Based On Hart Protocol Intelligent Pressure Transmitter, Research And Development

The rapid development of information technologies have made instruments, such as sensors and transmitters, develop in higher precision and reliability, and also in automation, multi-function and intelligence. The fieldbus is a technique, which could take a great role and therefore a rapid development in the revolution of industrial measurements and automatic systems. Smart transmitter is a typical intelligent instrument in which integrated with the sensor and the communication system. Compared to general the conventional analogue transmitter, the intelligent transmitter has not only higher precision, better reliability and stability, but also the real-time characteristics and intelligence. It can be widely applied in scientific measurements and industrial automations, and so has the paramount importance for researching and developing.Fieldbus is hot topic in automatic detection field nowadays, which is an opening, digital and multidrop communication control network of low layer. The development of full-digital system in fieldbus is a general trend. However, 4~20mA analog signal instruments also have a large application in industry, the HART communication protocol —a transitional protocol during transition from analog system to digital system—emerges as the times require. Based on Bell 202 communication standards, HART protocols transfer data with different frequency signals and plus with 4~20mA of analog signals.Being based upon HART protocol, this paper combines the MCU and sensor to an intelligent transmitter. Firstly, the detailed the hardware analysis and designs are introduced, including the single-chip microcomputer, the sensor module, the communications module and A/D , D/A module; Then, the structures of the software are analyzed and designed. Furthermore, the data fusion is proposed to mitigate the crosstalks between different measured parameters; After that, the systematic program approaches for the field communication and the specification design are discussed. Finally, the problems and experiences met in developing the software and hardware of the system are summarized in the last part of the paper.