横电磁波小室校准系统产生标准电场的不确定度评定

Uncertainty Evaluation of the Reference Electric Field Generated by the Transverse Electromagnetic Cell Calibration System

电场传感器需要通过校准才能应用于电场测量,校准系统的不确定度反映了传感器校准结果的可信赖程度,所以需要评定校准系统的不确定度。横电磁波(TEM)小室具有成本低、内部电场均匀性好、幅值较高等优点,适用于产生标准电场,进行电场传感器的校准工作。针对光电集成电场传感器的校准需求,建立了一套TEM小室电场传感器校准系统,分析了该系统产生标准电场的各项影响因素包括场均匀系数、TEM小室特征阻抗实部、半空间距离和净输入功率,计算了这些影响因素的标准不确定度。通过不确定度合成,得出TEM小室校准系统在≥95.45%的置信概率下,产生标准电场的扩展不确定度为5.9%,满足校准电场传感器的需求。

Electric field sensors should be calibrated before field measurements.The uncertainty of the calibration system reflects the reliability of the calibration data,so the system should be carefully evaluated.TEM cells are widely used for calibrations of electric field sensors due to their low price,perfect uniformity,and relatively high intensity of the electric field inside.To meet the needs of optic-electric integrated electric field sensors＇calibration,a TEM cell calibration system was constructed.The uncertainty contributors,i.e.,the electric field uniformity coefficient,the cell＇s characteristic impedance,the half-space distance,and the net power delivered to the cell,were carefully analyzed and their standard uncertainties were calculated respectively.According to the rule of uncertainty propagation,the whole system＇s expanded uncertainty is 5.9% under the coverage probability not lower than 95.45%,which meets the requirements of calibration.