Measuring resistivity in a contactless fashion

Sammanfattning: The aim of this thesis work was to develop a rig to measure the resistivity of a metal sample. The initial testing of the rig would be done at room temperature and calibration of the setup would be done with aluminum samples and then metallic alloys would be studied. The method implemented is a contactless one where the diffusion of eddy currents in a sample is measured by a coil and the resistivity can be deduced. The eddy currents are induced by a pulsed magnetic field and the diffusion of the currents in the sample is due to the resistance of the sample material. This method is the same as that described by C.P. Bean in 1959. To facilitate the construction of the coils, a coil winding rig was designed and built. In conjunction with this, calculations were made to approximate the resonant circuitry to simplify tuning of that circuitry at a later stage. Once the preliminary measuring rig was set up, extensive testing, configuration and calibration of the rig was conducted. This was done with and without a test sample of aluminum rod present inside the rig. The goal of this was to eliminate unwanted interference between different components involved in the experiment and to resolve the measurement of the diffusing eddy currents. In this thesis, limiting factors of the functionality of the experiment setup are explored. The induction of eddy currents in the sample is strongly dependent on the amount of magnetic flux and its rapid change. The change in magnetic field density, going from maximum to zero, took place over the course of microseconds, which was fast enough but the maximum field strength seen was to small to induce sufficient eddy currents for reliable measurements.