Evaluation of Linearity Characteristics in Digital Voltmeters Using a PJVS System With a 10-K Cooler

We have evaluated the linearity of commercial digital voltmeters (DVMs) using a programmable Josephson voltage standard (PJVS) system. The PJVS system is composed of a 524288-niobium nitride-based Josephson junction array that has the ability to generate arbitrary output voltages up to 17 V with a resolution of 12 bits. In our system, the junction array is operated in a 10-K compact cooler without a liquid-helium coolant. Up to now, we have succeeded in generating accurate dc voltage levels of up to approximately 13 V using this system. In this paper, we demonstrate our PJVS system as a tool for investigating the linearity characteristics of commercial DVMs, with an accuracy level of 0.1 μV/V or better, and discuss the uncertainty sources in these measurements.