Fluid flow measuring apparatus
First Claim
1. Fluid flow measuring apparatus comprising:
- means to generate an electrical carrier signal;
means to generate a modulation signal;
means to frequency modulate the carrier signal in accordance with the modulation signal;
first and second transducers which are spaced-apart along the fluid flow;
means to feed the modulated carrier signal to one of said transducers so that said transducer transmits ultrasonic energy through the fluid to be received by the other transducer;
a phase-locked loop to maintain a fixed relationship between the phase of the modulation fed to the transmitting transducer and the phase of the modulation received by the receiving transducer by adjustment of the frequency of said modulation signal; and
means responsive to said frequency of said modulation signal to indicate speed of fluid flow.
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Accused Products
Abstract
Fluid flow measuring apparatus comprises two ultrasonic transducers (1, 2) between which an ultrasonic energy beam is transmitted through the fluid. The beam is frequency modulated (4, 5) by an audio signal, and the relationship between the frequency or phase of the received modulation signal (6, 7, 8) and that of the transmitted modulation signal gives a measure (10) of the speed of flow of the fluid. Beams of ultrasonic energy are preferably fed in two mutually opposite directions, for example by switching (3) the transducers to act alternately as transmitter and receiver, and the measurement is computed from the two relationships. An anemometer (FIG. 7) comprises two such systems arranged to produce mutually perpendicular ultrasonic beams, and a computer (25) to compute wind speed (28) and direction (29) from the frequency or phase relationships.
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Citations
7 Claims
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1. Fluid flow measuring apparatus comprising:
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means to generate an electrical carrier signal; means to generate a modulation signal; means to frequency modulate the carrier signal in accordance with the modulation signal; first and second transducers which are spaced-apart along the fluid flow; means to feed the modulated carrier signal to one of said transducers so that said transducer transmits ultrasonic energy through the fluid to be received by the other transducer; a phase-locked loop to maintain a fixed relationship between the phase of the modulation fed to the transmitting transducer and the phase of the modulation received by the receiving transducer by adjustment of the frequency of said modulation signal; and means responsive to said frequency of said modulation signal to indicate speed of fluid flow. - View Dependent Claims (2, 3, 4, 5, 6)
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7. Fluid flow measuring apparatus comprising:
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means to generate a first electrical carrier signal; means to generate a first modulation signal; means to frequency modulate said first carrier signal in accordance with said first modulation signal; means to generate a second electrical carrier signal having a different frequency from said first electrical carrier signal; means to generate a second modulation signal; means to frequency modulate said second carrier signal in accordance with said second modulation signal; first and second transducer means which are spaced-apart along the fluid flow; means to feed the frequency modulated first carrier signal to said first transducer means so that said first transducer continuously transmits ultrasonic energy through the fluid to be received by said second transducer means; means to feed the frequency modulated second carrier signal to said second transducer means so that said second transducer means continuously transmits ultrasonic energy through the fluid to be received by said first transducer means; a first phase-locked loop to maintain a fixed relationship between the phase of the modulation at said first transducer means and the phase of the received modulation at said second transducer means by adjustment of the frequency of said first modulation signal; a second phase-locked loop to maintain a fixed relationship between the phase of the modulation at said second transducer means and the phase of the received modulation at said first transducer means by adjustment of the frequency of said second modulation signal; and means responsive to the relationship between the frequencies of said first and second modulation signals to indicate the speed of fluid flow.
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Specification