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Iowa State University

Electrical and Computer Engineering

Eddy Current Probes

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An Analytical Model Of A Ferrite-Cored Inductor Used As An Eddy Current Probe, John R. Bowler, Yi Lu, Theodoros P. Theodoulidis Jan 2012

An Analytical Model Of A Ferrite-Cored Inductor Used As An Eddy Current Probe, John R. Bowler, Yi Lu, Theodoros P. Theodoulidis

John R. Bowler

An analytical model of an axisymmetric eddy current ferrite-cored probe above a multi-layered conducting half-space has been developed using a procedure in which the domain of the problem is truncated radially. This means that solutions can be expressed in the form of generalized Fourier-Bessel series. The expansion coefficients are found by matching the field across the interfaces between the subregions of the problem. Initially, the magnetic vector potential of a simple circular current filament is expanded in a series form. The solution is then modified to accommodate an infinitely long coaxial ferrite core, and the principle of superposition is invoked …


Analysis Of Arc-Electrode Capacitive Sensors For Characterization Of Dielectric Cylindrical Rods, Tianming Chen, Nicola Bowler, John R. Bowler Jan 2012

Analysis Of Arc-Electrode Capacitive Sensors For Characterization Of Dielectric Cylindrical Rods, Tianming Chen, Nicola Bowler, John R. Bowler

John R. Bowler

An arc-electrode capacitive sensor has been developed for quantitative characterization of permittivity of cylindrical dielectric rods. The material property of the cylindrical test piece can be inversely determined from the sensor output capacitance based on a theoretical model. For the modeling process, the electrostatic Green’s function due to a point source exterior to a dielectric rod is derived. The sensor output capacitance is numerically calculated using the method of moments (MoM), in which the integral equation is set up based on the electrostatic Green’s function. Numerical calculations on sensor configuration optimization are performed. Calculations also demonstrate the quantitative relationship between …