An Approach for Reliable Calibrations of Ultra-high Value Resistors with the Dual Source Bridge

At the Istituto Nazionale di Ricerca Metrologica (INRiM), an approach for reliably calibrating ultra-high-value resistors with the dual source bridge (DSB) is proposed as part of the INRiM knowledge transfer task. This approach is particularly suitable for commercial DSBs, which can be used by electrical calibration laboratories for their activities for external clients. The approach is based on ratio measurements, metrological triangulation rule and measurement compatibility. The proposed reliable calibration value is the corrected weighted mean of three intermediate calibration values which must satisfy a strict triangulation rule and be compatible within small uncertainties. This approach helps to reduce systematic errors or to include them into the uncertainty of the corrected weighted mean. For this paper the method was applied to three high value resistors using a commercial DSB to obtain a reliable calibration value of a 1 PX resistor. This technique meets the requirements of the EN 17025 standard for risk assessment of calibration activities.