Research And Design Of The Intelligent Instrument For Measuring Temperature

In industrial process control,temperature is an important measurement parameter.Because of the advantages,such as high accuracy and wide temperature range and low in cost,the thermocouple become the first choice for temperature measurement in industrial applications.For the accurate of temperature measurement, the dissertation combine with the traditional thermocouple temperature measurement technology,neural network technology and the single-chip technology,and designed the intelligent measurement temperature instrument with intuitive reading and high accurate.The MCU of the instrument is the single-chip microprocessor AT89S52, K-type thermocouple(Ni-Cr-Ni-Si) is the temperature sensor,DS18B20,which as a digital temperature sensor,for measuring temperature of thermocouple cold junction, in order to compensate the thermocouple cold junction compensation.The dissertation is composed of three parts,which are the intelligent thermometer hardware design,software design and mathematical model of the thermocouple.Fristly,designed the hardware of the intelligent temperature measurement instrument.The hardware of the intelligent temperature measurement instrument is composed of five major components:microcontroller,signal conditioning circuits, analog-to-digital conversion circuits,keyboard input circuits and the liquid crystal display circuits.And introduce the devices and interface circuits of these components in the dissertation.Finally analyzed the causes of interference,improved the the anti-interference performance of intelligent temperature measurement instrument through analysis and taking anti-interference measures.Secondly,designed the softwares of the instrument by modular programming, which are formd by MCU software and PC software.The entire application programs of MCU include the main program of the system,data acquisition,display routines and keyboard modules.Data collection of the host computer collect data with serial communication,and by modular programming.PC software system is divided into several independent functional modules,each module completed identified mission, and designed software wthe friendly display interface and data storage functions with LabVIEW.Finaly,analyzed basic knowledge of the thermocouple and the PID neural network,designed a rationale thermocouple Signal conditioning circuit,and solved the thermocouple cold junction compensation used the digital temperature sensor.At the same time,train and simulate the relationship between the thermocouple temperature and the thermoelectric potential with MAfLAB,and build mathematical model based on the PID neural network,which solved the non-linear in measurement of the K-type thermocouple(Ni-Cr-Ni-Si).