Transient Electromagnetic Full-wave Exploration And Design Of Data Acquisition System

Transient electromagnetic full-wave exploration needs to record the whole process of transient response when the power supply electrode or coil is forward turn on,forward turn off,reverse turn on and reverse turn off.Multiple groups of transient response signals at different locations need to be recorded synchronously.These signals have small amplitude.So we need high precision,high resolution and multi-channel data acquisition system to acquire the transient response.In this paper,we designed the data acquisition system for transient electromagnetic full-wave exploration,which was mainly used for geological exploration of shallow surface.Based on the transient electromagnetic theory,we designed the potential function by maxwell's equations and the axial symmetry of the electromagnetic field excited by the electrode.We derived and calculated the transient electromagnetic field response of electrode excitation,obtained the transient electromagnetic response waveform and the spatial distribution of the transient electromagnetic field,which provided theoretical guidance for the design of sampling distance of transient electromagnetic full-wave exploration data acquisitionIn terms of hardware and software design,we designed four data acquisition systems under different application scenarios based on a high resolution ADC with24-bit precision.Including 8 channels high resolution data acquisition system based on ARM and ADS1278;32 channels high resolution data acquisition system based on ARM and ADS1278;64 channels high resolution data acquisition system based on FPGA and ADS1278;8 channels high resolution remote data acquisition system based on FPGA and ADS1278.Each data acquisition system designed corresponding software programs and computer software for receiving data according to the actual application environment.Each data acquisition system realized the function of data sampling,conversion,storage and transmission.We tested the data acquisition system in the laboratory and carried out field test verification at the construction site.All the four data acquisition systems can accurately and effectively acquire transient electromagnetic response signals,which can meet practical applications.