基于半导体控温的高精密低漂移测温系统

High Precision Low-Drift Temperature Measurement System Based on Thermoelectric Cooler

针对绝热加速量热仪对样品微弱放热的检测需求,设计了一种基于冷端及测量电路半导体恒温控制的高精密低漂移热电偶测温系统。系统采用低噪声仪用放大器ISL28634及32位高分辨率模数转换器AD7177-2实现热电偶信号数字化采集;通过高灵敏度NTC热敏电阻进行热电偶冷端测温补偿;利用半导体制冷片针对性控制模拟电路部分温度,使其工作于恒温稳定状态,抑制电路测温漂移。实验结果表明,系统在0~450℃范围内测温精密度优于±0. 005℃,2 h内平均每min测温漂移优于±0. 000 5℃。同时,将该系统应用于绝热加速量热仪,可有效提升仪器热安全评价指标——起始反应温度检测准确度。

Aiming at the weak exothermic reaction detection requirement in the accelerating rate calorimeter,a kind of high precision low-drift thermocouple temperature measurement system was proposed in this article based on cold end and measuring circuit semiconductor thermostat control.In this system,a low-noise instrumentation amplifier ISL28634 and a 32-bit high resolution analog-to-digital converter AD7177-2 were used for digitizing the thermocouple signals.The cold junction temperature of thermocouple was carried out by using a high sensitive NTC thermistor.The partial temperature of the analog circuit was controlled by means of semiconductor refrigeration chip,the temperature of the analog circuits was controlled in a constant state,thus,the temperature drift was suppressed.The experimental results show that the temperature measurement precision is better than±0.005℃and the average temperature drift per minute in 2 h is better than±0.000 5℃,in the range of 0~450℃.Meanwhile,the application of this system to adiabatic accelerometer can effectively improve the thermal safety evaluation index of the instrument,that is initial reaction temperature detection accuracy.