Multi-channel Data Acquisition And Optical Fiber Communication System

Nowadays,data acquisition system is applied in comprehensive domains with the development of sensor techniques,fiber communication and information processing techniques.This thesis studied the application of data acquisition system in the field of online monitoring of the large capacitance electric apparatus(LCEA).In this thesis, the importance of monitoring on some eigenvalues,especially the dielectric loss factor is approved via brief introduction of the concept and significance of the online monitoring system of LCEA.After that,we proposed and implemented a distributed data acquisition system for the online monitoring of LCEA.The combination of Filed-Bus and Fiber Communication techniques,Digital Signal Processing and Computer techniques was used in implementing this system and achieving the goal of accurately monitoring and analyzing the insulated status of multiple LCEAs.The outline of this thesis:(1) Based on introduction and comparison of several dielectric loss factor monitoring methods,a discrete Fourier transformation method with dynamic sample rate was proposed and illustrate.(2) Introduced two common structures of online monitoring system for LCEA.Based on the analysis and comparison,a distributed data acquisition system combined with fiber communication system was proposed and implemented.(3) Designed and implemented the data acquisition unit.The data acquisition unit collects signals from different sensors and doing a synchronized sampling and processing on the multiple signals under the control of the core data processing circuit.(4) Designed a multi-layer communication protocol which is based on RS-485 and constructed a master-slaves filed communication net with this protocol.Both the circuit design and the details of the communication protocol were thoroughly discussed in the thesis.(5) Designed graphical user management software to control and manage the work of the online monitoring system.The software also provides the user with viewing, modifying and analyzing the monitored data.(6) Installed the monitoring system on the field and get a large amount of real data. The system got a good remark from the user and related experts.We also investigated into these data in the thesis.