高精度热电偶测温电路设计与分析

Design and Analysis of High Precision Thermocouple Temperature Measurement Circuit

摘要:

在工业现场影响热电偶测温精度的因素是多方面的,除热电偶本身误差外,主要是输入通道误差、冷端补偿误差和分度表非线性校正误差。围绕以上三个主要因素,设计了一种可应用于复杂工业环境的高精度热电偶温度测量电路,结合设计方案针对于前两种因素在深入分析误差内在机理基础上给出误差计算公式。针对非线性校正误差提出一种等精度最小二乘拟合校正算法,使用该算法可根据校正精度要求,将测温范围自动划分等精度区间与传统插值法相比,在不增加计算量的前提下大大提高了校正精度。提出的误差计算公式和非线性校正方法,对于高精度热电偶测温电路的设计具有适用性和重要的指导性,经实际应用验证设计方法满足了复杂工业环境下高精度的测温要求。

Abstract:

There are many factors that affect the accuracy of thermocouple temperature measurement in the industrial field. In addition to the error of the thermocouple itself, it is mainly the input channel error, the cold junction compensation error, and the non-linear correction error of the reference table. Focusing on three main factors, era high-precision thermocouple temperature measurement circuit that can be applied in a complex industrial environment is designed. The error calculation formula is given based on the in-depth analysis of the internal mechanism of the errors for the first two factors in combination with the design scheme. An equal-precision least-square fitting correction algorithm is proposed for nonlinear correction errors. Using this algorithm, the temperature measurement range can be automatically divided into equal-precision intervals according to the correction accuracy requirements. Compared with the traditional interpolation method, without increasing the amount of calculation greatly improve the correction accuracy. The proposed error calculation formula and nonlinear correction method have applicability and important guidance for the design of high-precision thermocouple temperature measurement circuit. It has been verified by practical application that the design method can meet the requirement of high precision temperature measurement in complex industrial environment