Eddy Current Inspection Using Coded Spread Spectrum
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Solution Overview
Problem
Eddy current inspection methods face challenges in accurately interpreting impedance plane signals, requiring specialized training and being time-consuming, especially in noisy environments and when detecting defects larger than the probe diameter or at varying depths within materials.
Innovation Solution
The method employs a static array of sensors using low cross-correlation spread spectrum signals, allowing for simultaneous operation across a wide frequency range without interference, and compensates for lift-off and temperature variations, enabling accurate direct amplitude and phase measurement through coded spread spectrum and correlation, which improves signal-to-noise ratio and allows for volumetric visualization of material properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional eddy current inspection methods are used, then material defects can be detected, but the inspection process is time-consuming and requires special operator training due to difficult impedance plane signal interpretation
Solution Approach 1:
The patent transforms the complex impedance plane signal parameters into simpler amplitude and phase parameters through signal processing. By changing the parameter representation from impedance plane (which requires specialized interpretation) to amplitude/phase (which are more intuitive), the system maintains defect detection accuracy while reducing inspection time and operator training requirements.
Solution Approach 2:
The patent introduces an intermediary signal processing stage that converts the raw impedance plane signals into amplitude and phase information. This intermediary transformation acts as a bridge between the complex electromagnetic signals and the interpretable defect information, eliminating the need for operators to directly interpret difficult impedance plane patterns.
2Area of stationary object
If multiple coils are excited simultaneously at the same frequency, then inspection coverage is increased, but coupling among different channels occurs
Solution Approach 1:
The patent employs periodic modulation of the excitation signals using orthogonal functions (such as sine and cosine waves at different phases). This periodic action with orthogonal characteristics allows multiple coils to operate simultaneously at the same frequency without coupling, as the orthogonal signals can be independently separated and processed, maintaining both inspection coverage and signal independence.
Solution Approach 2:
The patent creates a composite signal structure by combining multiple orthogonal modulation functions. This composite signaling approach allows simultaneous excitation of multiple coils while maintaining mathematical independence between channels, effectively preventing coupling while maximizing inspection coverage.
3Measurement precision
If spread spectrum signals are used in noisy environments, then signal-to-noise ratio is improved, but signal complexity increases
Solution Approach 1:
The patent replaces complex mechanical signal processing with mathematical correlation operations. By using correlation of the received signal with the known transmitted spread spectrum signal, the system achieves noise rejection and signal-to-noise ratio improvement through computational methods rather than complex hardware filtering, reducing device complexity while maintaining measurement precision.
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 enables precise detection of defects and material properties, including structural integrity, without the need for physical scanning, improving inspection efficiency and accuracy in noisy environments and providing feedback for manufacturing processes.
Implementation Method 1
Eddy currents are created through a process called electromagnetic induction. When alternating current is applied to the conductor, such as copper wire, a magnetic field develops in and around the conductor.
Implementation Method 2
Eddy currents are induced electrical currents that flow in a circular path.
Data Source
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AI summary
A method of inspecting a material comprising: producing at least one eddy current excitation in a material under test; sensing said at least one eddy current excitation in the material under test; wherein the method comprises using a low cross-correlation coded spread spectrum to produce said at least one eddy current excitation, and using a correlation technique to make a determination of amplitude and phase of the sensed eddy current excitation; wherein the method further comprises using the determination to make an assessment of the material under test.