Differential sampling measurement of a 7 V rms sine wave and a programmable Josephson voltage standard

A 10 V programmable Josephson voltage standard has enabled sine waves with rms voltages up to 7 V to be accurately measured with differential sampling methods. This paper reviews the challenges and limitations of differential sampling that arise when rms voltages greater than a few volts are measured. Preliminary measurements confirmed the capability of the NIST 10 V Josephson array to perform this task and emphasize the need for highly stable and low-phase-noise ac sine wave voltage sources in order to further reduce the measurement uncertainty¹.