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

Previously, various techniques have been proposed for reducing the lift-off effect on the thickness measurement of the non-magnetic films, including the peak-frequency feature and phase feature in the Dodd-Deed analytical formulation. To realise a real-time feedback response on the thickness monitoring, the phase term in the Dodd-Deeds formulation must be taken off the integration. Previous methods were based on the slow change rate of the phase term when compared to the rest of the term – the magnitude term. However, the change rate of the phase term is still considerable for a range of working frequencies. In this paper, a high-frequency feature has been found. That is, the ratio between the imaginary and real part of the phase term is proportional to the integral variable under high frequencies. Based on this proportion relationship, the phase term has been taken out; and a thickness algorithm has been proposed. By combing the measured impedance from the custom-built sensor (three coils), the thickness of the metallic film can be reconstructed. Experiments have been carried out for the verification of the proposed scenario. Results show that the thickness of the metal film can be reconstructed with a small error of less than 2 %, and immune to a reasonable range of lift-offs.

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

IEEE Transactions on Instrumentation and Measurement ◽

10.1109/tim.2020.3027929 ◽

2021 ◽

Vol 70 ◽

pp. 1-8 ◽

Cited By ~ 2

Author(s):

Mingyang Lu ◽

Liming Chen ◽

Xiaobai Meng ◽

Ruochen Huang ◽

Anthony Peyton ◽

...

Keyword(s):

Eddy Current ◽

High Frequency ◽

Thickness Measurement ◽

Metallic Film ◽

Current Sensor ◽

Eddy Current Sensor ◽

Frequency Feature

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

10.20944/preprints202107.0220.v2 ◽

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 %.

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

10.20944/preprints202102.0237.v1 ◽

2021 ◽

Author(s):

Mingyang Lu ◽

Xiaobai Meng ◽

Ruochen Huang ◽

Liming Chen ◽

Anthony Peyton ◽

...

Keyword(s):

Real Time ◽

Finite Size ◽

Critical Index ◽

Measurement Instrument ◽

Circular Disk ◽

Peak Frequency ◽

Thickness Measurement ◽

Industrial Applications ◽

Single Frequency ◽

Lift Off

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.

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A High-Frequency Phase Feature for the Measurement of Magnetic Permeability Using Eddy Current Sensor

10.20944/preprints202108.0154.v1 ◽

2021 ◽

Author(s):

Mingyang Lu ◽

Xiaobai Meng ◽

Ruochen Huang ◽

Liming Chen ◽

Anthony Peyton ◽

...

Keyword(s):

Magnetic Permeability ◽

High Frequency ◽

Impedance Measurement ◽

Destructive Testing ◽

Zero Crossing ◽

Linear Feature ◽

Signal Features ◽

Fast Processing ◽

Lift Off ◽

Phase Term

Electromagnetic sensing has been used for diverse applications of non-destructive testing, including the surface inspection, measurement of properties, object characterization. However, the measurement accuracy could be significantly influenced by the lift-off between sensors and samples. To address the issue caused by lift-offs, various strategies have been proposed for the permeability measurement of ferromagnetic steels, which mainly involves different sensor designs and signal features (e.g., the zero-crossing feature). In this paper, a single high-frequency scenario for the permeability retrieval is introduced. By combining the signal of two sensing pairs, the retrieval of magnetic permeability is less affected by the lift-off of sensors. Unlike the previous strategy on reducing the lift-off effect (directly taking the phase term out of the integration) using the Dodd-Deeds analytical method, the proposed method is based on a high-frequency linear feature of the phase term. Therefore, this method has the merit of high accuracy and fast processing for the permeability retrieval (a simplified version of Dodd-Deeds analytical formulas after the integration). Experimental measurement has been carried out on the impedance measurement of designed sensors interrogating ferromagnetic dual-phase steels. For sensor lift-offs of up to 10 mm, the error of the permeability retrieval is controlled within 4 % under the optimal frequency.

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

10.20944/preprints202107.0220.v1 ◽

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

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Faculty Opinions recommendation of Comparison of residual stromal bed thickness measurement among very high-frequency digital ultrasound, intraoperative handheld ultrasound, and optical coherence tomography.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.13477033.14857144 ◽

2012 ◽

Author(s):

Jason Stahl ◽

Jason Philip Brinton

Keyword(s):

Optical Coherence Tomography ◽

High Frequency ◽

Thickness Measurement ◽

Optical Coherence ◽

Very High Frequency ◽

Handheld Ultrasound ◽

Bed Thickness ◽

Very High

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Evaluation of Coating Thickness Using Lift-Off Insensitivity of Eddy Current Sensor

Sensors ◽

10.3390/s21020419 ◽

2021 ◽

Vol 21 (2) ◽

pp. 419

Author(s):

Xiaobai Meng ◽

Mingyang Lu ◽

Wuliang Yin ◽

Abdeldjalil Bennecer ◽

Katherine J. Kirk

Keyword(s):

Eddy Current ◽

Coating Thickness ◽

Thickness Measurement ◽

Eddy Current Testing ◽

Thickness Variation ◽

Testing Technique ◽

Current Testing ◽

Thin Skin ◽

Embedded Algorithms ◽

Lift Off

Defect detection in ferromagnetic substrates is often hampered by nonmagnetic coating thickness variation when using conventional eddy current testing technique. The lift-off distance between the sample and the sensor is one of the main obstacles for the thickness measurement of nonmagnetic coatings on ferromagnetic substrates when using the eddy current testing technique. Based on the eddy current thin-skin effect and the lift-off insensitive inductance (LII), a simplified iterative algorithm is proposed for reducing the lift-off variation effect using a multifrequency sensor. Compared to the previous techniques on compensating the lift-off error (e.g., the lift-off point of intersection) while retrieving the thickness, the simplified inductance algorithms avoid the computation burden of integration, which are used as embedded algorithms for the online retrieval of lift-offs via each frequency channel. The LII is determined by the dimension and geometry of the sensor, thus eliminating the need for empirical calibration. The method is validated by means of experimental measurements of the inductance of coatings with different materials and thicknesses on ferrous substrates (dual-phase alloy). The error of the calculated coating thickness has been controlled to within 3% for an extended lift-off range of up to 10 mm.

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82 Struggle behavior and vocalizations of male piglets during castration

Journal of Animal Science ◽

10.1093/jas/skaa054.004 ◽

2020 ◽

Vol 98 (Supplement_3) ◽

pp. 3-4

Author(s):

Maria E Lou ◽

Yuzhi Li ◽

Beth Ventura

Keyword(s):

Birth Weight ◽

Acute Pain ◽

High Frequency ◽

Video Recording ◽

Low Frequency ◽

Peak Frequency ◽

Analysis Software ◽

Chi Square ◽

Behavioral Indicators ◽

Treatment Groups

Abstract Castration without the use of analgesia is routinely performed on male piglets. The objective of this study was to assess acute pain during castration through behavioral indicators. Piglets (n=88) were randomly allocated to one of two treatments: castration without the use of analgesia (C) and sham-castration (S). Within 24 hours after birth (birth weight = 1.78kg ±0.71), identical procedures were followed for both treatment groups, except sham piglets were not castrated. Struggle behavior (curl ups, leg kicks, and body flailing) and vocalizations were collected via continuous video recording as piglets received treatment from start (first application of scalpel) to end (application of iodine). Vocalization parameters (duration and peak frequency) were analyzed using the Raven Pro: Interactive Sound Analysis Software (Version 1.5). Peak frequency was defined as low (< 1000 Hz) and high (≥ 1000 Hz). Data were analyzed using the Glimmix Procedure of SAS. For struggle behavior, treatment did not affect curl up frequency. However, castrated piglets kicked more frequently than did sham piglets (C=28.8±0.9 vs. S=21.3±0.9 kicks/min; P=0.02). Additionally, 52% of castrated piglets displayed body flailing, whereas only 4.4% of sham piglets displayed the same behavior (Chi-Square = 24.2; P < 0.0001). For vocalizations, no difference was found for duration and peak frequency of low frequency calls. However, castrated piglets responded with more high frequency calls than sham piglets (C=23.6±0.3 vs. S=18.6±0.3 calls/min; P=0.04). High frequency calls tended to be of longer duration for castrated piglets (C=0.45±0.04 vs. S=0.27±0.04 sec/call; P=0.08). Results indicate that castration without the use of analgesia increased the frequency of leg kicks, body failing, and high frequency calls. This suggests that leg kicks, body flailing, and high frequency calls maybe useful behavioral indicators of acute pain in piglets.

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High Frequency Peakers

Publications of the Astronomical Society of Australia ◽

10.1071/as03005 ◽

2003 ◽

Vol 20 (1) ◽

pp. 79-84 ◽

Cited By ~ 19

Author(s):

Daniele Dallacasa

Keyword(s):

Radio Source ◽

High Frequency ◽

Peak Frequency ◽

Source Size ◽

Host Galaxy ◽

Radio Sources ◽

Inner Region

AbstractThere is quite a clear anticorrelation between the intrinsic peak frequency and the overall radio source size in compact steep spectrum (CSS) and gigahertz peaked spectrum (GPS) radio sources. This feature is interpreted in terms of synchrotron self-absorption (although free–free absorption may play a role as well) of the radiation emitted by a small radio source which is growing within the inner region of the host galaxy. This leads to the hypothesis that these objects are young and that the radio source is still developing/expanding within the host galaxy itself.Very young radio sources must have the peak in their radio spectra occurring above a few tens of gigahertz, and for this reason they are termed high frequency peakers (HFPs). These newly born radio sources must be very rare given that they spend very little time in this stage. Ho = 100 km s−1 Mpc−1 and qo = 0.5 are used throughout this paper.

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