| CS3301在长周期大地电磁测深仪中的应用研究 |
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| 引用本文： | 巩秀钢,魏文博,金胜,叶高峰,陈凯.CS3301在长周期大地电磁测深仪中的应用研究[J].地球物理学报,2012,55(12):4051-4057. |
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| 作者姓名： | 巩秀钢 魏文博 金胜 叶高峰 陈凯 |
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| 作者单位： | 1. 中国地质大学(北京)地球物理与信息技术学院,北京 100083;
2. 山东理工大学计算机学院,山东淄博 255049 |
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| 基金项目： | 国家专项"深部探测技术与实验研究"(SinoProbe-01 |
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| 摘 要： | 大地电磁测深是研究地壳和上地幔构造的一种重要的地球物理探测方法,当前国家正在实施深部探测专项SinoProbe等项目,故需要借助于长周期大地电磁测深仪器.我国没有自己生产的长周期大地电磁测深仪器,只能依靠从乌克兰进口的LEMI-417进行深部探测.在LEMI-417使用中,我们从该仪器提供的数据文件Final.asc中发现它的电场信号测量分辨率为0.01 mV/km,磁场信号测量分辨率为0.01 nT,相对较低,此外,该仪器在无GPS信号时会出现记录紊乱等现象,故需要设计适合课题组需要的长周期大地电磁测深仪器.由于大地电磁测深仪器需要采集的电场、磁场信号为微弱信号,容易淹没于噪声之中,故选用了低噪声、极小总谐波失真率的CS3301作为运算放大器.CS3301提供了4种可选择的信号输入模式和7种可选增益,经分析与测试,测量电场信号时,CS3301设置为输入模式1及×64增益,当极距100 M时,测量精度可达0.001 mV/km,高于LEMI-417的0.01 mV/km;测量磁场信号时,将反馈理论用于测量电路,CS3301设置为输入模式3及×64增益,只对信号的可变部分进行放大,精度可达0.006 nT,高于LEMI-417的0.01 nT.该系统在华南的9005、1005等多个测点以及东北的1600、5105等多个测点进行了测试,并与LEMI-417进行了对比试验,测量结果表明它们的时间序列曲线比较一致,数据处理后,在同一测点得到的大地电磁测深曲线也较一致,说明设计的仪器达到了预期目标.
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| 关 键 词： | 大地电磁测深 微弱信号检测 数据采集 CS3301 |
| 收稿时间： | 2012-05-08 |
Application of CS3301 to the long-period MT instrument |
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| GONG Xiu-Gang
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WEI Wen-Bo
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JIN Sheng
,
YE Gao-Feng
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CHEN Kai.Application of CS3301 to the long-period MT instrument[J].Chinese Journal of Geophysics,2012,55(12):4051-4057. |
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| Authors: | GONG Xiu-Gang WEI Wen-Bo JIN Sheng YE Gao-Feng CHEN Kai |
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| Institution: | 1. School of Geophysics and Information Technology, China University of Geosciences (Beijing),Beijing 100083,China;
2. College of Computer Science and Technology, Shandong University of Technology,Zibo Shandong 255049,China |
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| Abstract: | Magnetotelluric (MT) sounding is an important geophysical method to probe crust and upper mantle structure. The long-period MT instrument is essential during the project "Deep Exploration Technology and Experimentation (SinoProbe)" in China. However, China cannot produce the long-period MT instrument by itself now and only relies on LEMI-417 imported from Ukraine. When using this instrument, we find the resolution of electric meter is 0.01 mV/km and the resolution of magnetic field signal is 0.01nT through its data file Final.asc, which shows its accuracy is low compared with other MT instruments. And the LEMI-417 did not work normally without GPS signal when data acquisition of LEMI-417 was used by our group team. So it is necessary to develop a set of long-period MT instrument which meets the need of our project. As MT signals, include electric field signal and magnetic field signal, are weak and easy to be embedded in noise, they need to be amplified. Thus, the amplifier CS3301 with outstanding amplifier noise performance and extremely good distortion performance is selected. The CS3301 provides four input choices and seven gain selections, which are made through using the MUX and GAIN pins. After analysis and testing, CS3301 is set under gain ×64 and input mode 2 in the electric signal acquisition circuit. In this case, if the polar distance exceeds 100 meter, the resolution of electric meter is 0.001 mV/km. It is set under Gain ×64 and input mode 3 in the magnetic signal acquisition circuit, which uses the feedback method to deduct the constant signal and makes the amplifier only amplifies the variable signal. And in this case, the resolution of magnetic field signal is 0.006 nT. As comparison tests, the instrument with CS3301 and LEMI-417 were used to collect MT data at several measuring points at the same time, such as measuring point 9005 in South China and measuring point 1600 in Northeast China. The results show that their time series curves are consistent and the MT sounding curves after data processing are consistent too. |
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| Keywords: | Magnetotelluric sounding Weak signal detection Data Acquisition CS3301 |
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