The Design Based On Arm For High-precision Receiver Of Dual-frequency IP Instrument

Over the years, the electrical exploration theory has contributed greatly to exploring various mineral resources which are in urgent need for the development of our national economy.The dual-frequency IP method is one of the important of electrical exploration theory. The method of this new IP theory is implemented by Academician of Chinese Academy of Engineering and Professor of Central South University named He Jishan.The theory of dual-frequency IP method can simultaneously send and receive both the electric current of high-frequency and low-frequency square wave signal.The method has various merits such as greater capability of anti-jamrning, less influence from the variation of electric current, higher accuracy of exploration, faster speed of searching information, higher efficiency and so on. Since the method introduced in the1970s, Professor He successively developed a series dual-frequency IP instruments based on the theory, and these instruments were widely used in looking for metal mineral resources, groundwater exploration engineering geological exloration,and achieved good application results.In recent years, many new electronic devices and advanced instrument technology were more and more used in the geophysical instruments industry. On the current instrument development trends, this subject bases on high precision ADC, the ARM processor,virtual instrumentation, combines with the exploration theory of dual-frequency IP method, decelops a receiver of dual-frequency IP instrument which has a higher measurement accuracy, faster measurement speed.The hardware of the system includes the sensors, signal conditioning circuit(amplifier, bandpassfilter, comparator circuit, etc),ADC, power conversion circuit, the ARM microprocessor and PC host computer. Ag/AgCl electrodes are measurement electrodes MN. The electric signal is extracted from the earth by Ag/AgCl electrodes, then is inputed into signal conditioning circuit. Amplifier section in signal conditioning circuit is composed of three parts of the preamplifier circuit, low-pass filter circuit, programmable gain main amplifier. Preamplifier uses the intrumentation amplifier to difference calculate MN signal and appropriate zoom.Low-pass filter circuit is mainly used to filter out high frequency noise. The main amplifier uses programmable gain amplifier chip to achieve fourth gear gain adjustment. Bandpass filter uses a switched capacitor active filter MAX260. The chip contains two independent programmable second-order switched capacitor filter, respectively filter A. filter B. Filter A is band-pass filter for the low-frequency signal and filter B is band-pass filter for the high-frequency signal. Filter is programmed center frequency,Q value.working mode through the ARM microprocessor. The system uses a multi-range, low-power,16-bit, successive approximation ADC-MAX1303. The ADC features of simple peripheral circuitts, the chip contains its own internal clock and the reference power supply, single power supply, bipolar acquisition, multi-channel input. The main processor is produced by STMicroelectronics, and based on the Cortex-M3core. In order to facilitate system development and save time,the system uses ALIENTEK MiniSTM32developping board. The board uses STM32F103RBT6as MCU, with SD card storage, LCD display, three serial communication peripherals,to complete development needs.The system software consists of two parts, the ARM control procedures and the LabVIEW host computer program. ARM control program is written based on the RealView MDK platform and is responsible for amplification adjustment, the MAX260filter setting, analog to digital conversion, calculateing,displaying,saving,uploading the two geophysical parameters amplitude-frequency rate and apparent resistivity rate.The host computer program is written on LabVIEW virtual instrument software platform andcreate an interactive interface through the serial port to achieve instrument self-test, parameter setting, real-time data observation, data playback, and pretreatment etc function.A series of tests after the completion of the hardware design and software debugging,contain various parts of the main modules of the ciruit, establishment of the RC net to test amplitude-frequency rate and apparent resistivity rate, a series tests to the copperbox at flume laboratory. All tests achieved successful results.Finally, it is summarized all work done in this thesis,and found deficiencies in the design process, then putted forward suggestions and ideas for follow-up study.