基于TEC和PID的恒温控制系统

Constant temperature control system based on PID regulation

摘要:

量热法可用于表征放射性核素衰变热功率。基于热平衡模式的量热系统，测量过程对测试环境波动较为敏感，测量精度受环境温度影响较大，因而对环境温度稳定性要求较高。为向量热系统提供稳定的恒温测试环境，基于LabWindows/CVI虚拟仪器开发平台，以半导体制冷器（Thermo Electric Cooler，简称TEC）为制冷元件、Pt100型铂电阻温度传感器为测温元件、高精度数字源表作为电源、高精度数字多功能表为温度测量仪表，基于网络通讯，采用比例-积分-微分（Proportion-Integration-Differentiation，简称PID）控制策略，设计开发了量热计恒温控制系统。开发完成的系统软件可实现仪表通讯、数据采集与显示、恒温控制、数据分析与存储功能。以量热系统恒温层结构材料铝锭为对象进行了恒温效果测试，测试时长48 h，远高于量热系统单位测量周期。结果显示，该恒温系统可获得±0.2℃的控温精度，满足量热测试对系统环境温度稳定性的要求。

Abstract:

Calorimetry is an alternative for thermal power characterization of radionuclide decay. Calorimetric system working at thermal equilibrium mode is sensitive to environmental fluctuations during the measurement process and its measurement accuracy is easily effected by environmental temperature fluctuations. As a result, high stability of environmental temperature is required by calorimetry. In order to provide a stable constant temperature environment for the calorimetric system, a temperature measurement and control system based on LabWindows/CVI virtual instrument development platform was designed and developed. The system employed thermoelectric cooler as refrigeration element, Pt100 platinum resistance temperature sensor as temperature measurement element, high-precision digital source meter as power supply, high-precision digital multifunction meter as temperature measurement instrument, network communication, and a Proportion-Integration-Differentiation algorithm which is referred as PID algorithm as control strategy. The completed software realized functions of instruments communication, data acquisition and display, temperature control, data analysis and storage. A temperature control performance test was performed on thermostatic layer of aluminum ingots in calorimetric system for 48 hours which is far longer than time required for single calorimetric test. Result shows that the temperature control system is able to achieve a temperature control accuracy of ±0.2°C, which meets environment stability requirement for the calorimetric system.