The Research Of A Venturi Flow Meter Based On Field Bus

Field Bus is double-direction, serial and multi-node digital communication technology that applied between local device/instrument and servomechanism system in area of process. Its node consists of distributed, digital and smart device to test and control and connected by bus to realize exchange of information, so that share information in different net and local device. PROFIBUS is an international and open field bus standard independent with manufacturer. It is widely applied to automation of manufacturing, industrial process and automation on building, transportation, electric power and building material. In automation of cement industry, PROFIBUS has successfully adapted. So it requests total instrument to hold communication ability of PROFIBUS. So we shall face to new task that rebuild and research instrument to adapt to PROFIBUS standard. Venturi Flowmeter is instrument to measure flow of gas usually used in cement industry. However traditional Venturi Flowmeter has not function of PROFIBUS communication. So it hardly satisfies modern requirement of Totally Integrated Automation.This design used the conventional Venturi Flowmeter which is used to measure the second wind flow to make it can have the ability of communicate PROFIBUS-DP, meanwhile do not reduce precision. Then it has become a smart node of the PROFIBUS control system, satisfies modern requirement of cement industry control.This paper introduces principle of Wenturi Flowmeter in detail and finished design of structure; meanwhile have an in-depth study to PROFIBUS Field Bus technology. This paper has designed interface of Wenturi Flowmeter of PROFIBUS-DP, has finished design of circuit of drive and selection of DP interface, and has analysed arithmetic of DP sub-station and has programed program.Hardware of interface adapt ASIC chip SPC3 made in Siemens, 8032 singlechip, AD7574 and DAC0832. In design of circuit of hardware, designed respective circuit of A/D and D/A. In design of function of software, because complicated task is assigned to host-station, ensure real-time and reliability of DP sub-station. In design of software, we adopted method of program of structure, design respective module of program for communication of sub-station and channel of output and input. DP sub-station adopted control arithmetic of PID, could finish closed loop control to simple and independent object by self.