| In the industrial process automatic control system, transmitter can measurephysical parameters such as temperature, pressure, liquid level, flow and so on, andthen transform them into a unified signal according to certain standard, so it is one ofimportant elements in automatic control system.The automation instrument device use4~20mA standard analog current forpower supply and signal transmission. In order that instrument device can calibrateon-line and diagnose fault, the microprocessor technology and HART field bustechnology is used. The technology can detect instrment with a dedicated terminal bythe point to point4~20mA signal line, and solves the requirement of set of fieldinstruments and diagnostic. But because the conventional HART intelligent transmitterdetection signal transmit mainly in analog signal, and the digital signal transmissionrate is low, so it can not satisfy the real-time requirement, only use it to set anddiagnose fault. At the same time, for managing the instrument, pepole must connectthe terminal to each detection instrumentation point to point. It need to invest morehuman resources for large production systems, and low efficiency.In this paper, an improved intelligent transmitter based on HART protocol isproposed through analysis of embedded Linux system and the application of wirelesscommunication technology in remote industrial control,and summary design principleof intelligent transducer at home and abroad. the embedded system is chosed toimprove the instrument design in this project, WIFI technology is used for digitalinformation transmission through connecting the wireless router to the LAN. With thisdesign, clents can access to the instrument directly by computer. the paper deeplyanalyzes the HART protocol standard specification of every layer, and the advantagesand disadvantages of conventional HART intelligent transmitter, introduce theimproved intelligent transducer design principle in detail from two aspects of hardwareand software, including the whole system scheme, the data acquisition in cable HARTcommunication, wireless HART transmission principle, system software environment building and the main program design process, etc.. In addition, the key technologiesused in the design is introduced simply. Finally, the corresponding program is writtenfor the new HART intelligent instrument, and the scheme is proved feasible throughthe simulation test, achieve the desired goal. |
