Direct calibration of a true-rms ac voltmeter against a He-free pulsed Josephson standard

• Published in: Measurement : journal of the International Measurement Confederation Vol. 236; p. 114981
• Main Authors: Kubiczek, Krzysztof, Durandetto, Paolo, Capra, Pier Paolo, Francese, Claudio, Lanzillotti, Marco, Roncaglione, Luca, Kampik, Marian, Sosso, Andrea
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.08.2024
• Subjects: Josephson arbitrary waveform standard; Quantum metrology; Thermal voltage converter; True-rms voltage calibration; Thermal voltage converter; True-rms voltage calibration; Josephson arbitrary waveform standard; Quantum metrology
• DOI: 10.1016/j.measurement.2024.114981
• ISSN: 0263-2241

Starting from 2019 a new central role is played by quantum standards, owing to the redefined SI, where electrical units are directly linked to the fundamental constants e (elementary charge) and h (Planck constant). Thus, metrologists are nowadays trying to extend the astonishing accuracy attainable in dc measurements to ac and beyond, moving towards calibrations aiming quantum ac voltage generation. Programmable Josephson Voltage Standards are nowadays capable of fulfilling primary metrology requirements only for stepwise-approximated voltage signals up to few hundreds Hz. Pulsed Josephson standards are instead capable of generating arbitrary waveforms at higher frequencies, so are generally called Josephson Arbitrary Waveform Standards (JAWS). Despite of the lower attainable voltage, JAWS are very promising and are the subject of intense research activity. In particular, the capability of generating high spectral purity signals allows high accuracy measurements especially at the low voltage levels (<100mV rms), which are challenging to be performed by the traditional ac-dc transfer difference using thermal converters. We report in the following about our setup for quantum-based calibrations of a true-rms ac voltmeter with low uncertainty, first results obtained and unsolved issues. •The improvement of the cryocooled Josephson Arbitrary Waveform Synthesizer (JAWS).•The system is used for direct and fast calibration of the ac voltmeters.•Thermal issues and EMI have been optimized to synthesize of pure ac sinewaves.•One order of magnitude lower uncertainty than ac/dc transfer methods using TVC.