低温铂电阻变送器设计

Design of Low Temperature Transducer

针对特种气体制备过程低温监控的需求,设计了基于铂电阻的二线制低温变送器,论述了其组成及原理、软硬件设计与实现方案。变送器采用"A/D+微处理器+D/A"的设计方法,充分发挥每个元件的性能,ADS1220实现A/D采集并为采集电路提供恒流源,AD5421实现更高精度的D/A转换并为其他器件供电。通过建立"温度-电阻-电流"的对应关系,采用查询与线性插值相结合的方法,经过软件滑动平均滤波,实现稳定的低温4.2 K^370 K的测量,系统测量绝对误差小于0.1%。

To meet the demand for acquiring low temperature in the preparation process of special gas,the two-wired temperature transducer based on platinum resistance is designed. Its composition,principle,hardware and software implementations is introduced. The ＂A/D＋ microprocessor＋ D/A＂ design approach is adopted,and the performance of each component is fully realized. ADS1220 realizes A/D acquisition and provides constant current source for acquisition circuit. AD5421 realizes D/A conversion with higher accuracy and supplies power for other devices. The temperatureto-resistance-to-current table is establish. The table searching and linear interpolation is combined. The sliding average filtering is applied to achieve ultra-low temperature measurement in the range of 4.2 K^330 K. The absolute error of the temperature transducer is less than 0.1%.