Research Of Data Acquisition Key Technologies Of Half Aviation Electromagnetic Exploration System

Half aviation transient electromagnetic method is a commonly used geophysical exploration method, which installs the aviation electromagnetic system in the unmanned aerial vehicle or other flight vehicles, by observing the abnormal electromagnetic fields produced by instruments inspiring or induced by natural form of electromagnetic fields, or individually observing the abnormal electromagnetic field induced by geological body, for the purpose of seeking the mineral resource or solve some geological problems, with the studying of unusual electromagnetic field spacing and timing or frequency characteristics. Half aviation transient electromagnetic method is a commonly used aerial geophysical exploration method, with the main characteristics of Transient Electromagnetic Method, separable in time and space, easy to implement, rich amount of information collected, high precision, low cost, effective and rapid. And the system can be highly reused, mainly used for fast survey of metal ore, large areas of geological mapping, engineering geology exploration and environmental monitoring, and other fields.This thesis is based on the public welfare scientific research projects of Ministry of National Resource,"The research of half aviation transient electromagnetic exploration technology based on unmanned aerial vehicle". And thesis mainly developed its subsystem, portable airborne transient electromagnetic receiver, and focused on the key technologies of data acquisition and storage of this subsystem.The role of the receiver is to extract secondary field signals’information, which was induced by conductor underground with the first field produced by transmitter. This information reflects the different resistivity of underground conductors, so by the processing of the information, people can grasp the geological features of the target field. The secondary field information is a transient electromagnetic signal with characteristics of bigger amplitude and faster decay of early signal, but smaller amplitude and slower decay of later signal. Therefore, high performance of data acquisition system must be designed to meet these features.With these purposes, the main contents of thesis are as follows: a. The design of electromagnetic signal receiving circuits based on EM sensor. Since the half aviation transient electromagnetic exploration system has very high performance demands on EM sensor’s noise and sensitivity, the EM sensor shaping and the corresponding adaptive electric circuit research is extremely important.b. The design of signal conditioning circuits, including circuits of pre-amplification, amplification, all levels of filters, programmable-controlled instantaneous floating-point amplifier.c. The design of high precision data sampling circuits. Designed several data acquisition card to fulfill signal sampling and converting, by using4parallel24-bit high-speed and high-precision A/D converters. Proposed the thoughts of segmented and sub-frequency sampling.d. Technology of the synchronous sampling. In transient electromagnetic exploration method, it’s a very short time from the secondary field generated to disappeared, so it should be enough precise when sampling. In order to fulfill precise synchronization of the receiver and the transmitter, it is necessary to control accurately the moment of sample beginning, after the emission current was shutdown.e. Technology of data transmission and storage. High sampling rate of the receiver will generate huge amounts of data in a short time, so how to transmit them into memory quickly is a core issue to be solved. Therefore, in order to improve the performance of this system, the effective transfer and storage of huge amounts of data technologies should be well studied.In summary, the thesis focus on the research of five key data acquisition technologies of half aviation transient electromagnetic exploration system. Hardware schematics and PCB have been designed, and some parts of its function have been tested. However, the system debugging and practical application remain to be further realized.