A Monocable Telemetry System Design

Based on practical need, A monocable telemetry system,which serves as down-hole data acquisition & transmission in computerized production logging system(CPLS), has been developed.lt has been proved that this system is feasible and can be put into use.The system is advanced ,it greatly improves domestic production logging instrument and will spread widely as replacement for imported products.The paper involves:The necessity to develop a monocable telemetry system,its important use in CPLS,and the advance of data transmission technique in production logging instrument are introduced. The theoretical and financial significance to design a monocable telemetry system are adressed.According to electric&magnetic and circuit analysis theory,monocable transmission characteristics is analysed.On this basis,the transmission characteristics of the monocable in use is analysed and caculated.Monocable is thousands meter long,electrical signal transmission along monocable shows long line transmission characteristics.Monocable characteristics analysis is helpful to monocable telemetry system design,such as data transmission rate selection,circuit design,etc.Based on the above analysis results,the system design is finished.The system design principal is detailed.The system architecture and data transmission proctocal are discussed.In order to transmit multi-channel data simutaneously on the monacable,TDM(Time Division Multiplexing) technique is adoped in the system design.A special code is designed for data transmission on the tool-bus, so that the too-bus can both supply power and transmit data.Following the system design principal,hardware and software design of the monocable telemetry system are accomplished. Circuit diagrams and software flowcharts are gived.Hardware anti-interference and reliability design,and software anti-interference design method are adressed.Computer parallel technique is employed in order that the telemetry system can send data up to surface equipment while receiving data from down-hole tools.Finally,test results and future plan are presented.