RResearch and development of algorithm for determination of absolute conductivity value without calibration by eddy current techniques
Final Report Abstract
The determination of the electrical conductivity of solid objects and thin layer systems using inductive eddy current testing methods is a widely used procedure, but it is based on an empirical approach. Using reference samples with varying conductivity, a calibration curve is established, which forms the basis for determining unknown conductivities. This calibration is only valid for one device, for one frequency, and mostly for a very limited range of sensor distance, and must be individually determined for each material system to be measured. In this project, a new principle was proposed and investigated, which allows conductivity to be derived directly from eddy current measurements based on the physical laws of the electromagnetic field, eliminating the need for empirical calibration curves in the future. For this purpose, an eddy current testing electronics based on the EddyCus® system platform was modified, allowing not only the voltage in the receiving coil to be measured but also the current in the exciting coil. As a result, it is possible to directly output the electrical impedance of the measuring set, consisting of a measuring coil and the object to be measured. Through extensive analysis of effects within the measuring coil, it was possible to eliminate the coil influences, so that in the end, the independent determination of the electrical impedance of the object to be characterized can be output as an absolute value without individual calibration curves. The project part processed by Fraunhofer IKTS and the results obtained from it have now been integrated into the EddyCus® system platform and represent an improvement of the product properties. In the Wensch sub-project, the following approaches and resulting tasks were pursued. • Numerical simulation of Maxwell's equations with the Comsol package as well as with specially developed FE packages in the presence of thin layers with materials of different permeability and permittivity. • Generation of reference data from numerical experiments. • Comparison with experimental data. • Estimation of material parameters using the results of the numerical simulations. At the beginning of the project, simulations of Maxwell's equations were carried out after studying the relevant literature. The professional software package Comsol was used, and we also used the university package SOFE by Dr. Lars Ludwig. For evaluation, the TEAM test set was used, where the results with SOFE could be verified. For TEAM 7, the results could be verified overall. In further project phases, numerical data were generated, and experimental data were also successfully produced.
Publications
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Study of a Particle Based Films Cure Process by High-Frequency Eddy Current Spectroscopy. Coatings, 7(1), 3.
Patsora, Iryna; Heuer, Henning; Hillmann, Susanne & Tatarchuk, Dmytro
