Research and Experimental Study on Receiver of Deep Three-dimensional High-density Resistivity Method

Abstract: The content of this paper is part of "Old Mine Disaster Prevention and the Detection of key technologies and equipment".the project supported by the "Eleventh Five-Year" national scientific and technological projects. The high-density resistivity method is employed as the detection method in this project. This paper is concentrated on the design of acquisition device applied the high-density resistivity method. The experimental result was analyzed and the device was improved in the performance and operation on the basis of the filed experiment. The acquisition devices including the control part of PC software, the acquisition part of the signal and switching part of electrodes. Some field experiments include Shao guo town Chang chun city logging experiments and Tao chong iron gob Anhui province experiment The control of emission current, relay communications transmission and electrode power station were improved.The main controller of the receiving device adopted MSP430 MCU, using its serial port to communicate with PS. After Emission current Injecting the earth , through the RS-485 bus the microcontroller controls electrode combinations of switching devices, After receiving electrode collected signal conditioning part of the pre-acquisition card after the USB-7889 is converted to digital. In the VB programming environment, the preparation of acquisition card control program, combined with VB and EXCEL nested call to collect the data stored in the EXCEL table. Acquisition part is an important part of the equipment. Its performance indicators will directly affect the detect effects. The high-density resistivity method requests electrical collection system with low noise, small size, low power consumption, light weight, suitable for field operation.After the development of the device, a number of tests were done to verify its functionality and reliability including two large-scale field tests conducted in Jilin and Anhui Province. Two tests achieved the device‚Äôs functional testing and have good results. Log in Shao guo town experiment, after inversion compared with the data mapping and drilling results are consistent; in Tao chong gob experiment can detect the approximate gob distribution. Some deficiencies were found in the tests including the communication signal stability, field wiring, battery monitor and control of the emission current. Improved program was proposed to resolve those issues.Taking the Complex environment of the field experiment and facility for users into account, PC104 Industrial Computer was used to replace the laptop computer in the system. IPC has lots of the advantages such as a small volume, simple operation and a single 5V power supply. According to the performance requirements of device, PC104-1641CLDNA (B) module produced by Beijing EVOC Intelligent Technology Co., ltd. was used. Instrument control interface is designed in Visual Basic language programming environment. The emission current should be known for earth resistivity inversion. Therefore, it must to be kept constant to get a more accurate measurement in the filed test. And the real-time monitoring circuit for the emission current was added in the later improvement of the device. This will realized the closed-loop control of the current to maintain it constant. With current CT acquisition of emission current, collected by the AD 89C51 MCU, MCU according to the collected current value and the change in control digital potentiometer DS1867 to change the switch voltage and current, the end to maintain the stability of emission current.The design of signal communication relay transmission was also puts forward in the later improvement of the device. RS-485 relay communication mode could greatly improve the capability of signal transmission,and can simplify operational processes of the wiring. Program using relay communication signals in the test line up only one unit of distance measurement line length (100 meters), this can greatly improve the reliability of signal transmission. System uses the relay transmission, the electrode measured line coding method also be simplified. In the early instruments, the only electrode code (1 ~ 150), followed by relay stations encoded into 1 to 5, a total of 30 units of measurement lines are the same, so when in the field wiring becomes simple and efficient. The design of the power station was proposed to supply power for electrode line. A power station was installed in both end of the electrode line, while the PC controlled the power supply of whole the line. This can avoid the waste electricit caused by successive power mode. In addition the power stations add the function of measuring the battery voltage. So the PC can realize real-time monitoring of battery volume and display it.The section about the test includes the test of performance parameters and functional test. The Performance indicators contains amplifier noise of analog signal conditioning part, the magnification amount,the performance of the notch filter and AD capture card. And functional testing contains the test of relay communication signal transmission, test of power station, and controlling of current collection. RS-485 bus was used to the control electrode switching device and the test of earth resistance in the part of relay transmission test. Finally the process and results of two experiments were introduced in details, and the performance parameters of the device were verified.The thesis introduced the the design of acquisition device applied the high-density resistivity method, the filed experiment and improvement of Acquisition Device. And the further suggestions for improvement were given in the final…
Key words: high-density resistivity method; closed-loop control; relay stations; power station; field experiment

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