Method of testing the integrity of an ultrasonic system for sensing liquid-fluid interfaces
First Claim
1. A method for testing the integrity of an ultrasonic system for sensing a liquid-fluid interface in a container, said system comprising:
- (a) first and second crystals, each of said crystals having a relatively high resonant frequency and a relatively low resonant frequency;
(b) a support structure with first and second end arms connected by a cross member, said first crystal being bonded to said first end arm and said second crystal being bonded to said second end arm, said first and second crystals being positioned opposite each other across a gap between said first and second end arms in said container;
(c) means for selectively enabling said first crystal to resonate either at its relatively high resonant frequency or at its relatively low resonant frequency, said relatively high resonant frequency being sufficiently high to cause an ultrasonic signal to be transmitted into said gap without causing appreciable ultrasonic transmission through said cross portion of said support structure, said relatively low resonant frequency being sufficiently low to cause transmission of a detectable ultrasonic signal through said cross member; and
(d) means for detecting resonance induced in said second crystal due to resonance of said first crystal at either its relatively high resonance frequency or its relatively low resonance frequency;
said testing method comprising the steps of causing said first crystal to resonate at its relatively low resonant frequency irrespective of whether the liquid-fluid interface lies within said gap in order to cause ultrasonic transmission through said cross member, and detecting resonance in said second crystal at said relatively low resonant frequency, thereby indicating that the ultrasonic system is operational.
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Accused Products
Abstract
An ultrasonic system for sensing a liquid-fluid interface comprises a support structure (10) to which a transmitting crystal (21) and a receiving crystal (22) are bonded in such a way that the crystals (21 and 22) are positioned opposite each other across a gap (30). Each of the crystals (21 and 22) has a relatively high resonant frequency and a relatively low resonant frequency. An amplifier means (40) and a bandpass filter means (50) are connected to the crystals (21 and 22) to form a feedback loop. In normal operation, the transmitting crystal (21) is excited to resonate at its high resonant frequency in order to cause transmission of an ultrasonic signal across the gap (30) without causing appreciable ultrasonic transmission through the support structure (10) to the receiving crystal (22). When it is desired to test the system for integrity in the absence of liquid in the gap (30), the transmitting crystal (21) is excited to resonate at its low resonant frequency and the passband of the bandpass filter means (50) is shifted to enable low frequency oscillations to occur in the feedback loop due to ultrasonic transmission (i.e., cross-talk) through the support structure (10) between the crystals (21 and 22).
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Citations
10 Claims
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1. A method for testing the integrity of an ultrasonic system for sensing a liquid-fluid interface in a container, said system comprising:
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(a) first and second crystals, each of said crystals having a relatively high resonant frequency and a relatively low resonant frequency; (b) a support structure with first and second end arms connected by a cross member, said first crystal being bonded to said first end arm and said second crystal being bonded to said second end arm, said first and second crystals being positioned opposite each other across a gap between said first and second end arms in said container; (c) means for selectively enabling said first crystal to resonate either at its relatively high resonant frequency or at its relatively low resonant frequency, said relatively high resonant frequency being sufficiently high to cause an ultrasonic signal to be transmitted into said gap without causing appreciable ultrasonic transmission through said cross portion of said support structure, said relatively low resonant frequency being sufficiently low to cause transmission of a detectable ultrasonic signal through said cross member; and (d) means for detecting resonance induced in said second crystal due to resonance of said first crystal at either its relatively high resonance frequency or its relatively low resonance frequency; said testing method comprising the steps of causing said first crystal to resonate at its relatively low resonant frequency irrespective of whether the liquid-fluid interface lies within said gap in order to cause ultrasonic transmission through said cross member, and detecting resonance in said second crystal at said relatively low resonant frequency, thereby indicating that the ultrasonic system is operational. - View Dependent Claims (2, 3, 4)
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5. An ultrasonic system for sensing a liquid-fluid interface in a container, said system comprising:
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(a) first and second crystals, each of said crystals having a relatively high resonant freqency and a relatively low resonant frequency; (b) a support structure to which said first and second crystals are bonded, said support structure being configured so that said first and second crystals are positioned opposite each other across a gap in said container; (c) amplifier means and bandpass filter means connected to said first and second crystals so as to form a feedback loop; (d) means for exciting said first crystal to resonate selectively at said high and low resonant frequencies, said high frequency being sufficiently high to cause an ultrasonic signal to be transmitted across said gap without causing appreciable ultrasonic transmission through said support structure to said second crystal when said liquid-fluid interface lies within said gap, said low frequency being sufficiently low to cause appreciable ultrasonic transmission to said second crystal through said support structure; (e) switching means for causing said first crystal to resonate at said high frequency and for establishing an operating passband for said bandpass filter means to enable high-frequency oscillations to occur in said feedback loop when said liquid-fluid interface lies within said gap, and means coacting with said switching means for causing said first crystal to resonate at said low frequency and for establishing a testing passband for said bandpass filter means to enable low-frequency oscillations to occur in said feedback loop when said liquid-fluid interface does not lie within said gap, thereby indicating that the integrity of the ultrasonic system is operational. - View Dependent Claims (6, 7, 8, 9, 10)
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Specification