Ultrasonic Measuring Device Rayleigh Wave Attenuation
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Solution Overview
Problem
Ultrasonic measuring devices face interference from additional Lamb waves or reflections at the outer wall, which complicate signal reception and evaluation due to coupling of ultrasound signals into the measurement chamber wall, leading to energy loss and interference with the intended signal path.
Innovation Solution
The ultrasonic measuring device is designed with a measurement chamber wall configuration that prevents Rayleigh wave excitation by using a dissonant structure with spatially varying acoustic impedances and indentations, ensuring the ultrasound signals are not reflected back into the signal path, thereby reducing interference and energy loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ultrasonic transducers transmit signals through the measurement chamber volume with reflections at the inner wall, then the measurand can be detected, but Rayleigh waves are excited at the outer wall causing interference and energy loss
Solution Approach 1:
The patent converts the harmful Rayleigh wave effect into a beneficial filtering mechanism by designing the outer wall thickness to be at least one Rayleigh wavelength. This thickness condition causes Rayleigh waves to undergo destructive interference and attenuation, while the useful ultrasonic signals passing through the chamber volume are unaffected. The harmful wall-borne waves are thus converted into a filtering mechanism that protects the measurement signal.
Solution Approach 2:
The patent changes the critical parameter of wall thickness to resolve the contradiction. By setting the outer wall thickness to be at least one Rayleigh wavelength (a specific parameter value), the system transforms the wall from a source of interference into a wave-filtering structure. This parameter change selectively attenuates Rayleigh waves while maintaining transmission of the measurement ultrasonic signals.
2Measurement precision
If the measurement chamber wall is made thicker to prevent Rayleigh wave interference, then signal quality improves, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent resolves the contradiction by changing the wall thickness parameter to a specific value (at least one Rayleigh wavelength) rather than using complex active filtering systems. This simple geometric parameter change provides passive Rayleigh wave attenuation without requiring additional components, control systems, or complex manufacturing processes, thus improving signal quality while maintaining device simplicity.
3Measurement precision
If ultrasonic signals are transmitted through the chamber volume, then the measurand detection is achieved, but energy is lost due to Rayleigh wave excitation at the outer wall
Solution Approach 1:
The patent converts the energy loss mechanism into a protective filter by designing the outer wall thickness to be at least one Rayleigh wavelength. This causes Rayleigh waves to undergo destructive interference and energy dissipation within the wall structure, preventing energy from coupling back into the measurement signal. The energy that would have been lost to interference is instead dissipated harmlessly in the wall, improving signal reception accuracy.
Solution Approach 2:
By changing the wall thickness parameter to at least one Rayleigh wavelength, the patent creates a passive energy filtering mechanism. This parameter change causes Rayleigh waves to naturally attenuate through destructive interference, reducing energy loss from wall coupling without requiring additional damping materials or active energy compensation systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration improves signal quality by minimizing the interference from Rayleigh waves and reducing energy loss, allowing for more accurate signal reception and evaluation.
Implementation Method 1
the measurement chamber wall has, in the region of the reflection surface, a maximum wall thickness that is at least a factor of 1.5 and in particular at least a factor of 2, and preferably at least a factor of 2.5, greater than a Rayleigh wavelength, associated with the central frequency, of the ultrasound signal in the measurement chamber wall
Implementation Method 2
the ultrasonic transducers are configured to transmit and receive ultrasonic signals by means of Lamb waves or plate waves in the transition region to Rayleigh waves in the measurement chamber wall
Implementation Method 3
the at least one converter element is a piezoelectric element that is mechanically connected to the measurement chamber
Data Source
AI summary
An ultrasound instrument for detecting a measured value of a medium includes a measurement chamber having a chamber wall and a longitudinal axis; a pair of ultrasound transducers configured to transmit ultrasound signals along a signal path between ultrasound transducers of the pair through the measurement chamber and to receive ultrasound signals, wherein the signal path includes a signal reflection on a reflection surface, wherein the chamber wall in a region of the reflection surface opposite a first chamber side is configured to prevent a reflection of an ultrasound signal on a chamber outer surface of the chamber wall in the direction of the signal path, wherein the chamber wall has, in the region of the reflection surface, a maximum wall thickness which is at least a factor of 1.5 greater than a Rayleigh wavelength, associated with a central frequency, of the ultrasound signal in the chamber wall.