| With the rapid development of industry and technology, electronic equipments have been flooded to the industrial and agricultural production, national defense and all respects of personal life. At the same time, electronic equipments become necessities that cannot be neglected. However, when these equipments are used in convenience and enjoyment, they also bring a lot of negative effects, in which the electromagnetic radiation generated by these equipments could cause disease to human health. A large number of epidemiological data suggest that long-term exposure in low-intensity ACMF would have negative effects on human health. Therefore,the measurement of ACMF has become one of the hot topics of measurement of magnetic field. Not only it is essential that research on this respect can make people aware of their own health, but also can quantify the impact of ACMF to make people have a concept that what extent of ACMF is harmful for health.After reading large amounts of data and on the basis of understanding basic method of measuring ACMF, and according to the current measurement needs and laboratory conditions, three kinds of methods are suitable for measurement of ACMF: electromagnetic induction, Hall effect and magnetostriciton. Aimed at the advantages, disadvantages and current technology level, Researches are focused on electromagnetic induction and Hall-effect to design the structure of sensor and signal conditioning circuit. Combined with the above two principles, the measurement of ACMF that have a frequent range of 0-500Hz, field strength range of 0-10Gs are achieved. The measuring theory which based on magnetostriction is researched, and a measuring solution is proposed. Meanwhile, low-power microcontroller MSP430 is used as the core for the design of the relevant measuring circuit, which achieved the exciting of sensor, conditioning of output signal, data acquisition, storage and display.With the using of standard magnetic field generation device-Helmholtz coils, data processing and comparison are made between the data from Helmholtz coils and the data from measurement: although Hall-effect has a greater error, the measurement of frequency is wide; the electromagnetic induction has a greater sensitivity when the frequency of ACMF increases. It is found that electromagnetic induction is suitable for measuring the low frequent ACMF that the frequent is higher than 500Hz. And the characters of the two methods and the error sources are analyzed. According to the existing calibration method, the preliminary calibration is made for the sensors that designed. And these sensors already met the requirement of measuring the ACMF of living environment. |
