Ultrasonic flow meter
First Claim
1. A method of measuring a mean time of flight for an ultrasonic signal to travel a given distance in a fluid under zero flow conditions, independent of the rate of flow, if any, of said fluid during said measurement, comprising:
- Driving a periodic input signal through first and second ultrasonic transducers simultaneously to generate first and second transmitted ultrasonic signals, respectively;
While driving said transducers with said input signal, receiving with said first transducer said second transmitted signal, and receiving with said second transducer said first transmitted signal, and measuring a phase relationship between said first received signal and said second received signal, said phase relationship defining a difference signal;
Computing said time of flight by dividing the distance between said transducers by the time elapsed between a selected number of cycles of said difference signal, said selected number of cycles corresponding to a frequency of said input signal and the distance between said transducers.
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Accused Products
Abstract
A method and apparatus utilizing a pair of ultrasonic transducers simultaneously transmitting and receiving to measure the mean time of flight of an ultrasonic signal over a given distance, and thereby the speed of sound of a fluid in a conduit at a given temperature, independent of flow rate, and the flow rate of the fluid. A signal source simultaneously drives an upstream transducer and a downstream transducer, each of which receive the signal transmitted by the other. The difference between the upstream and downstream signals takes into account the speed of sound of the fluid. The time of flight for the upstream and downstream signals can then be used to calculate the flow rate. A phase locked loop coupled to the signal source automatically adjusts for variations of the speed of sound in the fluid in response to temperature changes.
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Citations
15 Claims
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1. A method of measuring a mean time of flight for an ultrasonic signal to travel a given distance in a fluid under zero flow conditions, independent of the rate of flow, if any, of said fluid during said measurement, comprising:
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Driving a periodic input signal through first and second ultrasonic transducers simultaneously to generate first and second transmitted ultrasonic signals, respectively; While driving said transducers with said input signal, receiving with said first transducer said second transmitted signal, and receiving with said second transducer said first transmitted signal, and measuring a phase relationship between said first received signal and said second received signal, said phase relationship defining a difference signal; Computing said time of flight by dividing the distance between said transducers by the time elapsed between a selected number of cycles of said difference signal, said selected number of cycles corresponding to a frequency of said input signal and the distance between said transducers. - View Dependent Claims (2, 3, 4, 5)
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6. A method of measuring a flow of fluid in a conduit comprising:
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Driving an input signal through first and second ultrasonic transducers simultaneously to generate a first and second transmitted ultrasonic signal, respectively; While driving said transducers with said input signal, receiving with said first transducer said second transmitted signal, and receiving with said second transducer said first transmitted signal; Measuring a difference between said first and second received signals, said difference defining a difference signal and being directly proportional to fluid flow through said pipe, wherein said input signal is derived from said difference signal; and Adjusting a frequency of said input signal to maintain a selected number of cycles of said difference signal between said transducers, wherein the distance between said transducers corresponds to an integral number of half cycles of said difference signal. - View Dependent Claims (7, 8)
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9. A method of measuring a mean time of flight for an ultrasonic signal to travel a given distance in a fluid under zero flow conditions, independent of a rate of flow, if any, of said fluid during said measurement, comprising:
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Driving a periodic input signal through a first ultrasonic transducer to generate a first transmitted ultrasonic signal and receiving with a second transducer said first transmitted signal; Driving said periodic input signal through said second ultrasonic transducer to generate a second transmitted ultrasonic signal and receiving with said first transducer said second transmitted signal; Measuring a phase relationship between said first received signal and said second received signal, said phase relationship defining a difference signal; Computing said time of flight by dividing the distance between said transducers by a time elapsed between a selected number of cycles of said difference signal, said selected number of cycles corresponding to a frequency of said input signal and the distance between said transducers. - View Dependent Claims (10, 11, 12, 13, 14, 15)
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Specification