Elastic wave sensing system
First Claim
1. An acoustic measurement system for measuring a characteristic of material contacting a sheet, the sheet having first and second sides, said system comprisingmeans defining a sensing path extending across a region in the sheettransducer means mounted on the first side of the sheet for generating and sensing elastic wave energy signals propagated along the sensing pathprocessing means for processing the signals to determine variations in signal propagation of said elastic wave energy signals wherein the variations depend on the characteristic of material contacting the second side of the sheet, andreference means for temporarily establishing a surface load reference condition on the first side in said region of the sheet, said processing means determining the signal propagation during said temporary surface load reference condition to identify said variations indicative of the characteristic.
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Accused Products
Abstract
A sensing system detects elastic waves propagated along a sensing path in a sheet to detect a characteristic of material contacting the other side of the sheet. An acoustic load applied between transducers discriminates characteristics in diverse environments. Different systems detect density, stiffness, presence, degree of coupling, thickness, or fill height of the material, with applications to areas as diverse as aircraft wing ice measurement, storage tank fill height detection, and mass flow detection. In one preferred embodiment a protective housing covers and protects the first side of the sheet over a region of the sheet encompassing the sensing path, and may secure transducers in defined positions. The housing preferably defines a closed reservoir that is temporarily filled to determine a normative measurement such as transit time or change in phase velocity. The normative measurement provides an empirical calibration that, in turn, allows a final parameter or a detection threshold to be precisely determined.
62 Citations
21 Claims
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1. An acoustic measurement system for measuring a characteristic of material contacting a sheet, the sheet having first and second sides, said system comprising
means defining a sensing path extending across a region in the sheet transducer means mounted on the first side of the sheet for generating and sensing elastic wave energy signals propagated along the sensing path processing means for processing the signals to determine variations in signal propagation of said elastic wave energy signals wherein the variations depend on the characteristic of material contacting the second side of the sheet, and reference means for temporarily establishing a surface load reference condition on the first side in said region of the sheet, said processing means determining the signal propagation during said temporary surface load reference condition to identify said variations indicative of the characteristic.
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15. An acoustic sensing system for determining a characteristic of a medium contacting a solid wall said system comprising
a transmitting transducer secured to one side of the wall for launching a flexural wave therein, wherein said one side is remote from a side contacting the medium a receiving transducer secured to said one side and spaced from said transmitting transducer for detecting the flexural wave traveling in said wall from the transmitting transducer and producing a signal indicative thereof an interval processor for determining a flexural wave transit time measurement, wherein the transmitting transducer launches a lowest order asymmetric flexural wave such that the signal produced by the receiving transducer is well-defined along a saled signal path, and means responsive to said transit time measurement for determining the characteristic of the medium.
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21. An acoustic measurement system for measuring a characteristic of material contacting a sheet, the sheet having opposed first and second sides, said system comprising
means defining a sensing path extending across a region in the sheet a pair of transducers mounted on the first side of the sheet for generating and sensing elastic wave energy signals propagated along the sensing path processing means for processing the signals to determine the characteristic of material contacting the second side of the sheet, and cover means placed over the first side of the sheet over the region of the sensing path for providing a reference surface loading condition of said first side wherein the signals propagated along said path are processed to develop a reference timing interval, and said processing means processes a received signal in relation to said reference timing interval, that varies with contact of material on the second side.
Specification