Design Of Logging Data Acquisition System Based On BF537for Through Casing Formation Resistivity

This paper introduces the design plan and implementation of the logging data acquisition system of Through Casing Formation Resistivity. Based on the current research development situation and achievements of the Through Casing Formation Resistivity logging technology in home and abroad, the general principle of this technology is being introduced in this paper, the apparent formation resistivity calculation formula of the Russian Through Casing Formation Resistivity logging instrument--ECOS31-7and Schlumberger’s CHFR is derived, and also the driving signal feature and response signal magnitude are analyzed as well as the data acquisition system of Through Casing Formation Resistivity is designed on this basis. According to the general requirements of Through Casing Formation Resistivity logging instruments, the component of the data acquisition system is analyzed and satisfactory circuits are designed.In the hardware circuit part of the system, the amplifier circuit which based on low noise instrument operational amplifier AD620is designed by analyzing the noise source and eliminating methods, the interferent source and suppression measure of the amplifier circuit. In the meantime, based on combining modular design idea, signal acquisition circuit with CAN bus data transmission module is designed based on high speed DSP chip BF537and high resolution AD converter ADS1274.In the software part of the system, through the analysis of ADS1274data transmission protocol, data reading measure based on DMA technology is designed, and the concrete realization process is presented. In order to increase the signal to noise ratio of the system, sample data is processed with median average filter measure. Simultaneously and emphatically, the over sampling technology and median average filter measure used in the system realization process are theoretically analyzed. And the concrete realization measure is provided. The experimental result shows, the measure accuracy of the whole system generally meet the designing requirements.