Application of CS3301 to the long-period MT instrument

作者：Gong Xiu Gang^*; Wei Wen Bo; Jin Sheng; Ye Gao Feng; Chen Kai

来源：Chinese Journal of Geophysics, 2012, 55(12): 4051-4057.

DOI：10.6038/j.issn.0001-5733.2012.12.017

• Magnetotelluric sounding
• Weak signal detection
• Data Acquisition
• CS3301

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 X 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 X 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.

• 出版日期2012-12
• 单位中国地质大学（北京）; 山东理工大学