| Magneto-optical recording has the advantage of both magnetic recording and light recording. With the development of the magneto-optical material theory and the preparing methods, the researches on measurement of magneto-optical characteristic are very important. In order to come to the requests of the measurement, the design of the sweep magnetic field circuit and the computer-aided software are discussed in this thesis.The sweep field circuit had been designed with the core of the MCU 80C196KC and peripheral circuit, forming a feedback closed-loop to control magnetic field: The analog signal of magnetic field measured by hall element is changed to digital form by A/D converter, and then it is compared with a standard digital triangular wave which is produced by programming. The duty ratio of the PWM signal is adjusted according to the result of the comparing. The PWM signal is used to drive the IGBT of the bridge circuit to modulate the current of electromagnetic coil, and then the magnetic strength is modulated, causing the waveform of the magnetic field to be identical with the standard digital triangle wave.Computer aided testing software draw a kerr hysteresis loop based on the magnetic strength and the kerr angle signal which is collected by the computer in the same coordinate system, and then we can calculated the kerr angel and the coercive force of the samples being tested, outputting the results and reflectivity together. Multiple data preservation formats definitely meet the requirements of data exchanging and processing.The measuring instrument designed successfully has been applied to attain the characteristic of commercial MO discs. The result of the measurement indicates that the measuring system is satisfiable for science research and teaching experiment. |
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