Thermal pulsed ultrasonic flow sensor
First Claim
1. A flow meter for measuring the rate of flow of a fluid characterized by an acoustic property that varies with temperature, the flow meter comprising:
- a thermal input means, operable when the fluid is flowing along a flow direction, to provide a bolus of the fluid at a first selected location, the bolus having a temperature different from the rest of the fluid so that the acoustic property of the bolus is different from the acoustic property of the rest of the fluid, the thermal input means further operable to provide a thermal pulse timing signal to a logic circuit for calculating the flow rate; and
at least one acoustic portion, each comprising at least one respective ultrasonic transducer and a respective receiver circuit, each acoustic portion operable, when the fluid is flowing;
to define at least one respective acoustic beam extending transverse to the flow direction at a respective selected location downstream from the first selected location; and
to output from the respective receiver circuit a bolus detection signal responsive to the difference in the acoustic property associated with passage of the bolus to the logic circuit.
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Accused Products
Abstract
In thermal pulse flow measurements a relatively small bolus of flowing fluid is heated or cooled and the time required for the bolus to move downstream a known distance is measured. In many fluids, changing the temperature changes the acoustic transmission properties of the bolus from those of the rest of the fluid, so the bolus can be detected when it intersects an acoustic beam. The use of an acoustic beam or beams, which are usually defined between acoustic transmitting receiving transducers, typically provides a high frequency carrier which is modulated by the change in acoustic properties of the bolus when it passes between the two transducers. When compared to conventional thermal measurements, this acoustic approach provides faster response times and can thus be used for measuring higher flow rates.
65 Citations
20 Claims
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1. A flow meter for measuring the rate of flow of a fluid characterized by an acoustic property that varies with temperature, the flow meter comprising:
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a thermal input means, operable when the fluid is flowing along a flow direction, to provide a bolus of the fluid at a first selected location, the bolus having a temperature different from the rest of the fluid so that the acoustic property of the bolus is different from the acoustic property of the rest of the fluid, the thermal input means further operable to provide a thermal pulse timing signal to a logic circuit for calculating the flow rate; and at least one acoustic portion, each comprising at least one respective ultrasonic transducer and a respective receiver circuit, each acoustic portion operable, when the fluid is flowing; to define at least one respective acoustic beam extending transverse to the flow direction at a respective selected location downstream from the first selected location; and to output from the respective receiver circuit a bolus detection signal responsive to the difference in the acoustic property associated with passage of the bolus to the logic circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of measuring a rate of flow of a fluid along a flow direction, the fluid characterized by an acoustic property that varies with temperature, the method comprising the steps of:
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a) providing a fluid bolus having a temperature different from that of the rest of the fluid at a first location and a first time so as to change the acoustic property of the fluid in the bolus; b) providing at least one acoustic beam transverse to the flow direction at a respective selected distance downstream from the first location; c) conveying the bolus, by means of the flowing fluid, through each acoustic beam; d) determining, by means of circuitry responsive to the changed acoustic property of the fluid in the bolus, a respective time at which the bolus intersects the respective acoustic beam; e) calculating the rate of flow from one of; i) a distance between the first location and one of the acoustic beams and a measured time interval between the first time and the respective time at which the bolus intersects the respective beam, and ii) a distance between two of the beams and a measured interval between the respective times at which the bolus intersects each of the two of the beams. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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Specification