Van-Dong Doan

Da Nang University of Technology

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Jen-Tzong Jeng

National Kaohsiung University of Science and Technology

Huu-Thang Nguyen

Thai Nguyen University

Duy-Vinh Dao

Nong Lam University Ho Chi Minh City

Chinh-Hieu Dinh

National Kaohsiung University of Science and Technology

Thi-Trang Pham

National Kaohsiung University of Science and Technology

Long-Vu Bui

National Kaohsiung University of Science and Technology

Truong-Han Nguyen

National Kaohsiung University of Science and Technology

Bo-Yao Liang

National Kaohsiung University of Science and Technology

Guan-Wei Huang

National Kaohsiung University of Science and Technology

Xuan Thang Trinh

Hung Yen University of Technology and Education

Cooperative Institutions

National Kaohsiung University of Science and Technology

Industrial Technology Research Institute

National University of Kaohsiung

National Kaohsiung University of Applied Sciences

National Taiwan University

Nong Lam University Ho Chi Minh City

Thai Nguyen University

Hồng Đức University

Hung Yen University of Technology and Education

University of Transport and Communications

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Detection of Surface and Subsurface Flaws with Miniature GMR-Based Gradiometer

Sensors (2022)

Huu-Thang Nguyen Jen-Tzong Jeng Van-Dong Doan Chinh-Hieu Dinh Xuan Thang Trinh

The eddy-current (EC) testing method is frequently utilized in the nondestructive inspection of conductive materials. To detect the minor and complex-shaped defects on the surface and in the underlying layers of a metallic sample, a miniature eddy-current probe with high sensitivity is preferred for enhancing the signal quality and spatial resolution of the obtained eddy-current images. In this work, we propose a novel design of a miniature eddy-current probe using a giant magnetoresistance (GMR) sensor fabricated on a silicon chip. The in-house-made GMR sensor comprises two cascaded spin-valve elements in parallel with an external variable resistor to form a Wheatstone bridge. The two elements on the chip are excited by the alternating magnetic field generated by a tiny coil aligned to the position that balances the background output of the bridge sensor. In this way, the two GMR elements behave effectively as an axial gradiometer with the bottom element sensitive to the surface and near-surface defects on a conductive specimen. The performance of the EC probe is verified by the numerical simulation and the corresponding experiments with machined defects on metallic samples. With this design, the geometric characteristics of the defects are clearly visualized with a spatial resolution of about 1 mm. The results demonstrate the feasibility and superiority of the proposed miniature GMR EC probe for characterizing the small and complex-shaped defects in multilayer conductive samples.

Wheatstone bridge

10.3390/s22083097

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Citations (1)

Classification of steel balls by resonant eddy-current sensor

Measurement Science and Technology (2021)

Duy-Vinh Dao Jen-Tzong Jeng Van-Dong Doan Chinh-Hieu Dinh Thi-Trang Pham

Abstract Objective: The quality and work-life of ball bearings depend on the material properties of the steel ball, hence it is necessary to carefully classify their properties for bearings and related applications. This paper presents the classification of steel balls based on the subtle differences in their electromagnetic properties. Approach: The conductivity and magnetic susceptibility for steel balls of the same kind are measured to investigate their correlation with eddy-current (EC) signals. Main results: The developed EC sensor works at the resonant frequency of 117 kHz with an optimal readout resistance of 15 kΩ, which helps to boost the signal level without a high-gain preamplifier. To detect the EC signal, the steel ball under test moves through the pickup coil, and the recorded data are used to build a voltage probability map (VPM) for the classification of the steel ball properties. Experimental results show that the steel balls with and without the hardening process can be identified by the change in the amplitude and phase of the EC signal, which is consistent with the observed change in the electromagnetic properties of steel balls. Significance: The built system can be applied to the related industries to check the quality of steel balls before use.

Electrical steel

Ball (mathematics)

SIGNAL (programming language)

Hardening (computing)

10.1088/1361-6501/ac32ed

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Citations (4)

Real-Time Thickness Measurement Using Resonant Eddy-Current Sensor

IEEE Transactions on Instrumentation and Measurement (2021)

Chinh-Hieu Dinh Jen-Tzong Jeng Guan-Wei Huang Jingyuan Chen Yi-Shian Chiang

In this work, we propose a real-time noncontact thickness measurement system for conductive materials based on an inductor-capacitor (LC) resonant eddy-current sensor. For the aluminum, copper, stainless steel 304, and carbon steel samples of various thicknesses, the in-phase and quadrature components of the sensor output taken during liftoff scans are found to be a series of quadratic-like curves on the phase versus logarithmic amplitude diagram. These curves can be used to generate the standard phase-amplitude relations for thickness conversion. The phase-amplitude relations of the thickness between the values of standard samples are calculated by cubic spline interpolation. With the standard database of phase-amplitude relations, the noncontact thickness measurement was implemented in real time for the copper foil sample with an error of ±3% when the liftoff distance is less than 5 mm. The liftoff tolerance is as large as 100% of the probe diameter, indicating that the proposed method is useful for online quality inspection of conductor films on flexible substrates.

Eddy-current sensor

Quadrature (astronomy)

10.1109/tim.2021.3077997

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Citations (11)

High-Resolution Flaw Detection using Eddy-Current Probe Array Based on Giant Magnetoresistance Sensors

Long-Vu Bui Jen-Tzong Jeng Hua‐Chih Huang Huu-Thang Nguyen Van-Dong Doan

10.1109/intermagshortpapers61879.2024.10576750

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Islanding and Detection of Distributed Generation Islanding using Negative Sequence Component of Current

International Journal of Engineering Research and (2017)

Van-Dong Doan

Islanding

Component (thermodynamics)

Sequence (biology)

Source

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Liftoff-Insensitive Conductivity Mapping Using a Self-Resonant Eddy-Current Probe

IEEE Transactions on Instrumentation and Measurement (2023)

Long-Vu Bui Jen-Tzong Jeng Duy-Vinh Dao Van-Dong Doan Huu-Thang Nguyen

This study proposes a novel approach for contactless conductivity measurement of nonmagnetic metal sheets for a production line. The system uses a self-resonant eddy-current sensor as the conductivity probe, of which the sensitivity is enhanced by minimizing the parasitic resistance in the resonant circuit. The output responses at various liftoff distances are nonlinear curves unique to the sample’s conductivity. The quaternary polynomial regression is utilized to establish the analytic approximation function to depict the correlation between the phase and the logarithmic magnitude for standard samples. The phase-magnitude relationships are generally monotonic and useful for conductivity conversion using the standard data. The polynomial interpolation is employed to establish the phase-conductivity relations based on the standard samples. The self-developed computer software can instantaneously convert the probe output into the conductivity of the metallic material under test. The experimental findings point to the feasibility of the suggested method that can perform conductivity measurement with a relative error of less than 3 % at a liftoff distance of less than 1 mm, indicating the practicability of the proposed technique in conductivity mapping for non-ferrous metals.

Interpolation

10.1109/tim.2023.3338674

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High-Resolution Flaw Detection Using Eddy-Current Probe Array Based on Giant Magnetoresistance Sensors

IEEE Transactions on Magnetics (2024)

Long-Vu Bui Jen-Tzong Jeng Hua‐Chih Huang Huu-Thang Nguyen Van-Dong Doan

This work presents a flaw detection system consisting of an array of eddy-current (EC) probes based on giant-magnetoresistance (GMR) sensors for mapping the defects on a metal sheet. Before measurement, a spatially dependent calibration process was done to compensate for the inter-channel inconsistency in output offsets and responsivity. The calibrated 8-channel probe array exhibits high sensitivity in revealing tiny features of defects with superior spatial resolution. The proposed system allows for the visualization of the geometric characteristics of the surface defects with an inter-spacing of more than 2 mm. The suggested approach has great potential in the nondestructive testing of metallic sheets for the characterization of minor and intricately shaped flaws.

Sensor array

10.1109/tmag.2024.3402331

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Citations (1)

Development of Electromagnetic Acoustic Transducer System for Coin Classification

Sensors (2022)

Duy-Vinh Dao Jen-Tzong Jeng Van-Dong Doan Huu-Thang Nguyen Bo-Yao Liang

In this work, a method for identifying counterfeit coins based on an electromagnetic acoustic transducer (EMAT) to detect the difference in the coin’s natural acoustic frequency response is presented. In the experimental system, the acoustic oscillation induced by a pulsed magnetic field is received by a microphone and recorded by an oscilloscope. The natural acoustic frequency of the coin is resolved by the fast Fourier transform (FFT) method on the computer. It is found that the natural frequencies of the possible counterfeit coins deviate significantly from the standard ranges of 16.9 to 17.4 kHz for the authentic 50 New Taiwan Dollar (NTD) coins. The observed natural frequencies of the coin are consistent with the values predicted by analytical estimation. We also built a prototype EMAT coin classification system to detect the natural acoustic frequency by direct frequency counting using a microcontroller. The prototype system demonstrates that a counterfeit coin can be identified by its natural frequency in less than 30 ms using the EMAT method. The proposed technique can be applied to the vending machine to improve the accuracy in discriminating between authentic and counterfeit coins.

10.3390/s22239055

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Surface and Subsurface Eddy-Current Imaging With GMR Sensor

IEEE Transactions on Instrumentation and Measurement (2021)

Huu-Thang Nguyen Jen-Tzong Jeng Van-Dong Doan Chinh-Hieu Dinh Duy-Vinh Dao

The high sensitivity for low-frequency fields makes the tiny giant magnetoresistance (GMR) sensors suitable for high-resolution eddy-current (EC) imaging. In this work, we proposed a novel design of the miniature differential EC probe with a spin-valve GMR sensor for surface and subsurface EC imaging. The differential EC probe consists of a full-bridge GMR chip mounted vertically on the edge of a tiny printed circuit board to reduce the liftoff distance. The excitation signal is perpendicular to the sensing axis of the GMR chip, which makes it sensitive to the unbalance EC signal on the surface of a conductive sample. The miniature EC probe operated at frequencies from 5 to 65 kHz is sensitive to the hidden defects on a flat conductor. The spatial resolution and stability of the device are verified by taking the 2-D scan images over the copper film samples with hidden defects, showing that the spatial resolution is better than 2 mm for the flaw 0.5 mm below the top surface of a multilayer structure. The proposed device is useful in the detection of small surface and subsurface defects, such as cracks, metal loss, and other mechanical damages.

SIGNAL (programming language)

10.1109/tim.2021.3120378

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Citations (14)

Development of a Broad Bandwidth Helmholtz Coil for Biomagnetic Application

IEEE Transactions on Magnetics (2020)

Van-Dong Doan Jen-Tzong Jeng Tsang-Hao Tsao Thi-Trang Pham Guan-Wei Huang

The alternating uniform magnetic field is useful for the biomagnetic study with magnetic nanoparticles. However, for the coil system driven by the magnetic field generator with a conventional low-voltage power source, it is challenging to achieve the desired field strength with a large coil due to the large impedance at higher frequencies. This article proposed a Helmholtz coil system that can generate the dc and ac magnetic field up to 1.3 kHz with low distortion. In order to overcome the inductive load, a computer-controlled parallel capacitor array was designed and built to tune the series coil-capacitor circuit to the resonant frequency. Experimental results show that the coil system has a bandwidth over 1 kHz with a 1% uniform region covering the 10 × 10 mm sample area. The proposed system is promising for the application in biomagnetic assay using the tunnel magnetoresistance sensors.

Helmholtz coil

Helmholtz free energy

Search coil

Voice coil

10.1109/tmag.2020.3007490

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Citations (8)