Location

La Jolla, CA

Start Date

1-1-1993 12:00 AM

Description

By resolving Maxwell’s Equations for the case of a long coil encircling a galvanized wire (fig.l), we can calculate the normalized impedance diagram. Later, during the experiments, we will directly use this diagram to find the thickness of the zinc layer. Before resolving Maxwell’s Equations, a few words about the normalized impedance diagram in general. Figure 2 shows the normalized impedance diagram for the simple case of a long coil encircling a wire made out of a homogeneous conductive material of permeability µr and with a fill factor equal to one. A fill factor, η=a2/c2 (fig. 3), equal to one, means that there is no air between the coil and the wire. The x axis represents the normalized resistance (1) (Rp−Re)/ωLe, where Rp is the real component of the impedance Zp of the coil when there is a part inside the coil, Re and ωLe are respectively the real and the imaginary components of Ze when the coil is empty.

Book Title

Review of Progress in Quantitative Nondestructive Evaluation

Volume

12B

Chapter

Chapter 6: Material Properties

Section

Thin Films and Coatings

Pages

1947-1953

DOI

10.1007/978-1-4615-2848-7_249

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

Eddy Current Thickness Measurement of the Zink Layer on Galvanized Steel Wires

La Jolla, CA

By resolving Maxwell’s Equations for the case of a long coil encircling a galvanized wire (fig.l), we can calculate the normalized impedance diagram. Later, during the experiments, we will directly use this diagram to find the thickness of the zinc layer. Before resolving Maxwell’s Equations, a few words about the normalized impedance diagram in general. Figure 2 shows the normalized impedance diagram for the simple case of a long coil encircling a wire made out of a homogeneous conductive material of permeability µr and with a fill factor equal to one. A fill factor, η=a2/c2 (fig. 3), equal to one, means that there is no air between the coil and the wire. The x axis represents the normalized resistance (1) (Rp−Re)/ωLe, where Rp is the real component of the impedance Zp of the coil when there is a part inside the coil, Re and ωLe are respectively the real and the imaginary components of Ze when the coil is empty.