| Transient Electromagnetic methods can be called as Time Domain Electromagnetic methods ,which is abbreviated to TEM or TDEM. It uses no grounding lines or grounding electrode to send the first field, in the interim period of the first field, measures the changes of the secondary field with time, thereby detects underground uneven body position, and estimates that its size and conductive properties. In recent years, it has developed rapidly both at home and abroad, TEM can resolve a large range of geology problems which almost includes every field of geophysical exploration including air and sea, and achieves remarkable results, so TEM has already become an indispensable method of geophysical exploration.General transient electromagnetic method equipments include two parts: the transmitting system and the receiving system. The task of transmitting system is to transmit various current excitation signals for the electromagnetic method's exploration. Current excitation signal requirements have enough power, short shutdown time, and transmitting system can show stabile current value and the current off-time , records current falling edge and so on .ATTEM-II transient electromagnetic detection system, which is designed by Jilin University Intelligent Instrument and Control Institute of Technology, and has been used to make many experiments such as in groundwater investigation of Inner Mongolia and empty area detection of Zhoushan and so on. The results show that the effect has reached the advanced level. However, as design time earlier, some functions are lack slightly, ATEM-II transmitting system are need for improvements.On the basis of two models of the electromagnetic transmitting system-ATEM-II and ERT ,designs improved transmitting system whose control chip is MSP430F149.MSP430F149 with 60K ROM, 2K RAM , is in favor of a software upgrade; Timer capture / compare modules are easy to achieve PWM outputs, do not require auxiliary devices, simplify the system, improve the anti-jamming of system; Transmitting system increases three kinds of pseudo-random waveform and dual-frequency emission , uses the keyboard interrupt work and improves the efficiency of the transmitting system.Paper presents the development of the H-bridge in the transient electromagnetic transmitting system ,and gives design principle, compares two IGBT drivers, in conjunction with the system to select the best one.The absorption protection circuit is to ensure transmitting system stability. Most of absorption use hardware shutdown circuit, the paper presents several hardware shutdown circuit's features, and in accordance with the absorption characteristics to choose suitable circuit. Some TEM transmitting systems are free shutdown, the shutdown function uncertain, causes shallow blind spot detection and data interpretation inconvenience, the paper also discusses an absorb circuit with a current high linearity shutdown which called energy-dissipation quasi-resonant rectifying circuit and presents the experimental results.Typical TEM data processing is that receiving system records signal of sensor when emission current is completely shutdown zero, this results have a blind spot which measures from the surface down to10 meters. In order to enhance the scope of observation, reduce detection blind spots, deduct the first field from the total market. The first field strength is calculated from the record shutdown of the emission current waveform. Current records of the system use FIFO and high-speed AD as core, make AD working under CPLD controlling ,in the end of the sampling ,use MCU to read out the data , process, storage and communicate.The system test results are presented in the latter part of Papers, including the transmitting waveform, the current recording, the experiment of the current shutdown and the tests of field, giving the cause of the test results. The system meets the design requirements from the test results seeing.At last, summarizing the content of thesis and the work within the two-year master study and giving the next research advice.
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