【作者】 王笑；

【导师】 陈仁文；

【作者基本信息】 南京航空航天大学 ， 测试计量技术及仪器， 2007， 硕士

【摘要】 针对当前各个领域中仪器的智能化、信息化、网络化的发展趋势,传统的流量计和通用的流量积算仪也力求提高精度和使用范围,以便实现流量测量远程监控和信息共享。传统的流量计大都采用HART、CAN、RS485等进行组网,由于几种总线各有特点但互不兼容,不能统一组态,给用户带来了不便;而且在传输距离、扩展性、通信速率等方面也受到很大的限制。随着以太网技术的发展,本文提出了一种基于TCP/IP传输协议的网络化流量测量方案,即采用标准的网络协议,将流量测量和网络技术有机的结合起来,使客户机实现对现场流量测量的远程控制和数据处理。本系统以单片机为控制核心,采用了模块化结构。在流量测量模块中,首先选取相应的传感器设计测量电路,获取积算所需的差压信号以及补偿所需的绝压和温度信号,再通过单片机控制A/D模数转换进行信号的采集以及软件补偿、积算和显示;单片机还可以提供积算算法在线更新的功能;在网络传输模块中,通过单片机控制网络协议栈芯片的运作,并通过网络接口芯片与以太网进行连接。单片机处于不停的监听端口等待远程连接的状态,当远程客户机访问该系统时,单片机根据远程客户机不同的指令,将流量传输给远程客户机,以供远程客户机进行数据处理和监视。该系统实质是使流量计本身实现TCP/IP网络通信协议,将流量计作为网络节点直接与计算机网络通信,大大提高了系统的数据传输速度、传输距离以及测量精度。通过网络,用户能够远程监测或控制过程和实验数据;通过网络,一个用户还可以远程监控多个测量过程,而多个用户也可以同时对同一过程进行监控,具有更大的实用价值。更多还原

【Abstract】 In the trend of intellectualization, informationalization and networklization of the instruments in various fields, the traditional flowmeter and current flow totalizer are required to improve the precision and enlarge using area which can achieve the goal of remote measurement and information sharing.Such buses as HART, CAN and RS485 are mostly adopted to form a measurement network in the traditional flowmeters. But it has some disadvantages that they employ different protocols such that they can’t be configured uniformly. Furthermore, their transmission distance, expansibility and transmission rate etc. are limited. With the development of Ethernet, a networked flow measurement system based on TCP/IP protocol is present in the paper. This is to enable a client, by a standard network protocol, to have online flow measurement and the capabilities of data monitoring and control with the combined technologies of flow totalizing and network.The system is of modular structure and uses a single chip microcomputer as its controller. For the flow measurement, sensors should be chosen at first, and then the transduction circuits are designed to transform the differential pressure which is the main variable, the absolute pressure and the temperature into the voltage signals, after that, the voltage signals are converted to digital signals by the A/D convertors under the control of the MCU. The MCU also processes these digital signals and cumulate the flow quantities, makes software compensation and LCD display. Besides, the MCU can update the algorithms of data processing. For network data transmission, the MCU controls the operation of the hardware protocol stack chip and connect to Ethernet with an Ethernet PHY chip. The MCU monitors the port and waits for connection with the client, and will transmit required data to the client according to the client instructions when the connection succeeds.The goal of the system is to make an intelligent flowmeter as a network node to communicate with a computer network with TCP/IP protocol. The transmission rate, transmission distance and measuring precision have been improved in this schem. The client can monitor and control the whole process and data; it is possible that one client can monitor multiple processes and different clients can monitor the same process at the same time. Therefore it is practical.更多还原