Magnetid Circuit Simulation And Circuit Designin Of The NMR Logging

NMR logging tools are based on the oil well reservoir fluid NMR responsecharacteristics of the large differences in the design of a detection instrument, takeadvantage of this difference distinguish types of hydrocarbons, can also quantitativecalculation of their volume. The subject by the relationship between the RF field and thestatic magnetic field of the NMR logging on and the interaction of the fluid in the reservoir,which is a static magnetic field the polarization of the fluid in the reservoir and the fluidproton RF field to generate energy released through the release of energy conversion of theelectrical signal into the signal reception circuit, the signal to the corresponding processingis displayed through the PC corresponding to the characteristic information. The subjectsimple circuit design to meet the environmental requirements of the well volume hasimportant reference value for the domestic NMR logging hardware circuit and softwaredesign.The paper first introduces the basic principles of NMR logging ANSYS simulationanalysis of the magnetic circuit of the permanent magnet in the logging tool to understandthe distribution of the magnetic induction around the borehole, in order to know to detectdifferent position should correspond with different the frequency of the signal excitation.Secondly discusses the design principles of the hardware circuit, chip select, parameterselection and some experimental results, given the measured waveform of the circuit. Thesystem hardware circuit includes experimental USB serial communication circuit, thesignal excitation source circuit, shaping circuit, FET H-bridge driver circuits, switchingcircuits, MCU control circuit and peripheral interface circuit. The hardware circuitmicrocontroller to control the AD5930to generate frequency tunable, wave first fewadjustable repeat cycle adjustable pulse sine wave, comparator then shaped into a squarewave, the subject also discusses another use phase-locked loop signal source to produce amethod, respectively of these two signal sources through MOSFET driver drives FETconstituting the H-bridge driver circuit, the series resonant circuit is designed in theH-bridge circuit, the inductance of the coil with a capacitor in series, adjusted Larmor resonant frequency by adjusting the capacitance value, thereby regulating the amplitude ofthe excitation voltage of both ends of the coil probe, while an increase in the probe portionof a damping resistor, the fast decay of the excitation signal, and prevent tailing. Subjectsoftware parts including microprocessor control program compiled using keil C and C#prepared by the PC control interface.From the hardware and software aspects of the design of a simple logging circuit, theexcitation signal is applied in the reservoir fluid and produces a measurement signal,further underground test the adequacy of the experimental data.