Study And Correction Method Of Portable Time-domain Electromagnetic Receiver

The detection system based on time domain electromagnetic method has beenwidely used in geophysical detection fields and has become one of the majorgeophysical methods of water inrush detection in underground mines, tunnels andother limited space. Since it can counteract the electromagnetic interference,distinguish low resistance accurately and reach further distance, this system hasachieved good results in practical applications. However there are still some problemsto be solved, for instance, the time-domain electromagnetic systems always encounter magnitude deviation between the attenuation curve and the theoretical curve, and italso has calibration problems of the detection accuracy and resolution.To solve the above problems, at first, we analyze the characteristics of thetime-domain electromagnetic responses. Based on the portable receiver independentlydeveloped by Jilin University, we design the standard time-domain electromagneticsource, and calibrate the receiver with the standard source. Obtaining the error, wecan further analyze its generated reasons and improve the system’s measurementaccuracy. The main contents of this paper are as follows:(1) Based on electromagnetic principles,we have studied the time-domainelectromagnetic response formulas in homogeneous half space and layered earth, etc.Summarizing the response equation, we have deduced standard theoretical formulasof time-domain electromagnetic source, and have explained how to implement theoutput standard source byARM.(2) We have introduced the basic principles and construction of the portablereceiver, and have analyzed the major issue and its causes.(3) We have developed a standard time-domain electromagnetic source, andperformed its performance test analysis.The result showed that it has reached aresolution ratio of100μV. (4) Through the joint test and correction of the time-domain electromagneticsource and the receiver, the resolving power of the receiver we calibrated is100μV.In this paper, we develop the standard time-domain electromagnetic source andcomplete the receiver calibration and correction.Through a large number ofexperiments, we calibrate the performance of the receiver, analyze correct andcalculate the error sources, which provides valuable experience for high-precisioninstrument calibration and error analysis.