Temperature Control Algorithm Design And Implementation In Thermal Analysis Furnace

As an important calorimetric analysis tool for material, thermal analyzer is widely used in petroleum, chemical, and materials. Temperature field is one of the key factors affecting detection accuracy of the thermal analyzer. With the rapid development of new materials, new energy and bio- instrumentation, there is increasing demand of thermal analyzer with more widely applications. But domestic temperature control techno logy is relatively backward. Due to domestic thermal analyzer with low temperature control accuracy and poor baseline drift, it cannot meet the needs of detection and research.Based on requirements of multi- mode temperature programmed for thermal analysis, the dynamic characteristics of the furnace are analyzed. With establishing mathematical model of heating rate and temperature for thermal analysis furnace, the control strategy of uniform heating, constant temperature and combination heating for thermal analysis furnace is determined according to the characteristics of the model parameters. The main research includes:For the difficulty of establishing the model in uniform heating process and the lag of adjustment process and othe r issues, Smith fuzzy-PID control algorithm is designed with compensation of heat dissipation. For the large inertia in the process of controlling constant temperature, Segmented Dalin-PID control algorithm is proposed. For the contradictory of heating rate control quality a nd constant temperature control effect, the appropriate switching strategy is determined in the process of combination heating.ATmega128 is the main chip fo r Hardware. N-type thermocouple is selected as temperature sensor with platinum resistance for accurate cold junction compensation, and circuit of 24 high-precision temperature signal acquisition and heating control is designed. the design process of three temperature programmed models is presented in flow chart for Software.The experimental results show that the deviation of hea ting rate is less than 5% using Smith fuzzy-PID control algorithm. with Dalin-PID algorithm, constant temperature control can achieve almost no overshoot, and steady-state error is less than ±0.1℃, the range of baseline drift is in 100μW in the case of combination heating. Temperature control index meets the requirements of rules in A grade. Therefore; the algorithm has good value in the development of thermal analyzer.