Research And Implementation Of SEP Transmitter GPS Time Synchronization And Data Acquisition And Processing System

Controlled Source Audio-frequency Magnetotelluric(CSAMT), controlled source audio frequency magnetotelluric method is a kind of artificial source frequency domain electromagnetic sounding method, with a wide range of exploration depth, high measurement efficiency and other advantages, which has been widely used in ore prospecting, groundwater detection, environmental pollution detection, oil exploration, engineering geological exploration and other fields. Artificial source electromagnetic exploration system consists of a transmitter and a receiver, the transmitter responsible for providing pulse current to the earth as its source of power; the receiver receives magnetotelluric response information efficiently, and then through the geophysical inversion original observation into geophysical model data, which can reflect the geological condition. As the controlled source electromagnetic excitation field source, the development of Surface Electromagnetics Prospecting(SEP) transmitter is an important part of the research in electromagnetic prospecting.(Global Positioning System(GPS) time synchronization and data acquisition and processing system is an important part of the overall SEP transmitter system, whose main function is to provide accurate GPS time synchronization of transmitter, real-time acquisition and processing of transmitting voltage, current, frequency data, and these data will be uploaded to the host computer display and storage.This paper study the theoretical analysis, hardware and software design and experimental verification of GPS time synchronization and data acquisition and processing system, and complete a low noise, low drift, high precision SEP transmitter GPS time synchronization and data acquisition and processing system based on DSP and FPGA. The main work of this paper includes four parts:The first part designs the GPS time synchronization module. Fristly, analysis of the principle of GPS timing and the source of GPS timing error, in view of the problem of GPS losing lock, proposing the use of GPS/local clock dual-mode timing synchronization technology, the overall design scheme and principle of time synchronization system is presented, and describes each functional module to achieve the function; secondly, the time synchronization scheme of hardware and software designed in detail, focusing on the methods of OCXO frequency correction and timing work mode switch; at the end of the time synchronization precision of experimental verification and analysis.The second part designs the data acquisition and processing module. Firstly, the overall design scheme and the principle of data acquisition and processing system is presented, using DSP and FPGA as the main controller, the transmitting voltage, current and frequency of real-time measurement and display; secondly, describes the data acquisition and processing system hardware and software design process; finally focus the method of transmitting voltage, current, frequency signal processing by DSP and frequency measurement by FPGA.The third part designs the human-computer interface. A good man-machine interface is designed by using Labview software, which can online configuration transmitter work mode and emission parameters, and has dual functions of data display and waveform display, real-time monitoring the operation status of the transmitter, in addition also has automatic storage function to post-data analysis.The fourth part accomplishes experimental verification. The experiment of GPS time synchronization precision and data acquisition system sampling accuracy are completed in the laboratory, the experiment results show that the synchronization accuracy is improved up to ±0.1μs and the sampling precision of data acquisition and processing system can reach more than 99%, meet the design requirements of the system. Finally, through the transmitting contrast experiments outdoors with the foreign advanced and representative transmitter, by the quality of the transmitting frequency, the design of the transmitter being close to representative of foreign advanced level transmitter is verified. The outdoors geological exploration experiments show that the performance of electromagnetic transmitter which designed in this paper can be competent for the outdoor geological exploration.