Research And Design Of Automonitoring System Of Multi-Pressure

Pressure measurements are widely applied to liquids and gases in production, so that their pressurelevel can be acquired accurately and timely for production management, quality control and safety.According to the practical situation in production, a pressure monitoring system which consists of acomputer and multi-pressure sensors distributed at many points is developed in this dissertation. Thebasic principle of the system and its structure and constitution are introduced, and the function of itssoftware is described.The hardware of the system includes pressure sensors, temperature sensors, a signal processing andtransmission circuit, a multiplexer circuit, a multifunction A/D data sampling card and a computer. In thesystem, diffusion silicon piezoresistance sensors are adopted as pressure transducers. After signalmodulation by the signal processing circuit and channel transformation by the multiplexer circuit,pressure signals from the sensors are sampled by the A/D sampling card and transmitted to the computerthrough its ISA bus. Then by data transmission through the Internet, these sampled pressure data areshared by other computers in a long distance.The software of the system is developed on a graphics language platform LabVIEW in a Windowssurrounding. The main functions of the software include a main interface, data sampling,anti-disturbance operation and digital filtering, result and real-time waveform display, calibration ofpressure parameters, alarming by means of sound and light, and data store and transmission throughinternet. Due to the abundant functions of LabVIEW and adoption of a modularized design, the softwarehas a clear structure and is easy to be debugged, revised and transplanted, which help improve theefficiency for system development greatly.To improve the system accuracy, temperature drift characteristic of the sensors is analyzedand temperature compensation by means of hardware and software are proposed.It was proved by experimental test that the resolution of the system is better than 0.0075Mpa andthe total measurement error is less than 0.2%. The system has friendly man-machine interface, highreliability and stability,and high property-price rate, and so has good prospect for wide application.