过程校验仪校验热电阻输入模块误差分析

Error Analysis for the Process Calibrator Calibrating Thermal Resistance Input Module

针对某过程校验仪校验热电阻信号输入模块时存在的温度数据误差率达8.45%的异常现象,开展实验研究。将温度测量转换为电阻测量问题,分别设计了应用过程校验仪及精密电阻箱进行校验的实验。实验数据显示,前者的电阻值测量数据平均误差率为14.1%,后者误差率仅为0.21%。然后通过数据分析,提出假设。实验验证了模块电阻测量值与校验仪输出值的比等于两者激励电流之比的规律。两者激励电流不一致导致产生测量误差;建议选用精密电阻箱校验模块,若使用校验仪,需要确保与被校验设备的激励电流相等。

Aiming at a process calibrator’s 8.45% temperature error rate in checking thermal resistance signal input module, the experimental research was carried out. In which, measuring temperature was transformed into measuring the resistance, and the experiment on both process calibrator and precision resistance box was designed for the checking operation. The experimental data shows that, the error rate averaged of the former is 14.1% while that of the latter is only 0.21%.The data analysis, hypothesis and experimental verification prove that, the ratio of the module’s measured value to the calibrator’s output value equals to the ratio of both excitation currents. The research result indicates that the difference of two excitation currents can incur this measurement error. The precision resistance box should be recommended to verify this module. In case that a calibrator will be used, ensuring calibrator’s excitation current equals to the device’s becomes necessary.