Research Of The Intelligent Instrument For Measuring Temperature Based On Neural Network

Each parameter of the diesel engine must be monitored strictly when the diesel engine operates. If it appears abnormal, the reason must be found out and correct measurement must be taken timely so that the machine accident may be avoided. And the cylindrical exhaust temperature of diesel engine is an important parameter, which is an indication of combustion performance. Also it can indicate that whether the combustion is normal, whether the load is even, and so on. In order to measure accurately the cylindrical exhaust temperature of diesel engine, the adjustable digital and intelligent instrument for measuring temperature, of which the reading is immediate and accurate, is designed by incorporating the common temperature-measuring technique of thermocouple, neural network technique and SCM(single-chip microcomputer). In the intelligent instrument, the thermocouple of K style is used as the temperature sensor, and AT89C51 is used as the microprocessor. The exhaust temperature of 12 cylinders can be measured and displayed accurately, and the alarm can be raised when the cylindrical exhaust temperature appears abnormal.The paper is composed of three parts: establishing the mathematical model of thermocouple, designing the hardware and software of intelligent instrument and taking measures to decrease interference of the intelligent instrument.In part 1, the basic knowledge of thermocouple and BP neural network is analyzed;the circuit to take care of signal is designed;the cold end of thermocouple is compensated by AD590. At the same time, the relations between potential of thermocouple and temperature are trained and simulated by MATLAB. And the mathematical model based on neural network is established, which solves the nonlinearity of thermocouple of K style.In part 2, the hardware and software of intelligent instrument are designed. In hardware part, the circuitry of intelligent instrument is designed, which is make up of five parts: the circuit about power, the circuit for measuring temperature, the circuit for A/D transform, the circuit about keyboard and the circuit about display. In thispart, the main chips of each part are introduced, and the interface circuits between these chips and SCM are designed. In software part, Kiel C51 for compiling program is introduced, and the program for measuring temperature is compiled by modularization method. And the nonlinearity of thermocouple of K style is solved, the error due to oxidation of thermocouple is decreased. The needed function of intelligent instrument can carry out.In part 3, the reasons for interference of intelligent instrument are analyzed, and the measures for decreasing interference from the hardware and software are taken. By which the function to decrease interference of intelligent instrument is improved.