Ultrasonic continuous wave particle monitor
First Claim
1. Apparatus for sensing particles in a fluid medium comprising:
- an ultrasonic resonator cavity for containing a fluid medium;
first transducer means on one side of the cavity for continuously propagating thereacross ultrasonic compressional waves whose phase and amplitude are perturbed by the presence of particles in the fluid medium;
second transducer means positioned on the opposite side of the cavity from the first transducer means substantially parallel to and in registry therewith for receiving the ultrasonic waves and converting them to rf electric waves of the same frequency and whose phases and amplitudes are modulated in response to any perturbations in the ultrasonic waves;
means for amplifying the rf waves;
feedback means for applying the amplified rf waves to the first transducer means thereby to establish a self-excited continuous wave oscillatory circuit;
attenuation means in the circuit for causing its operation to be marginally oscillatory whereby small changes in the amplitude of the rf waves caused by any perturbations in the ultrasonic waves produce relatively large changes in the amplitude thereof; and
detection means responsive to perturbations in the rf wave for demodulating the amplified rf wave to produce signals indicative of the presence of particles in the fluid medium whereby enhanced sensitivity to small changes in the ultrasonic properties of the fluid medium caused by the presence of particles therein is achieved.
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Abstract
Apparatus for sensing particles in a fluid medium comprising an ultrasonic resonant cavity for containing a fluid medium. A first transducer on one side of the cavity continuously propagates thereacross ultrasonic compressional waves whose phase and amplitude are perturbed by the presence of particles in the fluid medium. A second transducer positioned on the opposite side of the cavity from the first transducer substantially parallel to and in registry therewith receives the ultrasonic waves and converts them to rf electric waves of the same frequency, the rf electric waves having their phases and amplitudes modulated in response to any perturbations in the ultrasonic waves. The rf waves are amplified and fedback to the first transducer thereby to establish an oscillatory circuit. An attenuator in the oscillatory circuit causes its operation to be marginally oscillatory whereby small changes in the amplitude of the rf waves caused by any perturbations in the ultrasonic waves produce relatively large changes in the amplitude thereof. A detector responsive to perturbations in the rf wave demodulates the amplified rf wave to produce signals indicative of the presence of particles in the fluid medium. Thus, enhanced sensitivity to small changes in the ultrasonic properties of the fluid medium caused by the presence of particles therein is achieved.
62 Citations
18 Claims
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1. Apparatus for sensing particles in a fluid medium comprising:
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an ultrasonic resonator cavity for containing a fluid medium; first transducer means on one side of the cavity for continuously propagating thereacross ultrasonic compressional waves whose phase and amplitude are perturbed by the presence of particles in the fluid medium; second transducer means positioned on the opposite side of the cavity from the first transducer means substantially parallel to and in registry therewith for receiving the ultrasonic waves and converting them to rf electric waves of the same frequency and whose phases and amplitudes are modulated in response to any perturbations in the ultrasonic waves; means for amplifying the rf waves; feedback means for applying the amplified rf waves to the first transducer means thereby to establish a self-excited continuous wave oscillatory circuit; attenuation means in the circuit for causing its operation to be marginally oscillatory whereby small changes in the amplitude of the rf waves caused by any perturbations in the ultrasonic waves produce relatively large changes in the amplitude thereof; and detection means responsive to perturbations in the rf wave for demodulating the amplified rf wave to produce signals indicative of the presence of particles in the fluid medium whereby enhanced sensitivity to small changes in the ultrasonic properties of the fluid medium caused by the presence of particles therein is achieved. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method of sensing discrete particles in a fluid medium comprising:
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continuously generating by a first transducer ultrasonic compressional waves in an ultrasonic resonator cavity having a second transducer means positioned on the opposite side of the cavity from the first transducer; converting the ultrasonic waves received by the second transducer into rf electric waves of the same frequency; amplifying the rf electric waves for feedback to the first transducer to establish a self-excited oscillatory resonant circuit; attenuating the amplified rf waves to make said circuit marginally oscillatory; causing the phase and amplitude of the compressional waves to be perturbed by passing particles through the ultrasonic resonator cavity containing the fluid medium, the phases and amplitudes of the rf electric waves being modulated in response to such perturbations in the ultrasonic compressional waves with the small changes in the amplitude of rf waves resulting from said perturbations causing an increase in amplification gain by marginal oscillatory action thereby to maintain the circuit in oscillation; and
detecting the modulated amplified rf waves to produce signals responsive to the perturbations in the rf waves and indicative of the presence of discrete particles in the fluid medium whereby enhanced sensitivity to small changes in the ultrasonic properties of the fluid medium caused by the presence of particles therein is achieved. - View Dependent Claims (16, 17, 18)
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Specification