Reconstructing Electrical Conductivity Profiles from Variable-Frequency Eddy Current Measurements

Determining The Step-Change Conductivity Profiles Within Layered Metal Structures Using Inductance Spectroscopy

“…Equations (1)(2)(3)(4)(5)(6)(7)(8) are an accurate description of the forward problem. However, to evaluate them in practice involves integration over a large zone and the computation process is slow.…”

“…One approach is to measure the direct current (DC) impedance map and estimate the conductivity [1][2]. Another approach is eddy current inspection, which infers the conductivity profile from impedance (or inductance) data [3][4][5][6][7][8][9]. The principle of these inverse methods [5][6][7][8][9] is to fit the inductance data (measured or simulated) to a complete analytical solution using simplex search.…”

Measuring Thickness and Conductivity of Metallic Layers with Eddy Currents

“…However, this term cance1s when the difference between ZL and ZHSP is taken. The impedance difference can be ca1cu1ated from Dodd and Deeds formu1a as (2) where (3) (4) Figure 2 shows a comparison of theory and measurements made with an air core probe for the real part of the impedance. The curves shown in Fig.…”

“…Previously Kahn and Norton [2] have considered a similar problem involving concentric cylinc1ers with an encircling coil. They also used a least-squares norm and obtained good results for their chosen applications.…”

Determination of Electrical Conductivity Profiles from Multi-Frequency Impedance Measurements

“…A more detailed description of the leastsquares algorithm and an analytical solution to the forward problem for an axisymmetric layered sample can be found in ref. 1.…”