Design Of Capacitive Differential Pressure ＆ Pressure Transmitter Based On HART Protocol

Pressure transmitter has been widely used in industrial process monitoring and control, such as process control and detection systems of oil, chemical industry, metallurgy, electric power, light industries, and so on. It is the core of on-site detection. With the rapid development of micro-computer technology and the fieldbus, Digital, intelligence and networking of pressure transmitter has become a development trend. However, early detection and control system is mainly analog instrumentation control system, it is 1 ~ 5V or 4 ~ 20mA analog signals to communicate between devices. Because of the extensive use of analog transmitter, it will take a very long time that all-digital intelligent pressure transmitter replaces analog pressure transmitter. In this process, it would be of great practical significance to develop a transmitter which is compatible with analog and digital signal.The purpose of this paper is to apply HART to design a capacitive differential pressure & pressure transmitter. Such a transmitter which is designed not only retains the traditional 4 ~ 20mA analog signal output, but also achieves two-way digital communication. The work of the hardware includes the determination of the entire system, design of each module, the connections between the modules and the selecting of the core chip. This paper writes communication protocols. The software mainly includes design of the entire software architecture and fusion information processing and other key programs. Data processing is identified a number of algorithms, the original AD data collected is processed by non-linear compensation and temperature compensation, making the data compensated has characteristics of the smallest error about linear and temperature, and the output of data with greater accuracy.In this paper, capacitive differential pressure & pressure transmitter, based on HART protocol, has virtue of digital signal and analog signals compatible, high- precision and low power consumption, etc, and has broad application prospects.