Mutual Impedance of Planar Eddy-Current Driver–pickup Spiral Coils

IEEE Trans. Instrum. Meas.

Yin

Peyton

et al. 2016

Lift-off variation causes errors in the eddy current thickness measurements of metallic plates. In this paper, we have developed an algorithm that can compensate for this variation and produce an index that is linked to the thickness, but is virtually independent of lift-off. This index, termed as the compensated peak frequency, can be obtained from the measured multifrequency inductance spectral data using the algorithm we developed in this paper. This method has been derived through mathematical manipulation and verified by both the simulation and experimental data. Accuracy in the thickness measurements at different lift-offs proved to be within 2%.Index Terms-Eddy current testing, lift-off variation, new compensation algorithm, thickness measurement.

Section: Theoretical Derivation Of Thementioning

confidence: 98%

A Novel Compensation Algorithm for Thickness Measurement Immune to Lift-Off Variations Using Eddy Current Method

IEEE Trans. Instrum. Meas.

Yin

Peyton

et al. 2016

“…1 shows the circular drive-pickup coil windings scanning vertically (along axis) over a long ideal surface slot of a conductive half-space. The analytical mutual impedance change caused by the surface slot is reported in [28], which is based on the eddy-current thin-skin regime proposed by Harfield and Bowler [26]. That is, for the case that the crack length and depth are over 3 to 4 times of the eddy-current skin depth (equation 1), the impedance change due to the surface slot can be well approximated by the following expression.…”

Section: A Original Formulas Of Thin-skin Regime -Mutual-impedance Omentioning

confidence: 99%

Determination of Surface Crack Orientation Based on Thin-Skin Regime Using Triple-Coil Drive-Pickup Eddy-Current Sensor

Meng

Huang

et al. 2020

Preprint

Electromagnetic sensors have been used for inspecting small surface defects of metals. Based on the eddy-current thin-skin regime, a revised algorithm is proposed for a triple-coil drive-pickup eddy-current sensor scanning over long surface crack slots (10 mm) with different rotary angles. The method is validated by the voltage measurement of the designed EC sensor scanning over a benchmark (ferromagnetic) steel with surface defects of different depths and rotary angles. With an additional sensing coil for the designed EC sensor, the defect angle (or orientation) can be measured without spatially and coaxially rotating the excitation coil. By referring to the voltage change (due to the defect) diagram (voltage sum versus voltage different) of two sensing pairs, the rotary angle of the surface crack is retrieved with a maximum residual deviation of 3.5 %.

“…Both analytical [21][22][23] and numerical methods [24,25] have been proposed for the interaction analysis between EC sensors and surface crack slots on metals. For the analytical technique, combining the Harfield-Bowler eddy-current thin-skin model [26] with a two-port system of surface-integral formulas proposed by Auld [27], Burke and Ditchburn have proposed the analytical model of mutual impedance change due to an ideal surface crack [28]. Moreover, Theodoulidis has proposed the revised analytical model for the tilted single-coil sensor above the surface slot [29].…”

Section: Introductionmentioning

confidence: 99%

Determination of Surface Crack Orientation Based on Thin-Skin Regime Using Triple-Coil Drive–Pickup Eddy-Current Sensor

IEEE Trans. Instrum. Meas.

Meng

Huang

et al. 2021

Electromagnetic sensors have been used for inspecting small surface defects of metals. Based on the eddycurrent thin-skin regime, a revised algorithm is proposed for a triple-coil drive-pickup eddy-current sensor scanning over long surface crack slots (10 mm) with different rotary angles. The method is validated by the voltage measurement of the designed EC sensor scanning over a benchmark (ferromagnetic) steel with surface defects of different depths and rotary angles. With an additional sensing coil for the designed EC sensor, the defect angle (or orientation) can be measured without spatially and coaxially rotating the excitation coil. By referring to the voltage change (due to the defect) diagram (voltage sum versus voltage different) of two sensing pairs, the rotary angle of the surface crack is retrieved with a maximum residual deviation of 3.5 %.