Design Of Two-wire Intelligent Temperature Transmitter

With the development of electronic technology, the emergence of various digital devices,intelligent instruments is used in production process more and more widely, to collection,transition and treatment of signal, put forward higher requirements. The collection oftemperature and processing is widely applied to the industrial field data collection system, andthe temperature signal into4～20mA industrial standard signal transmission, become theindustry must complete a link. At present, intelligent temperature transmitter in the use ofintelligent instruments have a large share of, intelligent temperature transmitter in the researchof realistic significance.This paper introduces a kind of two wire intelligent temperature transmitter which takesSTC89C52as the core, gives the hardware and software design method of temperaturetransmitter, gaves a detailed introduction on the acquisition and processing of front-end signaland the realization of V/I convert circuit. In the hardware design, STC89C52as microcontroller,DSl8B20as digital temperature sensor, LCD1602as LCD monitor, A/D converter usesTLC2543and D/A converter uses TLC5615. This paper writes C language program and debugsby Keil uVision4. Microprocessor is the core of intelligent temperature transmitter, uses theSTC89C52microcontroller whose unique function and flexibility can meet the requirements ofdesign. Through OP07, the temperature transmitter magnifies millivolt voltage signal whichtested by K type thermocouple to0~5V standard voltage signal, which converts to digitalsignal through the TLC2543for A/D conversion processing, and transported into single chipmicrocomputer STC89C52. The thermocouple cold end temperature compensation measures byDS18B20, the output can be directly connected with the single chip microcomputer. In theSCM, it realizes filtering, cold end temperature compensation, linear and scale transform bysoftware, then the tested temperature value is sent to LCD and displays, meanwhile, convertsthe digital quantity into analog quantity through TLC5615, then outputs4~20mA DC standardcurrent signal through V/I transform circuit.This design is simple, good stability, on Proteus7.5platform, it does hardware andsoftware simulation. Through the Proteus software to temperature transmitter work statesimulation, used to test the feasibility of the design and shorten the development cycle of thesystem, reduce development costs, it is a kind of effective feasible simulation method.