Segmented Field Eddy Current Sensor for Dispersive Material Characterization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional eddy-current testing methods face challenges in characterizing materials with dispersive properties, particularly in additive manufacturing processes, where it is difficult to estimate material properties using multi-frequency techniques due to variations in magnetic permeability and conductivity, and the phase shift is often small or not measurable, limiting the ability to distinguish proximity and material properties.
Innovation Solution
The use of segmented field sensors with multiple sensing elements at different spatial wavelengths allows for independent measurement of material properties by exciting the sensor with a single frequency and measuring responses from each element, enabling estimation of proximity and properties like effective permeability without relying on phase shifts or additional simultaneous responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional eddy-current sensing uses single frequency excitation, then the measurement system is simple, but it cannot distinguish between proximity effects and material properties for dispersive materials
Solution Approach 1:
The sensor is divided into multiple sensing elements with different spatial wavelengths, each element providing independent measurement information. This segmentation allows the system to distinguish between proximity effects and material properties without requiring complex multi-frequency excitation circuits.
Solution Approach 2:
Instead of using frequency dimension (multi-frequency excitation) to separate proximity and material property effects, the invention transitions to spatial wavelength dimension by using sensing elements with different spatial wavelengths at a single frequency, achieving the same discrimination capability.
2Measurement precision
If multi-frequency techniques are used for dispersive materials, then more information can be obtained, but phase shifts are small or not measurable making property estimation difficult
Solution Approach 1:
The invention changes the measurement parameter from phase shift (which is small and difficult to measure for dispersive materials) to impedance magnitude, which provides sufficient contrast for accurate material property estimation without requiring precise phase measurement.
3Loss of information
If segmented field sensors with multiple spatial wavelengths are used, then independent measurement of proximity and material properties is enabled, but the device structure becomes more complex
Solution Approach 1:
The sensor comprises multiple sensing elements with different spatial wavelengths, each providing independent measurement information. This segmentation enables simultaneous acquisition of proximity and material property information without requiring complex signal processing or multiple excitation frequencies.
4Adaptability or versatility
If conventional eddy-current testing is used for additive manufacturing materials, then standard procedures can be applied, but characterization of frequency-dispersive materials is limited
Solution Approach 1:
The invention uses impedance magnitude measurements instead of traditional phase-based measurements, which are more suitable for frequency-dispersive materials like additive manufacturing powders and coatings, enabling accurate characterization of effective permeability and other material properties.
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 provides practical characterization of materials by obtaining independent information about proximity and material properties, even for frequency-dispersive materials, improving the accuracy of material assessment in additive manufacturing processes and other applications.
Implementation Method 1
Conventional eddy-current sensing involves the excitation of a conductive drive (primary) winding with an electric current source of prescribed frequency. This produces a time-varying magnetic field
Implementation Method 2
This produces a time-varying magnetic field, which in turn is detected with a sensing (secondary) winding. The spatial distribution of the magnetic field and the field measured by the secondary is influenced by the proximity and physical properties (electrical conductivity and magnetic permeability) of nearby materials
Data Source
AI summary
Disclosed are method and apparatus for measuring material properties. Segmented field sensors have multiple sensing elements at different spatial geometries to capture field components having substantially different depths of penetration. These sensors are excited and measured on these different sensing elements to facilitate characterization of unknown material properties. This is illustrated in some embodiments using eddy current sensors to characterize materials that are frequency dispersive and/or do not produce a measurable phase shifts. Only a single scalar quantity may provide independent information from one or more of the sensing elements. Property estimation techniques, such as those using precomputed databases of sensor responses are used to estimate the unknown material properties.