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核磁共振(NMR)测井仪以CPMG脉冲序列为测量基础,按照CPMG脉冲序列的时序要求完成大功率射频脉冲的发射和微弱回波信号的接收,在脉冲发射完成后快速泄放天线中储存的能量.该文介绍一种基于现场可编程门阵列(FPGA)的NMR测井仪控制逻辑和典型脉冲序列,详细说明在CPMG脉冲序列下FPGA的工作时序和流程;讨论NMR测井仪发射电路、Q-转换电路和隔离电路的控制原理和时序要求,给出各电路的控制逻辑仿真结果;最后,利用所设计的控制逻辑和自制NMR测井仪探头,在实验室条件下对水溶液进行了测量,得到满意的结果.
The nuclear magnetic resonance (NMR) logging tool based on the CPMG pulse sequence is used to complete the transmission of high-power RF pulses and the reception of weak echo signals according to the timing requirements of the CPMG pulse sequence. The NMR pulse log Energy.This paper introduces a NMR logging tool control logic and typical pulse sequence based on field programmable gate array (FPGA), and details the working sequence and flow of FPGA under the CPMG pulse sequence; discusses the NMR logging transmit circuit, Q-switching circuit and isolation circuit control theory and timing requirements, and gives the control logic simulation results of each circuit; Finally, the use of the design of the control logic and homemade NMR logging instrument probe, the aqueous solution was measured under laboratory conditions , Get satisfactory results.