A new automatic reference and switching unit for calibration of high value resistors in the range 100 kΩ to 10 TΩ

We describe a Reference and Switching Unit (RSU), that, with a digital multimeter (DMM) and a dc voltage calibrator, constitutes a system for calibration of standard resistors in the range 100 kΩ–10 TΩ at measurement voltages up to 1000 V. This system represents an implementation of a DMM-based system already developed at IEN. We report the characteristics of the DMM-based system, the metrological and electronic features of the RSU, the uncertainty levels that can be achieved with the DMM-based and whit the RSU-based systems. Finally, we show the obtained results in order to check the compatibility of the two systems in the calibration of standard resistors in the range 1 GΩ–1 TΩ. The 2σ best measurement capabilities of the RSU-based system span from 6.3×10⁻⁶ for the calibration of a 100 kΩ standard resistor at 10 V, to 1.2×10⁻³ for the calibration of 10 TΩ standard resistor at 1000 V.