Research On AC Impedance Measurement System And Its Electromagnetic Compatibility Based On Steady Magnetic Field

Multiferroic materials with both of magnetic ordering and ferroelectric ordering have wide research value and technical applications in the future. Accordingly, the properties of magnetoelectric coupling are attended generally by people recently. In addition, the AC impedance measurements are able to explore the internal microstructure and the conductive mechanism of the material. Research on Magnetoelectric coupling properties of these kinds of materials plays an important role in Materials Science field. Therefore, an AC impedance measurement system based on the steady-state magnetic field is designed and built for exploring the related issues about Material Science.The main contents are as follows:The principles and basic formulas of the AC impedance measurements are presented. Furthermore, the calculation method of dielectric constant and drawing method of Cole-Cole circle is are presented. The basic components of the measurement system are introduced. Connection methods, functions, models, performance parameters of each part of system are presented.Measurement problems encountered during the entire measurement are presented, the design of the sample rod is proposed pertinently. The measurement results affected by the standing wave and the principle of changing of transmission line parameters are researched. The reasons and solutions of High frequency compensation calibration in Precision Impedance Analyzer can not pass are discussed. A4+1transmission line model based on multi-conductor model is created. Under different assumptions about shield layer, the parameters of per-unit-length transmission line are calculated and the predictions of this system are proposed. That the actual measurement result consistent with the predictions verifies the correctness of the circuit model. Furthermore, a simulation in electric field and magnetic field about this model is presented.According to may be the pathway of measurement system by EMI, the measurement system includes power supply, precision impedance analyzer, inside and outside transmission lines, samples rod connector holder, sample holder. Conducted interference and radiated interference problems in these parts are detailed researched respectively. For the characteristics of common, differential mode interference and open, shorted circuit, the interference path model is created, and the formulas of it are derived. According to the characteristics of the measurement system, the detection method of EMI signal and the spectral analysis of the measurement signal are given. The shield connection and the preparation method of the sample electrode are present. The EMC reliability of the measurement system has been verified.The structure of software system is present by integrating the hardware system. The software operating characteristics when precision impedance analyzer and PPMS were at work are analyzed. Furthermore, data storage algorithms, communication algorithms, synchronization algorithms of the software system are present. The use and process of the software system exemplified by the UI of it are present.Finally, the frequency, the magnetic field and the temperature dependence of the measurement data are given. The curves of dielectric constant and Cole-Cole circle impedance are given according to the formulas. And the experimental results are analyzed.