Analog-to-digital conversion for low-frequency waveforms based on the Josephson voltage standard

Abstract

A waveform synthesizer adopting a superconductor-normal metal-superconductor junction array has been developed, which can generate arbitrary stepwise waveforms with a number of quantum-voltage steps up to 1 V level amplitude. As an application of the synthesizer, we have built a sampling voltmeter that measures the differential voltages between a sinusoidal waveform produced by a semiconductor-based ac source and the Josephson waveforms. We carried out extensive sampling measurements for a 50 Hz sine wave with 1 V amplitude, applying sampling apertures in the range of 55 μs t a 130 μs and using Josephson waveforms with 32, 60, 80 and 100 quantum steps. From the measurements, the amplitude of the ac waveform was determined with a type A uncertainty (k = 2) of 0.15 μV. Also, we elucidated how the phase jitter in the ac waveform is reflected in the overall uncertainty for the measurements. The type B uncertainty due to the jitter is at least one order of magnitude smaller than the type A uncertainty.

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

“…However, the accuracy of the differential sampling measurements, with this configuration, relies on the common-mode rejection ratio (CMRR) capabilities of the sampling DVM. The error induced by the CMRR of the Agilent 3458A is about 1 part in 10 7 (140 dB) [8]. The guard of the DVM is driven by the calibrator sine wave in order to reduce the influence of capacitive effects.…”

“…The quantities reported graphically (see Figs. [3][4][5][6][7][8][9][10][11] are V CALIBRATOR and Unc. (V CALIBRATOR ) with k = 2.…”

Development of Josephson voltage standards

“…www.intechopen.com minimum number of samples, frequencies up t o 6 k H z h a v e b e e n u s e d t o c a l i b r a t e impedance ratios (Lee et al, 2011), while typically 16 to 256 samples reduce the bandwidth to clearly below 1 kHz (Kim et al, 2010). Another way to minimize the effect of transients is to use the rectangular waveforms and to just look at the fundamental tone of the waveform.…”

Precision ac-dc difference measurements of a thermal transfer standard based on a Josephson sampling voltmeter

“…The Josephson synthesizer can be applied as a reference signal generator for a differential sampling voltmeter [6]- [10]. The sampling voltmeter digitizes an output waveform of a semiconductor-based source in reference to the Josephson waveforms.…”

“…In our previous work [10], we built a sampling voltmeter adopting a Josephson waveform synthesizer, and made extensive differential sampling measurements of a 50-Hz and 0.7-V level waveform produced by a semiconductor-based ac source in various measurement parameters. From the measurements, we could determine the amplitude of the waveform with an uncertainty less than 0.15 µV (k = 2).…”