An automated Josephson based ac-voltage calibration system

This paper describes a new calibration system developed at INMETRO to guarantee traceability of low-frequency alternating (ac) voltage calibrations (up to around 1 kHz) to a programmable Josephson ac waveform synthesizer. The automated full synchronous system allows the synchronization of a calibrator or signal synthesizer with a programmable Josephson voltage synthesizer system to be made by employing digital sampling and data processing techniques, aided by adaptive digital control. Digital regulators allow synchronization between signals with nanoradian resolution and thus the correct determination of their spectral content.