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Quantum technologies

Josephson primary standard for voltage

Independent, traceable measurements

This service is designed for organisations that require accurate voltage measurements, including developers and suppliers of high performing voltage products or organisations needing to meet a legal standard or specification. It allows more rapid testing of instruments and products or enables realisation of top level characterisation service.

DC voltage measurements at NPL are traceable to the SI volt via the Josephson effect, which establishes an accurate potential difference based on the fundamental constants, h and e, and frequency. We are able to offer direct access to a quantum standard, which means that measurements have low uncertainty and are independent, traceable and internationally recognised.  We are able to offer a customisable solution, which is ideal if you are interested in integrating with other systems or incorporating into a production line. We also provide full training in the technology and practical measurements.

The Josephson system is: 

  • directly traceable to a quantum standard
  • a proven system design which is used for all voltage calibrations at NPL, with a 20 year track record
  • Fully isolated system enabling the measurement of commercial transfer standards when operating on continuous mains power
  • designed for direct calibration of electronic Zener reference standards at 1V and 10 V. The primary standard is realised via a Josephson junction array operating at 4.2 K biased with a radiofrequency at 16 GHz
  • verified through international comparisons of voltage BIPM-EM-K10.a, BIPM-EM-K10.b and EUROMET.EM.BIPM-K11 
  • supplied with a year’s warranty for the complete system

NPL has an active programme of research in electrical quantum metrology and is part of the wider group of quantum experts in Euramet and further afield. By adopting this solution, NPL customers get access to this knowledge base through the our experts. NPL carried out a direct comparison with the BIPM using its own design of Josephson voltage standard and achieved an uncertainty of better than 1 part in 109 (0.2 parts in 109). Systems we supply use the same principles and instruments having the same specifications in order to guarantee this level of performance.

The NPL Josephson voltage standard is fully automated and is used to calibrate customer Zener references on a routine basis. Measurement software provides all the necessary set-up, measurement and data analysis functionality. A complete Zener measurement typically takes 5 to 10 minutes. The system at NPL is suitable for operation by junior technicians (sometimes graduate level, but often technical college level) following 1 or 2 weeks of training and supervision.

NPL can also provide installation and training package, covering set-up, operation, maintenance and troubleshooting, also measurement theory, best practice, data analysis, measurement uncertainty and data reporting. On-going technical support is also available.

Don’t see what you are looking for? Our diverse skill set enables us to provide bespoke solutions. Please contact us to discuss your requirements.

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Measurement for Quantum

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Announcing a new programme to support the UK quantum industry through access to specialist science and engineering advice and facilities.

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