Research On K-thermocouple Temperature Measurement System Of Fieldbus

The thermocouple measurement system has gone through tens of years, from the electron potentiometer to intelligent instrument. The rapid development of computer and network technology, especially they combined with automation since 1980's, leading to the Fieldbus technology. Fieldbus has the characters of openness, mutual manipulation and high distribution etc. The appearance of Fieldbus gives a deep innovation of traditional control system. This paper combines the Fieldbus and traditional thermocouple temperature instrument technique to design a thermocouple temperature measurement system of Fieldbus.PROFIBUS-DP using in PLC system takes the major of the market. With its application in control system, the prospective in developing the instruments with PROFIBUS interface is prospective. The temperature data acquisition slave with ASICs is adapted in distributed control systems. The transmitter is more excellent than traditional analog one in the aspects of precision, stability, reliability and anti-jamming ability. Besides that, the slave develops at low-cost and is easy to equip or repair.The slave is designed based on Intel 89C52 MCU serials. ASIC SPC3 realizes the PROFIBUS DP protocol. The use of ASICs facilitates the communication stability of the transmitter, and shortens the developing time. The software develop desktop is Keil uVison2 integrated environment, with the use of SPC3 development package DPS2. The protocols transform layer by layer from PROFIBUS-DP, according to ISO/OSI reference model. The protocol is Master-Slave one.This paper is major in the research of PROFIBUS-DP protocol and SPC3's kernel program, and gives the hardware and software architrave. The measurement system can not only get the exact data from location but also has the function of self-diagnosis, self-alarming and self-compensation.The slave has been connected with SIEMENS SIMATIC S7 system at lab environment. Results approve that the measurement system design is feasible in practice. It can replace the SIEMENS ET-200 PROFIBUS-DP I/O module.With the variable Fieldbus protocol unification and the ASICs production. This slave can equip with PA interface to apply in essential safety area. Also the slave can equip with Ethernet or Hub interface to realize the thought of "control distributed, monitor integrated". In near future we will engage in the development toward the goals above.