ADC型高精密测温电桥非线性误差修正方法研究

针对ADC型测温电桥因电路结构复杂、集成度高、非线性误差来源多样,导致现有误差修正方法效果不佳的问题,提出了一种基于误差来源分析的修正方法。根据ADC型测温电桥原理定量分析了电路中运算放大器共模抑制比、正反向电流不匹配度对非线性误差的贡献,运用RBC开展了这两个误差源的最大似然估计及修正,并对剩余残差进行了多项式拟合,实现了非线性误差修正;基于自制ADC型测温电桥及RBC对上述修正方法进行了验证,实验结果表明:所提方法修正后的最大非线性误差为-1.77×10^-5,相对于传统非线性修正方法的最大非线性误差-3.57×10^-5有了显著提升。

A Nonlinear Error Correction Method for ADC Based High-precision Resistance Thermometry Readout

Due to the complexity of the circuit architecture, high integration and diversity of nonlinear error sources in ADC based resistance thermometry readout, the effect of the existing nonlinear error correction method is not significant. Aiming at these shortcomings, a novel nonlinear error correction method based on the error sources analysis was proposed for ADC based readout. In the method, the influences of the common-mode rejection ratio, the mismatch of the forward and reverse exciting current were analyzed in mathematically. With the resistance bridge calibrator, these two errors were estimated and corrected, Then the residuals were fitted by the linear polynomial. To verify the effect of the proposed correction method, an ADC-based resistance thermometry readout and a resistance bridge calibrators were developed in the study. The experimental results showed that after the correction of the proposed method, the maximum nonlinear error of the readout is -1.77×10^-5, while with the correction of the traditional method, the maximum nonlinear error is -3.57×10^-5. The circuit schematics and measurement procedures of the ADC based thermometry readout were released, this is helpful for the countrys the ADC based high-precision resistance thermometry readout development and commercialized.