The Design And Implementation Of The Meterage, Management, And Remote Supervising System For Natural Gas

This master thesis aims at developing a natural gas meterage, management and remote monitoring system with distributed hierarchy, which is based on the RS-485 bus and the Modbus Plus network in PC in the field. The system, which is oriented to the application to the stations of natural gas, is designed to meet data acquisition, meterage, management and remote monitoring in the supervising center. The system has the following remarkable features: real time response, high compatibility, high expandability, strong anti-interference, high precision, high reliability and friendly man-machine interface etc.Based on the requirement analysis, the overall design and the physical structure of the subsystem in the field are carried out firstly, and the design requirement of the software system is given. The paper analyses the network form in the field, and the design and implementation of the software. For software design, the communication module, flux measuring module, and database module are presented, and some communication interface such as RS232, RS485, Modbus is considered in the physical structure design. The emphasis is placed on the communication protocols of the subsystem in the field. Secondly, the thesis deals with the interference problem and the anti-interference techniques in the field subsystem. At the same time, the remote communication forms and implementation are presented between the subsystem and the supervising center. Thirdly, the detailed design and implementation of the system in the field in the visual basic integrated development environment are introduced. Here, attention is especially paid to the communication design, the communication design and implementation based on the RS-485 bus and the Modbus communication protocol. Finally, a conclusion is drawn from the paper and the technique of virtual instrument, the front technique in the field of industrial control, is mentioned.