Surface Acoustic Wave Sensor Clamping for Creep-Free Force Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing surface acoustic wave sensors face challenges with long-term stability and sensitivity issues when adhesive connections are used to measure force, as they can lead to creep effects and non-constant sensitivity, especially when the measuring body deforms.
Innovation Solution
A surface acoustic wave sensor is clamped using a prestressing device that applies a uniaxial prestressing force in the main direction of wave propagation, eliminating the need for adhesive connections and allowing for precise control of sensitivity by adjusting the prestress level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adhesive connection is used to couple the sensor to the measuring body, then the sensor can be mounted on the body, but long-term stability deteriorates due to creep effects
Solution Approach 1:
The adhesive connection is completely removed from the system. The sensor substrate is coupled directly to the measuring body through a mechanical connection element that provides form-fit connection, eliminating the adhesive layer and its associated creep problems.
Solution Approach 2:
A mechanical connection element is introduced as an intermediary between the sensor substrate and the measuring body. This element provides a stable, creep-free mechanical connection that transfers forces reliably over long periods.
2Measurement precision
If adhesive connection is used, then the sensor can be mounted on the body, but sensitivity becomes non-constant and increases with body expansion
Solution Approach 1:
The adhesive connection is removed to eliminate the cause of non-constant sensitivity. The direct mechanical coupling ensures that the sensor substrate deforms proportionally with the measuring body, maintaining constant sensitivity throughout the measurement range.
3Measurement precision
If the sensor substrate is thicker and less elastic, then the substrate provides structural stability, but the sensitivity at low deformations decreases
Solution Approach 1:
The sensor substrate is designed with different properties in different regions. The substrate thickness and material properties are optimized locally to provide sufficient structural stability while maintaining high elasticity and sensitivity in the measurement region where deformation occurs.
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 approach enhances the accuracy of force measurement by shifting the operating point to a higher sensitivity range, ensuring reliable and long-term stable force transmission without the drawbacks of adhesive coupling, such as creep and reduced sensitivity at low deformations.
Implementation Method 1
They essentially consist of a piezoelectric substrate and interdigital electrodes arranged on its surface, through which surface acoustic waves can be excited or reflected in the substrate when an electrical signal is fed in.
Implementation Method 2
Environmental influences such as a change in temperature or deformation of the substrate as a result of the application of a force change the wave propagation properties.
Data Source
Figure 1~2
Figure 3~4
AI summary
The device has a surface wave sensor (1) provided with a piezoelectric substrate (2), where acousto-electric transducers (3) i.e. interdigital electrodes, are arranged on a surface of the substrate. The substrate of the surface wave sensor is pressurized with a uniaxial bias force in a main propagation direction (H) of surface waves by a biasing device. The biasing device is arranged in or at a measuring body such that force is transferred to the substrate along the biasing force of the biasing device. Clamping bodies are supported at the measuring body at surfaces of a cavity.