Sampling measurement using a programmable Josephson voltage standard system toward low-frequency AC voltage standard

We are developing a differential sampling measurement system to measure low-frequency sinusoidal waveforms using an AC-Programmable Josephson voltage standard (AC-PJVS) system. Our AC-PJVS circuit is composed of NbN-based over damped Josephson junctions cooled with a compact cooler. We have measured sinusoidal waves of 62.5 Hz at the root mean square (rms) voltage of 3 V using our sampling measurement system. Experimental result shows that the type A uncertainty is 1.9 μV/V (k =1).