长周期大地电磁采集系统研究

发布时间：2018-02-20 17:54

本文关键词： 深部探测大地电磁长周期斩波技术　出处：《吉林大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着我国经济的快速发展，资源和能源危机日益突出，频发的地质灾害亦严重威胁着人类生命财产安全。发展深部探测技术和进行相关勘探设备开发，将为开辟第二找矿空间、预防地质灾害以及探索地球活动规律提供技术保障，具有十分重要的现实意义和科学意义。在种类繁多的地球物理方法中，长周期、天然场的大地电磁探测能够获知地壳深部的电性信息，并且具有成本低、施工方便的优点，已经成为深部探测的重要手段，为地壳深部研究提供了重要的数据支撑。然而，我国目前还没有商品化的长周期大地电磁仪器，只能依靠进口，一定程度上限制了地球科学的发展。野外观测条件复杂，各种电磁干扰严重，对于依赖天然场的大地电磁测量来说影响较大。而长周期的大地电磁测量，要求仪器具有更强的噪声抑制能力、极低的漂移特性和较低的功耗。为了解决上述问题，本文提出了基于低功耗ARM处理器的低噪声、低漂移数据采集系统的设计。同时，为了获得更加优质、可靠的电磁观测数据，，设计了基于GPRS技术的远程监控系统，保障了数据采集过程的顺利进行。本文的主要工作如下： 1.研制了低噪声、低漂移数据采集系统。设计了基于斩波型放大器的低噪声模拟调理电路，整个信号链均采用斩波器件或低漂移器件，在获得较好噪声性能的同时，实现了极低的漂移特性；设计了基于斩波型ADC的高精度24位采集电路，在12.5Hz的采样率下，超过10000s的测量过程中，采集系统表现出微伏级别的时间漂移；采用低功耗ARM芯片作为处理器，完成数据采集，增益选择、SD卡存储、TFT液晶显示以及上位机通讯等功能；设计了基于GPS的同步采集方案，为采集数据加盖时间戳，实现分布式采集站之间的同步测量。 2.编写了基于LabVIEW的上位机控制软件。长周期仪器既可以独立工作，也可以通过串口线由上位机控制。图形界面的上位机软件方便了仪器的测试工作，便于对采集数据进一步分析，实现了仪器监控、下达指令、显示测量曲线和动态观测信号等功能。 3.设计了基于GPRS的远程监控方案。长周期仪器需要在野外长时间工作，实现采集站在无人值守情况下的正常工作十分必要，可以大大降低获取数据的人力成本。通过对电量、工作参数、同步情况的监控，可及时获悉仪器工作状态，确保采集系统稳定可靠地工作。 4.进行了系统测试和对比实验。对本文研制的系统进行了噪声测试和通道一致性测试，仪器在±5V差分输入动态范围下具有6μV左右的峰峰值噪声和1μV以内的时间漂移。与国外先进仪器LEMI-417进行了对比实验，在相同测试条件下，两套仪器获得了较为一致的磁场测量曲线，部分参数指标优于国外仪器。野外对比测试中本系统获得了相对光滑和连续的视电阻率曲线和相位曲线，验证了系统测量的准确性，表明系统工作稳定可靠，能够满足长周期大地电磁观测的要求。
[Abstract]:With the rapid development of China's economy, resources and energy crisis has become increasingly prominent, geological disasters are a serious threat to human life and property safety. The development of deep detection technology and related exploration equipment development, will open up the second prospecting space, to provide technical support for geological disaster prevention and the exploration of the earth activity pattern is very important practical significance and scientific significance.
Long period in a wide variety of geophysical methods, and detection of electrical information can be informed of the deep crust of the earth natural electromagnetic field, and has the advantages of low cost, convenient construction, has become an important means of deep exploration, provides important data for the study of the deep crust. However, at present in our country no long period magnetotelluric instrument commercialization, can only rely on imports, to some extent limit the development of earth science.
The field observation of various complex conditions, serious electromagnetic interference, the magnetotelluric measurement depends on natural field impact greatly. The long period magnetotelluric measurement instrument has stronger noise suppression ability, low drift and low power consumption. In order to solve the above problems, this paper proposes a low noise low power ARM processor based on the design of low drift data acquisition system. At the same time, in order to obtain more high-quality, reliable electromagnetic observation data, the design of the remote monitoring system based on GPRS technology, guarantee the data collection process carried out smoothly. The main work is as follows:
1. development of low noise, low drift data acquisition system is designed. The simulation circuit of low noise amplifier based on chopper, the signal chain using chopper device or low drift device, has better noise performance at the same time, the drift characteristics of extremely low; design of the chopper type ADC high precision 24 bit acquisition circuit based on the 12.5Hz sampling rate, more than 10000s measurement process, acquisition system showed time drift microvolt level; using low power ARM chip as the processor, data acquisition, gain selection, SD card storage, TFT display and PC communication function; design of synchronous acquisition scheme based on GPS. Time stamp for the collection of data, realize synchronization between distributed measurement station.
2. PC control software based on LabVIEW. Long period instrument can work independently, can also be controlled by the host computer via the serial line. PC software graphical interface convenient testing instrument, for further analysis of the collected data, the monitoring instrument, instructions, display the measured curve and dynamic observation signal.
3. the design of the remote monitoring system based on GPRS. The instrument needs long period in the field work for a long time, the normal work of collecting station in unattended condition is necessary, can greatly reduce the manpower cost. By obtaining data on electricity, monitoring parameters, synchronization, can be timely informed of the state of the instrument, to ensure stability the reliable work of acquisition system.
4. a system test and contrast experiment. The system proposed in this paper for the noise test and channel conformance testing instrument with time difference drift within peak noise about 6 V and 1 V input dynamic range is within 5V. With foreign advanced instrument LEMI-417 were compared in the experiment. Under the same testing conditions, two sets of instrument measuring curve of the magnetic field is more consistent, some parameters than foreign instrument. The system was relatively smooth and continuous curve of apparent resistivity and phase curves of field contrast test, verify the accuracy of the measurement system, show that the system is stable and reliable, can meet the requirements of long period magnetotelluric observation.

【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P631.325

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