Research Of Half-airborne Electromagnetic Transmitter

Half-airborne electromagnetic method geophysical survey equipment hasprominent advantages of fast, flexible and efficient, and can perform geologicalexploration mission in the mountains, hills and other complex surface environment.Foreign countries have successful developed half-airborne electromagnetic methodsurvey system and made a series of research results, but china`s research in thisdirection is still l in the initial stage. Half-airborne electromagnetic survey systemcomposed of transmitter system and the receiver system. Since the1980s, a greatamount of work has been done from theory to practice in the field of electricalsurvey.Good result has been achieved in search for metal mine and groundwater, alsoin surveying engineering geology and gas exploration in special surface environment.Its theory and apparatus are improved and innovated continuously. To design ahalf-airborne electromagnetic method survey system for geological exploration underspecial environment becomes more and more important. This paper draws onthe design idea of the existing half-airborne electromagnetic method surveytransmitter, combined with the design of digital circuit design, design the hardware ofhalf-airborne electromagnetic transmitter, and carried out experimental studies.Based on the electromagnetic theory, this paper analyzed the characteristicsof the typical and representative electromagnetic instruments and researched thecurrent situation of domestic and international research and the lack oftransmitter, and expounds the development trend of half-airborne electromagneticsurvey transmitter. This paper puts forward a new design idea: using CPLD and singlechip microcomputer as the core design, the whole system is divided into controlcircuit, drive circuit, data acquisition circuit, power circuit and other circuit, draw thePCB, do the related experiment.According the index of the requirement of the transmitter system, the paper putsforward the theoretical basis of half-airborne electromagnetic transmitter and relevanttechnical indexes. The power components selected the IGBT power thyristor asswitching devices through the analysis of working conditions, selected photoelectriccoupler as isolated drive circuit and other components.51SCM is used as the core of the main control unit, combined with peripheral circuit control signal acquisition circuit, drive circuit, drive signal generation,modulation and display. This paper implements sampling circuit sample driver circuitsignal value of the voltage, electric current and so on. System is given the related keytechnical requirements of the device, and presents the related principle diagram andthe signal waveform.Current overshoot diminished unit is designed for the emission peak currentchanges. The unit`s analog signal from the current transformer output first passesthrough the peak detector circuit and is converted to DC level signal. The control unithardware adopts51single chip minimum system as the core, periphery, sometimesthe end chip, AD chip, EEPROM memory chip. The application of modular analogsignal and the time of current collection was designed, what more AD conversion,recording, storing and displaying function.The main circuit of IGBT driving circuit is designed. At the same time, improvedthe driving circuit of control switch, adopting photoelectric coupler isolation maincontrol circuit, to reduce the influence of high voltage to the weak current.