Research On Intelligent Differential Pressure Transmitter Based On Hart Protocol

With the development of the computer technology, instrument and meter have the trend to automation and multi-function. And the fast development of the fieldbus requires that a transmitter or a sensor should have good reliability and higher precision. With the development of the modern industry, the automation system gets huger and huger and more and more complex and its aim has changed from the past at stability to today at large-scale assemble and optimal control. The application in more fields also needs a better transmitter. So many overseas corporations have produced new intelligent transmitters. But in our country only a few corporations have produced them, so the research and exploitation on intelligent transmitters have an important sense of theory and practicality.In the fields of petroleum industry,chemical industry,metallurgic industry,electrical industry,pharmacy, the measure of differential pressure is universal and a pressure transmitter is one of the most widely applied meters. A pressure transmitters is a locale meter applied to measure the flow, differential pressure, pressure, liquid level, density and so on, of the liquid in procedure, which is an important component of automated process detection and control system in sequential procedure. It can convert measured technical parameters,such as pressure, to corresponding standard electric signals, and then send the signals to other units to accomplish the automatic detection or adjustment of the parameters.During the transient period when the standard of Fieldbus has not be unified completely, how to meet the market's huge needs for intelligent local meter? Now the Highway Addressable Remote Transducer (abbreviated to HART) protocol products can do this. Because on one hand, it can keep the application of the analogue signals of 4 to 20mA insure that the former investment can take effect sequentially,on the other hand, it makes users contact digital signals gradually so that the whole digital system can come into markets overall.In this paper, firstly, the HART protocol and its application in local meters is discussed. Secondly, the development and the theory of operation of an intelligent pressure transmitter are analyzed and the error correct and the power consumption of it are presented and solved. Thirdly, the data interfusion technology and automatic test is presented. And then, the theories of operation of the sensor and the hardware, the function descriptions of the software and the function and capability criterions of acapacitive intelligent differential pressure transmitter are presented. At last, the total scheme of the software design is put forward.A series of intelligent differential pressure transmitters marked HBCC/HBYC are exploited with a lot of new techniques. They have better capabilities and more functions than general analogue transmitters. With the development of our technique, more consumers will care for this new type of transmitter.