Abstract: In view of the problems of the inability to continuously change the heating rate of the existing heating plate control system, large temperature impulse, and poor manmachine interaction, a set of heating plate control systems based on PID adjustment was designed to change the heating rate continuously. The system was based on PID regulation to control the heating plate to heat at a constant rate or a continuously changing rate. It can monitor the temperature and time of insulation in realtime, adjust the impulse of temperature, and save data. The upper computer software in the control system used Visual Basic 6.0 language as a development tool. The main function modules include a menu bar, serial communication, temperature display, parameter setting, parameter display, and reminder. The design of this computer program included sensor calibration, heating rate, temperature holding, data acquisition, and pretreatment subprograms.The performance of the heating block system was tested using milk, mashed potato, and walnut shell powders as representative liquid, semisolid, and solid materials under the heating rates of 0.1 ℃/min, 0.5 ℃/min, 1 ℃/min, 5 ℃/min, and 10 ℃/min, respectively. The results showed that the range of heating rate of the heating block system could reach 0.1-13.35 ℃/min, the accuracy of heating rate and target temperature was within ±0.1 ℃/min and ±0.3 ℃, respectively. The heating rate and final target temperature were controlled accurately under multiple heating rates. The maximal temperature overshoot of the solid sample can be controlled below 0.5 ℃ under the intelligent mode. This system can meet the requirement of experimentally determining the thermal inactivation kinetics of microorganisms.

Key words: heating block control system, heating rate, target temperature, intelligent mode, upper computer software, control accuracy

摘要： 针对现有加热板控制系统存在的不能连续改变加热速率、温度上冲量大和人机交互感差等问题，研发一套基于PID调节的可连续改变加热速率的加热板控制系统。该系统基于PID调节控制加热板以恒定的速率或连续改变的速率加热，实时监控保温温度和保温时间，调整温度上冲量，以及保存数据。控制系统中上位机软件以Visual Basic 6.0语言作为开发工具，主要功能模块包括菜单栏、串口通信、温度显示、参数设置、参数显示和提醒。程序设计包括传感器校准、加热速率、保温温度、数据保存和预处理等子程序。试验分别选取牛奶、土豆泥和核桃外壳粉为代表的液体、半固体和固体材料，以常用的0.1 ℃/min、0.5 ℃/min、1 ℃/min、5 ℃/min、10 ℃/min加热速率，对新加热板控制系统进行测试。试验结果表明，加热板的可控加热速率范围为0.1~13.35 ℃/min，加热速率控制精度为±0.1 ℃/min，保温温度的控制精度为±0.3 ℃/min；在连续改变速率的加热模式下，加热板仍能精确控制温度上升的速率和最终的保温温度；智能模式下，控制系统能将最难控制的固体样品的最大温度上冲量控制在0.5 ℃以下，满足微生物热致死动力学研究中对温度控制精度的要求。

关键词: 加热板控制系统, 加热速率, 目标温度, 智能模式, 上位机软件, 控制精度