| Time Domain electromagnetic Method, or which called Transient Electromagnetic methods (TEM), are some kind of electrical discrepancy based on target. It utilizes re-line untouched to ground or re-line touched to ground to transmit once pulse magnetic field toward the underground. In the period of the first field's intermission, measures the induced electromagnetic field (the second field) changed with time which is created by underground substance. So it can measure the position of underground inhomogeneous substance and estimate its scale and electricity capability. This method can be applied in al-most every field of geophysical exploration: ore exploration, constitution exploration, hydrogeology and engineering geology investigation, environment survey supervising and archaeology and so on. It is one of the geophysical exploration methods which develop faster.ATTEM-II transient electromagnetic detection system designed by Jilin University 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 abroad. But the receiver used internal hardware integrated operating system, the keyboard and LCD as input and output interfaces, achieved the operations such as system parameter settings, acquisition and control, graphic display and so on. The system had a complex structure and cumbersome connections, was large in size. And it is difficult to carry and make a cumbersome, inconvenient measurement. Hence, the new generation of DSP-based transient electromagnetic receiver is designed and data transmission and processing of the transient electromagnetic receiver based on the Bluetooth is presented.The content of the receiver wireless communication consist of data packets and command packets, the size is between several KB and a few tens or hundreds of KB. And data transmission rate of the system is relatively low, the Bluetooth serial communication is required. And the client is Pocket PC, the server is the Bluetooth module which is connected to the receiver. Baud rate of data transmission is 9600bps, which can be set up by people. In order to test Bluetooth module, a lot of experiments on data, string, file-transmission have been made and the results show that the Bluetooth module with the baud rate for 9600 to 57600 bps can work and error rate is at±0.02%.Using the Windows Mobile 5.0 SDK, Pocket PC applications can be designed in the Visual Studio 2005 environment. By using them, users can set up parameters, control acquisition and data transmission, make data processing and draw the transient signals. And the data can be on-site assessment. To develop Bluetooth Protocol in the Windows Mobile environment, it is necessary to install WIDCOMM BTW-CE SDK which provides specific categories and the related functions. The CBtlf category and CSppServer category are used to develop RFCOMM protocol which can establish a virtual Bluetooth serial port and set up a data link connection. The CPSerialPort category is designed to repackage the serial API functions. By using it and its functions, a thread is used to realize the serial communication. Experiments have proved the application can enumerate the working Bluetooth devices and their service, establish a virtual serial port and set up a data link connection and the serial communication can work. Using recursive algorithm, a data revivification method is designed to convert the ASCII strings sent by the receiver to be decimal numbers which are sent into the deposited arrays. The application can judge if the data are correct and process data later. To recognize and correct the singular point caused by the floating-point design in receiver's hardware, and better to preserve the original signal details, a method based on the median deviation and the quantile distribution diagram is presented to identify and correct the large singular points. For the small burrs after singularity processing, the arithmetic average repeatedly and three-point filtering denoising algorithm are used to smooth the transient signal curves. Those test results show it not only can effectively remove large singular points, draw smooth curves better, but also preserve the original signal details. The functions of CClientDC category provided by GDI are used to draw curves, and acquisition parameters and the data are deposited in a".txt"file with the name of the point working.In order to test the receiver based on Bluetooth, the paper shows the performance test and experiment results. It includes performance index, model experiment and field results. The performance test includes Bluetooth transmission distance, short circuit noise test, transient electromagnetic curves compare made in the same measurement conditions and so on. The results show that Pocket PC can control the receiver through Bluetooth wireless communication within 10 meters, realize the functions which include parameter settings, acquisition control, data transmission, graphic preservation and so on, complete the actual survey measures, and the overall short circuit noise of the new receiver is relatively smaller. The model experiment and field results include online result between receiver and transmitter, and draw-out curves analysis which can accurately reflect the location of the abnormal. The results indicate that the equipment has the good stability and the usability.Finally, sum up the work of the paper, analysis the existing problems, make further suggestions for improvements about how to relief Bluetooth spurious noise, increase Pocket PC functions and so on. |
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