scholarly journals Two Novel Information Entropy Indices for Analysis of the Eddy Current Distribution

Entropy ◽  
2018 ◽  
Vol 20 (9) ◽  
pp. 699 ◽  
Author(s):  
Guolong Chen
Keyword(s):  
Current Distribution ◽  
Eddy Current ◽  
Radial Direction ◽  
Current Sensor ◽  
Koch Curve ◽  
Intersection Angle ◽  
Current Distributions ◽  
Exciting Frequency ◽  
Exciting Coil ◽  
Lift Off

The Koch curve exciting coil eddy current sensor is a kind of novel flexible planar eddy current probe. In this study, an intersection angle spectrum entropy index and a radial direction energy spectrum entropy were proposed to evaluate the eddy current distribution. Eddy current distributions induced by one turn of a circular coil and one turn of a second order Koch curve coil feed with different exciting frequency alternative currents and at different lift-off distances, were simulated and the eddy current distributions varying with lift-off distance in different exciting frequencies were compared by the two proposed indices. With the increase of the lift-off distance or the decrease of exciting frequency, the similarity between the shape of the Koch curve and the eddy current distribution became weakened and the degree of the concentration of the eddy current distribution in the specimen under the exciting coil was loosened.

scholarly journals Quantitative evaluation of eddy current distribution by relative entropy and cross entropy

2021 ◽  
pp. 002029402098420
Author(s):  
Guolong Chen ◽  
Zheng Cao
Keyword(s):  
Relative Entropy ◽  
Eddy Current ◽  
Cross Entropy ◽  
Koch Curve ◽  
Intersection Angle ◽  
Current Distributions ◽  
Exciting Frequency ◽  
Small Domain ◽  
Exciting Coil ◽  
Lift Off

Koch curve exciting coil of an eddy current probe can adjust the eddy current distributing in more directions at a small domain to enhance the sensitivity of eddy current probe for short defect detection. In this study, a relative entropy and a cross entropy of tangential intersection angle spectrum are proposed to evaluate the eddy current distributions in the different directions when the eddy current probe is positioned at different lift-off distances and excited by different exciting frequency alternative currents. The eddy current distributions induced by a circular and a fractal Koch curve exciting coils are analyzed by the two entropy indices. With the increasing of the lift-off distance or the decreasing of the exciting frequency, the eddy current distributions induced by the Koch curve exciting coil are close to those induced by the circular exciting coil.

Study on extraction of electrical runout in eddy current measurement using finite element method

2013 ◽  
Vol 228 (6) ◽  
pp. 1077-1086 ◽  
Author(s):  
Xiaolong Chen ◽  
Yanlong Cao ◽  
Zaiyu Lin ◽  
Jiangxin Yang ◽  
Xiaoqi Hu
Keyword(s):  
Finite Element ◽  
Relative Permeability ◽  
Imaginary Part ◽  
Eddy Current ◽  
Material Properties ◽  
Ferromagnetic Material ◽  
Current Sensor ◽  
The Real ◽  
Eddy Current Sensor ◽  
Lift Off

Electrical runout is a bottleneck problem of eddy current sensor, which is caused by the maldistribution/variation of material electromagnetic properties of measurement target. However, extraction methods of electrical runout in eddy current displacement measurement remain ambiguous. Here, a 2D finite element model for the influence analysis of conductivity and permeability of ferromagnetic material on coil impedance of eddy current sensor is reported, which will be beneficial for detecting material properties and guiding manufacturing process. The relationships between the real and imaginary part of coil impedance with the varied material conductivity, relative permeability and the lift-off, which indicates the detecting distance, are investigated. When the conductivity, relative permeability of ferromagnetic material and the lift-off vary within a certain range, the relationships between the real and imaginary part of coil impedance are all nearly linear. This paper further shows that the character of distribution of resistance and reactance in diagram under different material properties and same measuring distance is linear. Furthermore, these lines under different measuring distances are parallel. Also the character under different measuring distances and same material property is linear, but these lines under different material properties are diffuse with same intercept. Altogether, the study shows that this method based on redesign of signal processing and its circuit is feasible and instructive in separating electrical runout from the output of eddy current sensor.

scholarly journals Measurement of Radius of a Metallic Ball Using Eddy Current Testing Based on Peak Frequency Difference Feature

2021 ◽  
Author(s):  
Gang Hu ◽  
Ruochen Huang ◽  
Mingyang Lu ◽  
Lei Zhou ◽  
Wuliang Yin
Keyword(s):  
Eddy Current ◽  
Test Piece ◽  
Peak Frequency ◽  
Frequency Difference ◽  
Current Sensor ◽  
Current Testing ◽  
Lift Off ◽  
Analytical Result ◽  
Current Feature ◽  
Frequency Feature

This paper proposes a linear eddy-current feature to determine the radius of a metallic ball in a non-contact manner. An electromagnetic eddy-current sensor with two coils is placed co-axially to the metal ball during measurement. It is well known that the distance between the sensor and test piece (i.e. lift-off) affects eddy-current signals. In this paper, it is found that the peak frequency feature of inductance spectrum is linear to the lift-off spacing between the centre of coil and ball. Besides, the slope of peak frequencies versus lift-offs is linked to the radius of ball. The radius of metallic balls is retrieved from the experimental and embedded analytical result of the slope. Measurements have been carried out on 6 metallic balls with different radii. The radius of the metallic ball can be retrieved with an error of less than 2 %.

scholarly journals Lift-off tolerant pancake eddy-current sensor for the thickness and spacing measurement of non- magnetic plates

2020 ◽  
Author(s):  
Mingyang Lu ◽  
Xiaobai Meng ◽  
Ruochen Huang ◽  
Liming Chen ◽  
anthony peyton ◽  
...  
Keyword(s):  
Eddy Current ◽  
Test Piece ◽  
Triple Helix ◽  
Outer Radius ◽  
Small Error ◽  
Current Sensor ◽  
Magnetic Vector Potential ◽  
Eddy Current Sensor ◽  
Spacing Distance ◽  
Lift Off

<p>The lift-off spacing distance between the eddy current sensor and test piece will influence the detected signals and accuracy of the measurement. <a>Various techniques including novel sensor designs, features (lift-off point of intersection, lift-off invariance phenomenon), and algorithms have been proposed for the compensation of error caused by the lift-off effect using the eddy current sensor. However, few of these have directly measured the lift-off spacing distance, particularly for the distance up to 15 mm. </a>In this paper, a lift-off tolerant pancake sensor has been designed. By analysing the sensitive region of the magnetic vector potential change (due to the test piece), the receiver of the sensor is designed as a circular spiral pancake coil with a large mean radius and span length (the difference between inner and outer radius). Experiments on the inductance measurement of three different non-magnetic samples have been carried out using both the designed pancake sensor and the previous triple-helix sensor. From the experiment result, the detected signal of the designed sensor has been proved much larger than that of the triple-helix sensor. Besides, simplified algorithms have been proposed for the measurement of the lift-off spacing and thickness of non-magnetic samples when using the proposed pancake sensor. Results show that the lift-off spacing and thickness can be measured with a small error of 0.14 mm (absolute error under 209.66 kHz), and 1.35 % (relative error, under low working frequencies of 142, 238, and 338 Hz) for the lift-off spacing from 1 to 15 mm.</p>

scholarly journals Model of Magnetically Shielded Ferrite-Cored Eddy Current Sensor

Sensors ◽  
2022 ◽  
Vol 22 (1) ◽  
pp. 326
Author(s):  
Darko Vasić ◽  
Ivan Rep ◽  
Dorijan Špikić ◽  
Matija Kekelj
Keyword(s):  
Eddy Current ◽  
Impedance Measurement ◽  
Magnetic Potential ◽  
Current Sensor ◽  
Ferrite Core ◽  
Resistance Change ◽  
Eddy Current Sensor ◽  
Transmitter Coil ◽  
Electromagnetic Models ◽  
Lift Off

Computationally fast electromagnetic models of eddy current sensors are required in model-based measurements, machine interpretation approaches or in the sensor design phase. If a sensor geometry allows it, the analytical approach to the modeling has significant advantages in comparison to numerical methods, most notably less demanding implementation and faster computation. In this paper, we studied an eddy current sensor consisting of a transmitter coil with a finitely long I ferrite core, which was screened with a finitely thick magnetic shield. The sensor was placed above a conductive and magnetic half-layer. We used vector magnetic potential formulation of the problem with a truncated region eigenfunction expansion, and obtained expressions for the transmitter coil impedance and magnetic potential in all subdomains. The modeling results are in excellent agreement with the results using the finite element method. The model was also compared with the impedance measurement in the frequency range from 5 kHz to 100 kHz and the agreement is within 3% for the resistance change due to the presence of the half-layer and 1% for the inductance change. The presented model can be used for measurement of properties of metallic objects, sensor lift-off or nonconductive coating thickness.

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