Differential Sampling Measurement of a 7 V RMS Sine Wave With a Programmable Josephson Voltage Standard

A 10 V programmable Josephson voltage standard has enabled sine waves with voltages up to 7 V RMS to be accurately measured with a differential sampling measurement technique. Expanding the voltage range for this technique enables the direct calibration of the low-frequency ranges of commercial calibrators in the ac voltage mode. This paper reviews the practically achievable performance and challenges of the differential sampling measurement technique that arise when measuring RMS voltages greater than a few volts. A relative Type A uncertainty of 4 parts in 10⁷ was achieved with the technique when measuring a 7 V RMS sine wave generated by a calibrator at 62.5 Hz.