The Data Acquisition System Of Three Coil Induction Logging Based On DSP

Formation resistivity is an important parameter of reservoir evaluation and reserve calculation.At present,array induction logging tool has become an important means in resistivity measurement.The paper studies the data acquisition system of a three-coil array induction logging based on DSP.The research on impact of the shield coil turns and the spacing of the measurement circuit based on designing of transmitting circuit and receiving circuit.Eventually forming an array induction tool smallest subsystem that provides the preliminary basis of designing and implementing complex array induction logging system circuit.The main research is divided into the following four parts:In the first part,the basic theory is the array induction logging.This part systematically researches the measurement principle of double-coil-system and three-coil-system in induction logging and analyzes the basis of selection to the structure parameters,advantages and working frequency of the AIT and HDIL of the array induction logging tool.In the second part,the transmitting and receiving characteristics of a three-step wave signal of multi-frequency signals are investigated in detail with LabView tool.Firstly,this part derives decomposition formula and synthesis formula of the three-step wave signal.We find the three-step signal is composited by the signal without three times harmonics.In the array induction logging tool,AIT only uses the first three of the composite signal.The synthesis and decomposition characteristics between the three-step wave signal and the harmonics waves are validated.The synthesis three-step wave characteristic of the top ten harmonics is analyzed.Finally,the methods to eliminate noise in the receiving signal are studied.A method of combination of the stack technology and Fourier transform to effectively eliminate all kinds of random noise in receiving signal is proposed.In the third part,a hardware circuit of data acquisition system including a coil system,transmitting and receiving circuits is designed.Firstly,according to the design requirements,the minimum system of induction logging data acquisition based on DSP is proposed.Then this part designs and implements the transmitting circuit program of a three-step wave with 6kHz baseband signal based on DSP chip.The F2812 DSP is the main chip to form a multi-channel data acquisition receiving circuit.Solving the amplifying and filtering problem by the signal conditioning filter circuit,it mainly uses high-precision data acquisition circuitto achieve signal acquisition.Receiving circuit includes a power supply filter circuit,amplifying circuit,etc.Finally,the circuit board is tested according to the PCB principle diagram.The fourth part is the software design of the data acquisition system,including DSP acquisition program and host computer.This part designs procedures based on DSP,and configures the system modules,including the clock,the corresponding register,external ports,the event manager and ADC acquisition module.Host computer software is developed by the VB language,which is mainly to achieve the serial communication,command and control,waveform display,data storage and data processing capabilities.After the signal is received,DSP will collect data to the host computer to display it.After completion of debugging work,the measured data results show that the design meets the requirements.The design of DSP data acquisition system can research the process of multi-frequency wave of transmitting and receiving and the mechanism of multi-frequency methods to eliminate noise.