Design Of High-Precision And Wide Temperature Range Measurement And Control System

With the development of technology, the accuracy of measurement in the fieldof precision engineering also has evolved very much. At present the influence ofenvironment temperature must to be considered which become more and moreimportant in precision measurement. Precision measuring instruments generallyrequire temperature calibration to improve the measurement accuracy by correcterrors caused by temperature. Therefore, developing a wide temperature range ofhigh-precision temperature control system has an important meaning and purpose.On the basis of summing up past experience in temperature control, the paperdevelops a constant temperature box control system. Making use of systemidentification toolkit of MATLAB, the mathematic model of the system can beidentified. PID control algorithm and fuzzy control mechanism are introduced.Computer simulation of PID and fuzzy algorithm is completed.The function of control system is divided into two parts, includingrefrigeration and heating. The host computer software is programmed byLabVIEW.PID cooling control algorithm and fuzzy controller design for heatingcontrol are programmed in LabVIEW soft. The transient time is reduced by usingsemiconductor and refrigeration. Heating control function is achieved by usingfuzzy controller and PWM technology.The experimental results show that temperature control accuracy of asingle-point is less than±0.02°C and the whole field is within±0.03°C. And thecontrol accuracy can be still ensured on the condition of that some heat sources areintroduced in constant temperature box. The feasibility of heating control system isconfirmed by heating control experiments. The temperature control within certainwide range is achieved.