Design and Characterization of a Sampling System Based on $\Sigma$–$\Delta$ Analog-to-Digital Converters for Electrical Metrology

This paper describes a sampling system designed using a commercial sigma–delta analog-to-digital converter ($\Sigma$–$ \Delta$ ADC). In addition to characterization measurements using a conventional high-quality signal generator, a Josephson waveform synthesizer that provides ultimately noise- and drift-free voltages was used. To evaluate the suitability of this sampling system as part of a transfer power standard, additional comparisons of the root-mean-square (RMS) values measured were performed against a thermal converter and the primary power sampling standard at the Physikalisch-Technische Bundesanstalt, Braunschweig, Germany. Initial analysis of the measurement data shows an effective resolution in the range of 18–19 bits at an equivalent sampling rate of 64 kHz. The integral nonlinearity error of the system was measured to be within $\pm 7\ \mu \hbox{V/V}$ or one least significant bit at this resolution.