The Design Of Signal Acquisition And Processing Board Based On AD7656

Petroleum is an important strategic material that is related to a country’s economic, military security and People’s daily life. In order to know the oil and gas situation in the exploration area, we must have to logging in the oil and gas exploration and the development process. Logging While Drilling(LWD) is a dynamic logging method that the geological parameters required during the drilling process are measured by the logging equipment installed near the drill site, the formation and wellbore information is send to the surface for processing and analysis, then it can guide the drilling azimuth. LWD can realize the synchronously implement of drilling, logging and data transmission, so it is widely used in oil drilling operations.Recently, most of the LWD data transmission are in the way of drilling fluid pressure pulse transmission. But the pulse signal detected by the pressure sensor may contain a large number of noise signal and the useful signal also will arise a significant attenuation owing to the measurement conditions and long distance transmission. In order to ensure the validity and reliability of data, it requires to preprocess the signal before the computer decoding processing. Logging signal acquisition processor can process the geological parameters in the way of isolation, filtering, amplification, A/D converter, then it transmits the processed data to the host platform decoding for drilling engineers analyzing the scene to guide the drilling work. It is an important part of the LWD operations equipment.The design of signal acquisition and processing board in this paper is based on the AD7656. It has a high resolution and good stability. It is the core of logging signal acquisition processor and connection of safety isolation circuit board and data display panel. It aims at achieve the following functions:process the signal after isolation by the safety isolation circuit board and Ⅰ/Ⅴ conversion in the way of filtering, amplification, A/D converter, under the control of the AVR, store the data in the chip SRAM, Then follow the instructions of the host machine, complete data acquisition, conversion, processing, storage and transmission via RS-232serial communication interface and PC interactive data. Firstly, this paper makes a brief overview of the significance of the background research, the system design and the main task the paper to complete. After this a description of signal acquisition processor and related equipment is given. Then it introduces the hardware of signal acquisition processor and the implementation plan of the software in detail. Including the design ideas, working principle, function realized, circuit schematic, PCB diagram, process flow diagram, physical map and so on. Finally, it gives the step and principle of system debugging, displays the debugging result, the result shows that the system can work normally, it can meet the design requirement.