Jacek Salach

Sensitivity and Offset Voltage Testing in the Hall-Effect Sensors Made of Graphene

Paper presents the results of the hall effect testing in the graphene structures. Special hall effect structures were designed and build, using large graphene sheets. Laboratory testing stand was developed to test sensitivity and offset voltage in hall effect structures under external magnetic field. Characteristics of investigated structures were measured, including such impacting factors as structure size, external magnetic field strength, temperature and time.

Low Current Transformer Utilizing Co-Based Amorphous Alloys

Metal oxide surge arresters have been widely used for protection of power system networks against overvoltages caused by atmospheric discharges or malfunction of devices connected to the network. During its operation, a surge arrester structure is degradated, which can be observed as an increase of a surge arrester leakage current. This paper presents an implementation of a new, high-permeability, Co64Fe4Ni1Si15B14 amorphous alloy as a current transformer for monitoring of a leakage current in low voltage surge arresters. The characteristics of the current transformer for different loads have been measured in the system using very sensitive current-voltage converter. Experimental results confirmed that low current transformer utilizing Co64Fe4Ni1Si15B14 amorphous alloy in annealed state gives a possibility to measure a leakage current about several μA with operating frequency 50 Hz. Moreover, the results indicate that the leakage current waveforms have a different shape than a pure sine wave voltage applied to the surge arrester enabling an evaluation of the device nonlinearity as a measure of its degradation by means of a resistive component of the leakage current.

Two-Axis, Miniature Fluxgate Sensors

Miniature fluxgate sensors are recently intensively developed and have become a valuable alternative to other magnetic sensors types. Presented two-axis miniature fluxgate sensors show new opportunities for further miniaturization of fluxgate magnetometers. Frame-shaped amorphous alloys cores for the sensors were etched from 25 μm-thick tape. Sensors were made in printed circuit board (PCB) multilayer technology. Sensors with Fe-based and Co-based cores were tested for different values of constant magnetic field in two directions. Experimental results confirmed their ability to accurately obtain two directional magnetic field measurements.

Application of Extended Jiles–Atherton Model for Modeling the Magnetic Characteristics of Fe

This paper presents the result of modeling the magnetic characteristics of ring-shaped cores made of Fe41.5Co41.5Nb3Cu1B13 alloy in both as-quenched and nanocrystalline state. For the modeling, the extended Jiles-Atherton model was used. Extension of Jiles-Atherton model is focused on taking into account the changes of parameter k caused by changes of the average energy required to break pinning site. Determination of models parameters was made on the base of optimization process. This optimization covered both evolutionary strategies and simulated annealing. Finally, good agreement between experimental characteristics and the results of modeling was achieved. This agreement is confirmed by the high value of R2 determination coefficient, which exceeds 99% for both as-quenched and annealed cores. As a result, it was confirmed that the presented method of modeling the magnetic characteristics of Fe41.5Co41.5Nb3Cu1B13 alloy in both as-quenched and nanocrystalline state is suitable for technical applications.

_{41.5}

The paper presents the aim, way of proceeding and results obtained during the research made in the project GRAPHTRIB to determine the metallic substrates, other than copper, to realize graphene growth process. The various silicon and silicon free bronzes were the objects of investigations. The obtained results presented in the paper aren’t encouraging.

Co

Paper presents the results of application of Whitney elements based method for performing the forward transformation in eddy current tomography. Accuracy and the noise level of such a forward transformation is the most important factor determining efficiency and metrological properties of eddy current tomography. Comparison of the experimental results of measurements on eddy current tomography test stand, and results of modelling utilizing Whitney elements indicated high accuracy of modelling. However, results of modelling present unacceptable noise level. Sources of this noise are analysed in the paper, indicating the guidelines to overcome this barrier.

_{41.5}

Idea of the high-resolution eddy current tomography is presented. Proposed system gives possibility of cylinder-shaped elements made of both magnetic and non-magnetic materials testing. To validate the concept, the tomographic measurements were carried out on set of steel cylinders with non-magnetic copper inclusion. Measurements were done during both linear and rotational movement of the element. Achieved results indicate the high sensitivity of system, which creates possibility of its application for non-destructive testing of the elements made of ferromagnetic and non-magnetic materials.

Nb

Paper presents the digitally controlled high resolution DC current transformer enabling contactless measurements of DC current. To increase the sensitivity of current transformer, high permeability, amorphous alloy based ring-shaped core was used. Moreover, analyses of magnetic field distribution in the measuring gap were carried out. Magnetic field in this gap was measured by the hall sensor connected with the high resolution sigma-delta analog to digital converter. As a result, current up to 100 A may be measured with uncertainty of about 1A.

_{3}

Paper presents the frame-shaped cores based methodology of testing of magnetoelastic characteristics of energetic steels such as X30Cr13 steel, subjected to tensile stresses. In presented method, the magnetic circuit of the sample is closed. For this reason, the results of magnetoelastic investigation are independent of the shape of the sample. To validate the proposed method, the influence of tensile stresses on B(H) hysteresis loop of X30Cr13 martensitic corrosion resistant steel was carried out. On the base of these result, clear criteria for non-destructive assessment of mechanical stresses in the material were determined.

Cu

This paper presents an eddy current tomography setup with high spatial resolution and high accuracy of measurements of the signal on the detection coil. In the proposed solution both amplitude and phase shift are measured, which makes it possible to calculate the spatial distribution of both permeability and resistivity of the tested element. As a result, the setup presented here creates the possibility of effective detection of discontinuities in cylindrical elements, which opens new possibilities for industrial applications of eddy current tomography.