The Hardware Design Of Gas Detection Transmitter Based On HART Bus

Gas detection transmitter, mainly are used for real-time monitoring and recordingconcentration of combustible gases in the environment of industrial productionprocesses, and promptly issue a warning signal to ensure safety in production. HARTbus is increasingly become the fact communication standard of industrialinstrumentation, Gas detection transmitter, as a new instrument industry, also need toadapt to this trend. However, the traditional HART instruments, mostly ware two-wireloop-powered, it requires the whole quiescent current being less than3.5mA, so as toensure the HART signal not be affected. This current limiting made it difficult for someinstruments with large power consumption to take the usual two-wire HART interface.Aiming to this demand, a new solution of three-wire HART interface is proposed in thispaper, and it has been applied on the system of the Gas detection transmitter.The content is divided into five sections:The first part introduces the background of the research, and the current situationand development trend of the Gas detection transmitter and the HART technology. Elicitthe HART technology to be applied on the Gas detection transmitter, the research topicof this paper is established.The second part describes some theory and knowledge involved in this study,including the theory of combustible gas detection sensors and HART bus protocol.Initially introduce the Gas detection transmitter’s typical application methods in realsystems and the general process of signal processing.The third part describes the whole solution and the hardware system design. First,according to the actual needs, set the design specification requirements andscheme.Then a detailed description of the hardware design of the whole system is betaken, includes gas detection signal chain, the processor system, HART communicationinterface, human machine interaction module and power distribution systems, etc. Thepart of the HART communication interface is with a detailed design description, mainlyfor the principle of the realization of three-wire type of HART interface, chip selectionand features of networking application. It is also do a simple description about thesystem layout and PCB design.The fourth part mainly describes software design of HART communication and theimplementation of HART command system about Gas detection transmitter. The fifth part details each test session in the entire product design process, includeshardware board test, the function and performance of whole system, like the quality ofgas detection and the performance of HART communicaton. Finally, some reliabilitytests are taken.The sixth part make a summary, noting that the results achieved and theshortcomings.The design of Gas detection transmitter based on HART bus finally wassuccessfully achieved a three-wire interface communication, avoid the restrictions onpower consumption, also be compatible with traditional DCS applications, and achievethe communication with some common host device, like the HART Communicator,HART gateway, HART module. The whole system is also through professional testingof Gas monitoring device industry, and achieves the specification requirements.