| Transmittet and receiver of the multi-frequency array induction logging signal are the core parts in the tool design. This thesis studies both transmitting and receiving methods of multiple frequencies of the array induction logging tool. At first transmittet and receiver of the multi-frequency array induction logging signal are simulated by the Lab VIEW software and the feasibility is tested. Then the hardware is designed and the experiment device of multi-frequency signal’s transmitter and receiver is developed. The specific content and results mainly include the following aspects:The first part mainly studies the transmittet and receiver mechanism of the multi-frequency array induction logging signal, Fourier expansion formula of a square wave signal is derived. It proves that the decomposition of square wave is odd harmonic waves and synthesis of odd harmonic waves is a square wave. Then transmitting and receiving properties of eight arrays multi-frequency without noise are simulated by the Lab VIEW software. The results show that the synthesis transmitting signal of eight harmonic frequencies approximates a square wave, while the receiving signal is not square, but it has the characteristics which can present the square wave information. Finaly, the characteristics of transmitting and receiving with noise is stdudies. The simulation result shows that the stack technology combined with Fourier transform can eliminate effectively all kinds of random noises in receiving signal. These results are the foundation to design the multi-frequency array induction logging signal tool’The second part designs the hardware circuit, including transmittetting, coil system and receiving circuit three parts. A square wave with 10 KHz harmonic frequency is generated by a high and low level circut produced by DSP processor and a program which can make the duty ratio of 50% and frequency PWM pulse width modulation waveform. Transmitter circuit consists of DSP chip and its peripheral circuit. A typical three-coil system which can be used in the lab is made. A multi-channel data acquisition circuit based on the 2812 DSP is built. The problem of signal amplification filter can be solved by the regulating filter circuit. Data acquisition function is realized by a high accuracy collection circuit The recerver circut includes the power supply filter circuit, signal conditioning circuit, peripheral circuit, serial interface circuit, external memory circuit. Finally the test circuit board is completed according to the principle diagram of the PCB.The third part finishes the software design of the experiment devic of array induction logging, including the DSP acquisition program, correction method, the design of upper machine, etc. Design the DSP acquisition software. Realize the module system, including time clock, register outside port, event manager and ADC acquisition. Choose the least square method of correction method to improve the acquisition precision. Develop the upper machine based on VB language development. It mainly realizes the serial port communication, command and control, and waveform display and data storage and data processing, and other functions, the post processing analysis of the data is very convenient. DSP will collect the received signal data to PC interface display.The system debugging work is done, the measured result shows that the design of this device meets the requirements. The developed transmittet and receiver experiment device of the multi-frequency array induction logging signal tool can be used to study the multi-frequency signal transmitting and receiving process and the mechanism of the multi-frequency method to eliminate the measurement noise. |
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