Thickness Measurement of Metallic Film Based on a High-Frequency Feature of Triple-Coil Electromagnetic Eddy Current Sensor

Lü, Mingyang; Chen, Liming; Meng, Xiaobai; Huang, Ruochen; Peyton, A. J.; Yin, Wuliang

doi:10.1109/tim.2020.3027929

Cited by 27 publications

(16 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…From (33) to (35), Z s and Z a denote the measured impedance with and without (in the free space) the sample, respectively; L s and L a are the experimental inductance with and without (in the free space) the sample, respectively; and R s and R c are the mutual resistance (real part of the impedance) caused by the sample and coils, respectively. By using the inductance change equation in (35) (which is corresponding to the analytical equations in 1 and 2), the ambient noise signals (including the mutual resistance R s and R c or potentially high-frequency parasitic impedance of the coils Z c [35]) are excluded from the experimental inductance change. Besides, the working frequency of the impedance analyzer is from 1 kHz to 5 MHz, which is much lower than the resonance frequency.…”

Section: Table II Parameters Of Magnetic Steelsmentioning

confidence: 99%

Inversion of Distance and Magnetic Permeability Based on Material-Independent and Liftoff Insensitive Algorithms Using Eddy Current Sensor

Lü

Meng

Huang

et al. 2021

IEEE Trans. Instrum. Meas.

Self Cite

View full text Add to dashboard Cite

Eddy current sensors can be used to test the characteristics and measure the parameters of the conductive samples. As the main obstacle of the multifrequency eddy current (MEC) sensor, the liftoff distance affects the effectiveness and accuracy of the measurement. In this article, a material-independent algorithm has been proposed for the restoration of the liftoff distance when using the MEC sensor, which is based on the approximation under the thin-skin effect. Experiment testing on the performance of the proposed method is presented. The results show that from the dual-frequency inductance, the liftoff distance could be restored with a maximum error of 0.24 mm for the distance up to 12 mm. Besides, the derived liftoff distance is used for the inversion of the magnetic permeability. Based on a liftoff insensitive inductance (LII) feature, the magnetic permeability of steels can be inversed in an iterative manner, with an error of less than 0.6 % for the liftoff distance up to 12 mm.

show abstract

Section: Table II Parameters Of Magnetic Steelsmentioning

confidence: 99%

Inversion of Distance and Magnetic Permeability Based on Material-Independent and Liftoff Insensitive Algorithms Using Eddy Current Sensor

Lü

Meng

Huang

et al. 2021

IEEE Trans. Instrum. Meas.

Self Cite

View full text Add to dashboard Cite

show abstract

“…The thickness of both the aluminium film (with different actual thickness) and copper film (with different radii) can be reconstructed by inputting the measured electrical resistance into (34) and (35). As shown in Fig.…”

Section: B Reconstructed Thickness For Different Working Frequenciesmentioning

confidence: 99%

“…K is a coil factor and defined in (3). α is related to the wavenumber of incident transverse electric (TE) planar electromagnetic wave [33][34][35][36][37][38][39][40][41][42][43]. P(α) is the integration of Bessel terms defined in (10).…”

Section: Introductionmentioning

confidence: 99%

Thickness Measurement of Circular Metallic Film Using Single-Frequency Eddy Current Sensor

Lü¹,

Meng²,

Huang³

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

In many advanced industrial applications, the thickness is a critical index, especially for metallic coatings. However, the variance of lift-off spacing between sensors and test pieces affects the measured voltage or impedance, which leads to unreliable results from the sensor. Massive research works have been proposed to address the lift-off issue, but few of them applies to the thickness measurement of planar metallic films with finite-size circular (disk) geometry. Previously, a peak-frequency feature from the swept-frequency inductance was used to compensate the measurement error caused by lift-offs, which was based on the slow-changing rate of impedance phase term in the Dodd-Deeds formulas. However, the phase of measured impedance is nearly invariant merely on a limited range of sample thicknesses and working frequencies. Besides, the frequency sweeping is time-consuming, where a recalibration is needed for different sensor setups applied to the online real-time measurement. In this paper, a single-frequency algorithm has been proposed, which is embedded in the measurement instrument for the online real-time retrieval of thickness. Owing to the single-frequency measurement strategy, the proposed method does not need to recalibrate for different sensor setups. The thickness retrieval is based on a triple-coil sensor (with one transmitter and two receivers). The thickness of metallic disk foils is retrieved from the measured electrical resistance of two transmitter-receiver sensing pairs. Experiments on materials of different electrical conductivities (from direct current), thicknesses and planar sizes (radii) have been carried out to verify the proposed method. The error for the thickness retrieval of conductive disk foils is controlled within 5 % for lift-offs up to 5 mm.

show abstract

“…In our previous work, strategies including algorithms of the peak frequency and different sensor designs have been proposed for eliminating the lift-off effect on the property measurement of plates [20][21][22][23][24][25][26][27][28][29][30][31][32][33], which have been found to efficiently compensate for the error caused by a small lift-off spacing. However, these proposed methods cannot be applied for an extended lift-off range (e.g.…”

Section: Introductionmentioning

confidence: 99%

Liftoff Tolerant Pancake Eddy-Current Sensor for the Thickness and Spacing Measurement of Nonmagnetic Plates

Lü

Meng

Huang

et al. 2021

IEEE Trans. Instrum. Meas.

Self Cite

View full text Add to dashboard Cite

The lift-off spacing distance between the eddy current sensor and test piece will influence the detected signals and accuracy of the measurement. 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. 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.

show abstract

Thickness Measurement of Metallic Film Based on a High-Frequency Feature of Triple-Coil Electromagnetic Eddy Current Sensor

Cited by 27 publications

References 32 publications

Inversion of Distance and Magnetic Permeability Based on Material-Independent and Liftoff Insensitive Algorithms Using Eddy Current Sensor

Inversion of Distance and Magnetic Permeability Based on Material-Independent and Liftoff Insensitive Algorithms Using Eddy Current Sensor

Thickness Measurement of Circular Metallic Film Using Single-Frequency Eddy Current Sensor

Liftoff Tolerant Pancake Eddy-Current Sensor for the Thickness and Spacing Measurement of Nonmagnetic Plates

Contact Info

Product

Resources

About