Research And Design Of Encoder/Decoder In Petroleum Seismography Technology

As the rapid development of the world industry, the consumption of the resource is increasing sharply which results the worldwide resource crisis becomes more and more serious .In this situation, all countries intensify their work on prospecting petroleum.Because seismography has high degree of accuracy and resolving power, it is widely used in prospecting petroleum. In seismography, seismic waves which was made by an artificial epicentre travel in stratum. Through analyzing a great deal of echo, which arrives the earth's surface at different time, the seismography can prospect the distribution of petroleum. In this method, the key technology is the precise synchronization between the time break of detonate detonator and the start time of sampling and recording echo data. The apparatus calls exploder or Encoder/Decoder. Encoder/Decoder is very important in seismographic apparatus.This dissertation mainly introduces the status quo and the principle of Encoder/Decoder, the key technology and the difficulty in Encoder/Decoder especially. The scheme of the apparatus, the electro circuit design, and the software design is introduced in the dissertation subsequently. And the result of Experiment on Encoder/Decoder is introduced at the end of the dissertation.One Encoder/Decoder has the function of encoder, decoder and system management mode. The synchronization error between the signal TB and the signal FIRE is less than ±20μs. The detonation voltage is adjustable between 300 and 600 voltage. And the distance of communication between encoder and decoder is farther than 8km. It can measure physical parameter real timely, and has the function of self-examination. The level of this apparatus is no less than the up-to-date production produced overseas.The Encoder/Decoder uses two key technology: the high-speed andhigh-powered microprocessor--Atmegal28 and complex programmable logicdevice technology--EP1K50TI144-3. Atmegal28 is mainly used to achieve thefunction of macroscopic management and controlling of the system. The digital logic and scheduling in EP1K50TI144-3 is inclusive of Atmega128 bus-mastering, code and decode in communication, detonation control, interrupt management, and the joint logic for keyboard, LCD, and so on. In the circuit system, it also uses A/D and D/Atechnology, power management and signal isolation technology, programmable amplify technology, wireless communication technology and the control technology of programmable charge and discharge. The wireless communication adopts Manchester code and decode. The precise synchronization is accomplished by rational compartmentalizing the task, which is achieved by software and hardware in according of the characteristic of MCU and CPLD.MCU accomplishes the function of macroscopic management and controlling of the system by C programme in Atmega128. And the digital logic and scheduling in CPLD, the high-speed and complex logic's parallel disposal, the high-speed and exact data processing is achieved by VHDL programme and graphics.Four keys is used in the apparatus. And LCD is used to display multilevel menu and parameter. Operator can use it easily and conveniently.