Research And Implementation Of Anti-interference Ultra High Density Electrical Prospecting Instrument Based On Full-Waveform Sampling

Electrical prospecting is a geological exploration method for geological identification by observing the differences in electromagnetic and electrochemical properties between various underground rocks(ores)in an artificial electromagnetic field.Electrical exploration instrument provides underground exploration information,geophysical prospectors use geological data and stratum structure to judge the possibility of underground minerals and provide drilling verification solutions.The instrument can also provides scientific and reliable underground construction information for urban engineering,underground engineering,water conservancy projects,as well as reference materials for engineering construction programs.The traditional time-domain induced polarization method has the disadvantages of large transmission power,sparse measuring point density,less exploration information,weak anti-interference ability,and low resolution.This thesis analyzes and compares the performance of electrical prospecting instruments domestic and overseas,and combines the development of large-depth exploration and high-resolution trends,and designs an anti-interference ultra-high density electrical prospecting instrument based on full waveform sampling.This instrument effectively combines the advantages of high-efficiency exploration and rich geological information in the high-density electrical exploration with the characteristics of low-power transmission(600W)and strong anti-interference ability in the frequency domain electrical exploration.Arranging electrodes at one time can achieve a combination of multiple electrode arrangements,so as to obtain a wealth of information about the geoelectric structure;The receiving circuit board is designed as a daisy chaining structure to realize parallel and high-efficiency collection of prospecting information;The custom multi-frequency transmission waveform not only meets the frequency domain exploration requirements,but also can use the pseudo-random inverse M sequence code to improve the system identification and anti-interference ability;Using FPGA and ARM dual processors to work together to improve the parallel processing capability and work efficiency of the instrument;SDRAM(DDR3)and asynchronous FIFO are used to buffer the sampled data of parallel multi-channels,and play a role in optimizing data link transmission without losing data during long-term exploration.In the thesis,the basic exploration principle of ultra-high density electrical prospecting in time-frequency domain is studied,and the reason of electromagnetic induction coupling effect is analyzed.Through the analysis of the anti-interference ability of the transmitted signal,it is proved that the pseudo-random sequence has the relevant identification and anti-interference ability,and is suitable for the transmission signal of the electric exploration instrument.Combining the pseudo-random autocorrelation identification capability with the frequency domain exploration method,a customized multi-frequency transmission signal is defined.Under the excitation of the self-defined multi-frequency signal,a method to improve the exploration depth is proposed by analyzing the characteristics of the instrument sampling system.This method combines the characteristics of full waveform input and output sampling,adopts LMS adaptive algorithm and differential recursive RLS algorithm to eliminate noise and information extraction of the collected data,realizes the extraction of useful information for exploration under low signal-to-noise ratio,thereby increasing the exploration depth.Carried out the research and development of the instrument,completed the system hardware circuit design,PCB design,hardware debugging,software driver design,timing simulation and board-level verification tasks.The instrument has carried out emission signal test,system noise test,sampling accuracy and electrode switching test,verifying that the various performance indicators of the instrument have reached the expected set standards.Finally,an outdoor exploration experiment was carried out.By analyzing the frequency characteristics of experimental exploration data and observing the distribution of induced polarization effect and electromagnetic coupling effect,it proved that the instrument has practical application value.