Plate-mode ultrasonic structure including a gel

摘要

An ultrasonic structure which has a thin planar sheet of material forming a Lamb wave propagation medium The propagation medium is coated with a gel. The structure may also include 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 can be included 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.