrical signal which comes from the second electro-acoustic transducer and is produced by sound energy which reaches the second electro-acoustic transducer after being reflected between the first and second electro-acoustic transducers, means for measuring the amplitude of the second electrical signal, and mea
REFERENCES:
patent: 2708366 (1955-05-01), Blocher et al.
patent: 2768524 (1956-10-01), Beard
patent: 3468157 (1969-09-01), Burk et al.
patent: 4004461 (1977-01-01), Lynnworth
patent: 4015464 (1977-04-01), Miller et al.
patent: 4255964 (1981-03-01), Morison
Hamstead Peter J.
Smith Alan C.
Chapman John E.
Front Engineering Ltd.
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