Velocity measurement system
First Claim
1. A fluid flow velocity measurement system comprising:
- acoustic emission means for transmitting an acoustic signal of a discrete frequency into a volume of moving fluid;
acoustic reception means including a transducer positioned to receive a plurality of Doppler shifted signals related to said acoustic signal from fluid borne objects, and said Doppler shifted signals being received over a discrete time and comprising a time domain signal train;
frequency domain translation means responsive to said time domain signal train for translating it to a plurality of frequency domain signals;
frequency selection means for selecting a frequency signal from said frequency domain signals; and
velocity computation means responsive to said frequency selection means for providing as an output a signal representative of an average velocity of said fluid flow, being a velocity related to a frequency from said frequency signals less than the highest fluid velocity present.
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Abstract
A sonic-type fluid flow measuring system wherein reflections or echoes of an ultrasonic acoustic emitter are sensed and typically comprise a number of frequencies representative of a number of discrete velocities of flow in a volume of fluid. As a sample, they simply appear as a voltage plot as a function of time and wherein the time width of a given signal excursion relates to the frequency of a given signal. Thereafter, this time domain signal sample is converted to a frequency domain sample whereby the presence and magnitude of each frequency component, or velocity component, is isolated, this being typically done by what is known as a Fast Fourier Transform. The highest frequency, velocity, signal from each of a rapid succession of samples is then obtained and stored in a memory. The highest and lowest of these are then discarded, and the remaining are averaged to obtain more likely representations of velocity. As the goal is to determine an average fluid velocity for a whole cross section of fluid flow, the measured peak velocity is a detected reference from which a lesser velocity, for example, 0.9, of it is chosen. To achieve a value for volume of flow, the average velocity is then multiplied by the cross-sectional area of the containment through which flow occurs.
30 Citations
9 Claims
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1. A fluid flow velocity measurement system comprising:
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acoustic emission means for transmitting an acoustic signal of a discrete frequency into a volume of moving fluid; acoustic reception means including a transducer positioned to receive a plurality of Doppler shifted signals related to said acoustic signal from fluid borne objects, and said Doppler shifted signals being received over a discrete time and comprising a time domain signal train; frequency domain translation means responsive to said time domain signal train for translating it to a plurality of frequency domain signals; frequency selection means for selecting a frequency signal from said frequency domain signals; and velocity computation means responsive to said frequency selection means for providing as an output a signal representative of an average velocity of said fluid flow, being a velocity related to a frequency from said frequency signals less than the highest fluid velocity present. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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Specification