Plate-mode ultrasonic sensor
First Claim
1. An ultrasonic sensor comprising:
- a composite structure comprising (a) a supporting frame of a first material and (b) a propagation medium comprising a thin planar sheet of a second, different material capable of supporting Lamb waves, supported peripherally by said supporting frame, said sheet having a thickness very much thinner than the wavelength of Lamb waves to be propagated thereon and having some physical characteristics determined by the value of a measurand acting thereon, said physical characteristics determining the propagation characteristics of Lamb waves to be propagated along the medium;
electrical means coupled to the thin planar sheet of said propagation medium for producing Lamb waves in the propagation medium;
output means on said sheet for producing an electrical signal representative of the determined propagation characteristics of the Lamb waves propagating along the propagation medium; and
measuring means for measuring selected characteristics of said electrical signal,whereby when said sensor is acted on by a measurand, the physical characteristics of said propagation medium are determined and said electrical signal characteristics are also determined, so that said measuring means indicates the value of the measurand.
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Abstract
An ultrasonic sensor which has a thin planar sheet of material forming a Lamb wave propagation medium, the sheet having a thickness which is no greater than about twenty microns. The sensor also includes a Lamb wave generator for generating Lamb waves in the propagation medium and an output device for producing an electrical signal representative of the propagation characteristics of the Lamb waves propagating along the propagation medium. A measuring device is included in the sensor to measure selected characteristics of the output electrical signal. The propagation medium has some physical characteristics that are determined by the value of a measurand acting on the medium and the determined physical characteristics determine the propagation characteristics of the Lamb waves which are propagated along the medium. When the sensor is acted on by a measurand to determine the physical characteristics of the propagation medium, the characteristics of the electrical signal are also determined. The measuring device measures the electrical signal and provides an indication of the measurand value. Several sensing arrangements are also disclosed as well as methods for making the planar propagation medium.
162 Citations
39 Claims
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1. An ultrasonic sensor comprising:
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a composite structure comprising (a) a supporting frame of a first material and (b) a propagation medium comprising a thin planar sheet of a second, different material capable of supporting Lamb waves, supported peripherally by said supporting frame, said sheet having a thickness very much thinner than the wavelength of Lamb waves to be propagated thereon and having some physical characteristics determined by the value of a measurand acting thereon, said physical characteristics determining the propagation characteristics of Lamb waves to be propagated along the medium; electrical means coupled to the thin planar sheet of said propagation medium for producing Lamb waves in the propagation medium; output means on said sheet for producing an electrical signal representative of the determined propagation characteristics of the Lamb waves propagating along the propagation medium; and measuring means for measuring selected characteristics of said electrical signal, whereby when said sensor is acted on by a measurand, the physical characteristics of said propagation medium are determined and said electrical signal characteristics are also determined, so that said measuring means indicates the value of the measurand. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39)
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Specification