Eddy Current Probe Identification and Analysis

Tondo, Felipe A.; Porto, Rodrigo Wolff; Villalobos, Luiz Frederico S. S. M.; Brusamarello, Valner; Campestrini, Lucíola

doi:10.1109/tim.2017.2684858

Cited by 20 publications

(7 citation statements)

References 30 publications

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“…From the impedance

, we calculate the inductance

and substitute

with the time constant

[ 9 , 11 ]. The inductance of the sensor

can be described by the sensor model

where

describes the inductance of the air coil (in the absence of the target) that takes temperature drifts into account.…”

Section: Analysis Of An Eddy Current Displacement Sensormentioning

confidence: 99%

See 1 more Smart Citation

Eddy Current Position Measurement in Harsh Environments: A Temperature Compensation and Calibration Approach

Gruber,

Schweighofer,

Berger

et al. 2024

Sensors

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Eddy current displacement sensors (ECDSs) are widely used for the noncontact position measurement of small displacements (lift-offs). Challenges arise with larger displacements as the sensitivity of the ECDSs decreases. This leads to a more pronounced impact of temperature variations on the inductance and, consequently, an increased position error. Design solutions often rely on multiple coils, suitable coil carrier materials, and compensation measures to address the challenges. This study presents a single-coil ECDS for large displacement ranges in environments with high temperatures and temperature variations. The analysis is based on a sensor model derived from an equivalent circuit model (ECM). We propose design measures for both the sensing coil and the target, focusing on material selection to handle the impact of temperature variations. A key part of improving performance under varying temperatures includes model-based temperature compensation for the inductance of the sensing coil. We introduce a method to calibrate the sensor for large displacements, using a modified coupling coefficient based on field simulation data. Our analysis shows that this single-coil ECDS design maintains a position error of less than 0.2% full-scale for a temperature variation of 100K for the sensing coil and 110K for the target.

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“…From the impedance

, we calculate the inductance

and substitute

with the time constant

[ 9 , 11 ]. The inductance of the sensor

can be described by the sensor model

where

describes the inductance of the air coil (in the absence of the target) that takes temperature drifts into account.…”

Section: Analysis Of An Eddy Current Displacement Sensormentioning

confidence: 99%

“…Figure 1 depicts a typical ECDS, comprising a sensing coil and a target. The displacement x between the sensing coil and the target is determined from changes in the impedance

, particularly the change in inductance

[ 8 , 9 , 10 , 11 , 12 ].…”

Section: Introductionmentioning

confidence: 99%

Eddy Current Position Measurement in Harsh Environments: A Temperature Compensation and Calibration Approach

Gruber,

Schweighofer,

Berger

et al. 2024

Sensors

View full text Add to dashboard Cite

show abstract

“…According to the previous reports, the adequate frequency to produce an eddy current for surface crack detection in a steel material is between 1 and 2 MHz, based on penetration depth d expression. 5,6 Moreover, the induction coil used to detect the eddy current in the probe is also hard to be compacted since its sensitivity depends on its geometrical factors. Since the coil is sensitive at high frequency, it requires a high number of conductive windings to detect a magnetic field, which can lead to an increase in the probe size.…”

Section: Introductionmentioning

confidence: 99%

Anisotropy magnetoresistance differential probe for characterization of sub-millimeter surface defects on galvanized steel plate

Nadzri

Saari

Zaini

et al. 2021

Measurement and Control

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Defects such as cracks can cause dangerous damage to the metal structure and may lead to structural collapses. Cracks can exist in various shapes and sizes where they can start to develop from small scale lower than 1 mm and spread to contribute to the complete fracture of components. Hence, early discovery and monitoring of any cracks in their early stage are crucial to prevent any sudden fatal accidents in the future. This work presents the study and detailed analysis of an ECT probe’s development based on AMR sensors to identify sub-millimeter surface cracks in galvanized steel plates. The probe consists of an excitation coil that induces an eddy current in sample plates and two AMR sensors that detect the differential eddy current-induced magnetic response. A phase-sensitive detection technique with a lock-in amplifier is used to evaluate the magnetic field distribution detected by the AMR sensors. The measured magnetic responses are classified to the depth, width, length, and complex shapes of artificial slits, and the probe is used to perform line scans and 2-D map scans above the slits’ positions. The probe was able to characterize slits with a depth and width as low as 210 and 50 µm, respectively, by using an excitation current of 4 mA at 1 kHz. The slit orientations that were perpendicular to the differential direction of the AMR sensors were clearly visualized, with their estimated lengths showed a good correlation with the physical slit lengths. In the future, the developed system can be expected to help towards the development of a more sophisticated crack detection system where real-time inspections can be realized and applied in various fields.

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“…Hence, transfer function as well as system identification were also used to characterize the PECT system. Tondo et al 17 deduced the transfer function representing the admittance of the probe coil from the equivalent circuit. Then an inductive time constant was obtained from the transfer function parameters and explored as a new feature to assess the size of slots fabricated on a metal sample.…”

Section: Introductionmentioning

confidence: 99%

Parameter identification of pulsed eddy current testing equivalent circuit model and its application to defect evaluation

Fan

Song

2021

Measurement and Control

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The equivalent circuit model of pulsed eddy current testing (PECT) has simple mathematics but its applications are limited to qualitative analysis such as principle illustration and signal interpretation. In this paper, the parameters of equivalent circuit model are estimated using system identification method and quantitative relationships are found between some of the parameters and the size of the defect. The equivalent circuit equations were solved from the perspective of system analysis to yield the system transfer function. An m-sequence of 10 order was selected to excite the system and the probe current was used as the output. A set of experiment input-output data for system identification were obtained by performing experiments on two aluminium alloy 6061 slabs, one of which was machined with five slots of different widths, and the other one was machined with five depth-varied slots. The equivalent circuit parameters were finally estimated based on the identified transfer function parameters. It is found that the values of resistance and self-inductance of the secondary windings decrease greatly and monotonically with the increase of the slot width or depth. The self-inductance is more sensitive to the slot size variation than the resistance. Both of them have the potential to serve as the signal feature for defect evaluation in PECT applications.

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Eddy Current Probe Identification and Analysis

Cited by 20 publications

References 30 publications

Eddy Current Position Measurement in Harsh Environments: A Temperature Compensation and Calibration Approach

Eddy Current Position Measurement in Harsh Environments: A Temperature Compensation and Calibration Approach

Anisotropy magnetoresistance differential probe for characterization of sub-millimeter surface defects on galvanized steel plate

Parameter identification of pulsed eddy current testing equivalent circuit model and its application to defect evaluation

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