Design Of Low Power MRS Transmitter Based On Hysteresis Current Control

The method of using nuclear magnetic resonance to detect groundwater is the only method to detect groundwater directly.This method has been applied to the exploration of water storage detection in goaf,fractured water detection in Karst geomorphology,disaster water source detection,exploration of water seepage water source in open pit coal mine and so on,and the array detection method is used to improve the detection efficiency.Nuclear magnetic resonance detection of groundwater(MRS)is needed for accurate detection of near surface water sources for detecting seepage and water sources.However,the current instrument launch mode uses square wave pulse triggering to produce MRS signals.This method has long dead time and there is a certain blind area in the detection results,which will lead to inaccurate detection data of the near ground water source.In addition,the instability of the geomagnetic field gradient and the internal geomagnetic field in the mine will lead to the deviation of the Larmor frequency,and there is no corresponding solution to the deviation of the Larmor frequency by the existing instruments.Therefore,this design is aimed at the detection blind area,the detection accuracy and the Larmor frequency deviation of MRS detection device.The small power MRS transmitter is designed to solve the problem of detection blind area and detection precision b y using current hysteresis loop control mode,and the problem of detecting deviation caused by Larmor frequency deviation is solved by using sinc function envelope emission.This paper mainly designs the small power MRS transmitter by theoretical research,simulation analysis and current hysteresis control mode.The main design work includes the simulation analysis of hysteresis current control,the design of the given module of nuclear magnetic signal,the signal processing module design,the current hysteresis module design and the H bridge circuit module design.First,in the current hysteresis simulation analysis,the spectrum of the square envelope sinusoidal signal and the sinc function envelope sinusoidal signal is analyzed,and the spectrum analysis results are obtained.A spectrum analysis program is used to generate the given signal data and provide a given signal for the MATLAB/Simulink based simulation circuit.Secondly,in the design of a given signal module,the given signal is generated by STM32F103,and the signal is transmitted to the current hysteresis module after the low pass filter and the subtracer processing.The current hysteresis module uses the comparator ADCMP600 to compare the measured signal with the given signal,and through the setting of the hysteresis loop width,the measured signal is realized.The signal is followed by a given signal within the specified ring width.Finally,the H bridge is designed by using the switch frequency of the switch frequency of 4MHz,and using the H bridge driver to drive the switch device.The current sensor is used to collect the load current,and the acquisition current is transmitted to the current hysteresis module as the measured signal.This design uses the advantage of current hysteresis control to reduce the shutdown current of the load coil of the nuclear magnetic transmitter,thus reducing the energy release time of the transmitter,and can collect the determined signal when the MRS instrument is small current launching.Thus,the blind detection area and detection accuracy of MRS to earth detection are effectively solved.Using the sinc function envelope,the nuclear magnetic resonance signal has wide frequency band,which can be used to detect MRS in the case of Larmor frequency deviation.Through the introduction of the above content,the design of the nuclear magnetic resonance emission device simulation circuit analysis and hardware circuit design,and the completion of the corresponding hardware circuit debugging,based on the design of the current hysteresis loop small power launcher to realize the detection precision of nuclear magnetic instruments and detection blind area and the near ground water detection method to provide a method.It has a certain significance in the field of nuclear magnetic resonance detection.