Resonant tube level sensor
First Claim
1. A level detector for determining whether a material has reached a sensing position, said level detector comprising:
- a tube having a first end for locating at a sensing position and a second end;
a transducer at said second end;
a driver for driving said transducer at a first frequency for a time that is sufficient to produce resonance in said tube;
a decay sensor for producing a level signal that indicates whether the material has reached the sensing position, wherein said level signal depends on whether said first frequency produced resonance in said tube, wherein said resonance depends on whether the material has reached the sensing position, and wherein said decay sensor monitors the decay of said first frequency in said tube to determine if resonance was produced.
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Accused Products
Abstract
Acoustic level sensing by creating, or failing to create, resonance in a tube having a free end. An acoustic transducer at one end of the tube injects sound at a frequency that could produce resonance, depending on whether the free end is open or closed. The drive to the acoustic transducer is then removed, and the sound decay in the tube is monitored to determine if resonance occurred. Based on that determination, a signal is produced that indicates whether a material has or has not closed the free end of the tube. Beneficially, the same acoustic transducer that produces the sound monitors the sound decay. To determine whether resonance has occurred, or to verify system operation, the sound decay at the possible resonant frequency can be compared to the decay at another frequency. Temperature compensation can be performed by attempting to produce resonance at a plurality of frequencies.
19 Citations
20 Claims
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1. A level detector for determining whether a material has reached a sensing position, said level detector comprising:
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a tube having a first end for locating at a sensing position and a second end;
a transducer at said second end;
a driver for driving said transducer at a first frequency for a time that is sufficient to produce resonance in said tube;
a decay sensor for producing a level signal that indicates whether the material has reached the sensing position, wherein said level signal depends on whether said first frequency produced resonance in said tube, wherein said resonance depends on whether the material has reached the sensing position, and wherein said decay sensor monitors the decay of said first frequency in said tube to determine if resonance was produced. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A level detector for determining whether a material has reached a sensing position, said level detecting apparatus comprising:
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a tube having a first end for locating at a sensing position and a second end;
a transducer at said second end;
a driver for driving said transducer at a plurality of frequencies in an attempt to produce resonance in said tube, wherein said transducer is driven at each frequency of said plurality of frequencies for a time sufficient to produce resonance;
a decay sensor for producing a level signal that indicates whether the material has reached the sensing position, wherein said level signal depends on whether resonance was produced in said tube, wherein said resonance depends on whether the material has reached the sensing position, and wherein said decay sensor monitors the decay in said tube of at least one frequency of said plurality of frequencies to determine if resonance was produced. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14)
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15. A method of determining whether a material has reached a sensing position, comprising the steps of:
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locating the first end of a tube at a sensing position;
injecting sound waves having a first frequency into the tube cavity for a period of time that is sufficient to produce resonance in the tube; and
determining whether the material has reached the sensing position by sensing whether resonance was produced in the tube, wherein resonance is sensed by monitoring the sound decay in the tube of the sound waves having the first frequency. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification