Eddy Current Probe With Segmented Core Legs
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Solution Overview
Problem
Existing Eddy current probes face challenges in minimizing magnetic footprint while maintaining high signal-to-noise ratio (SNR) and maximum supported lift-off, often compromising on sensitivity due to large magnetic footprints and susceptibility to external noise.
Innovation Solution
The design incorporates a high magnetic permeability body spaced apart from core legs with a gap, allowing for reduced magnetic footprint and improved SNR by altering the distribution of magnetic field lines and incorporating multiple sensing coils to minimize external noise sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the leg spacing is enlarged to increase the maximum supported lift-off, then the maximum supported lift-off is improved, but the magnetic footprint increases
Solution Approach 1:
The U-shaped coil core is divided into two separate legs that are spaced apart, with a high magnetic permeability body positioned between them but not in direct contact. This segmentation allows the magnetic field to be confined more effectively between the legs while maintaining the ability to support greater lift-off distances, thereby reducing the overall magnetic footprint compared to a solid yoke design.
Solution Approach 2:
A high magnetic permeability body is introduced as an intermediary element positioned between the two legs. This body acts as a magnetic shield that confines the magnetic field lines between the legs and prevents them from spreading outwards, thus reducing the magnetic footprint while allowing the legs to be spaced apart for increased lift-off support.
2Measurement precision
If a U-shaped coil core with high magnetic permeability is used to generate strong magnetic field, then the signal-to-noise ratio is improved, but the probe becomes more sensitive to external magnetic noise
Solution Approach 1:
The continuous yoke structure is extracted and replaced with two separate legs spaced apart. This extraction removes the pathway that would otherwise conduct external magnetic noise into the probe, while the high magnetic permeability body positioned between the legs provides magnetic shielding without creating a continuous conductive path for external interference.
Solution Approach 2:
The gap between the legs, which could potentially be seen as a weakness, is converted into a beneficial feature by positioning the high magnetic permeability body within this gap. This configuration uses the gap to isolate the magnetic circuit from external noise sources while maintaining the high magnetic permeability needed for strong field generation and high signal-to-noise ratio.
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 effectively reduces the probe's magnetic footprint and enhances SNR without sacrificing maximum supported lift-off, while also reducing sensitivity to external noise, improving defect detection accuracy.
Implementation Method 1
Probes used for these EC methods typically include an excitation coil, which is used to induce a time-variable magnetic field in a conductive object under test and generate the Eddy currents
Implementation Method 2
The magnetic reluctance of the U-shaped coil core is minimized to improve the amplitude of the generated magnetic field. Hence, the U-shaped coil core is usually be made of a single piece of magnetic permeable material
Implementation Method 3
Magnetic sensing devices such as coils, Hall effect detectors, giant magneto resistor (GMR) or the like are then used to measure the response magnetic field, emitted as a result of the Eddy currents
Data Source
AI summary
There is described an Eddy current probe for non-destructive testing, comprising: a first leg extending along a first longitudinal axis between a first proximal end and a first distal end; a second leg extending along a second longitudinal axis between a second proximal end and a second distal end; a high magnetic permeability body extending at least partially between the first and second longitudinal axes, the high magnetic permeability body being spaced apart from the first and second legs by a gap and the high magnetic permeability body and the first and second legs being each made of a high magnetic permeability material; and at least one excitation coil each secured to at least one of the first leg and the second leg.