Biography

Jonathan Williams joined NPL in 1983 with a degree in Physics from Oxford University. Since 1988 he has been working on the application of cryogenic techniques to electrical metrology. He has developed a number of cryogenic current comparator systems including resistance ratio bridges for the quantised Hall effect as well as resistance standards operating at currents from 100 A to 100 nA. More recently he has been developing measurement systems for the direct synthesis of voltage waveforms in terms of the Josephson effect.

Jonathan is a Fellow of the Institution of Engineering and Technology, a Chartered Engineer and a Liveryman of the Worshipful Company of Scientific Instrument Makers. In 2011, he was awarded a PhD from City University for his thesis 'Realisation of quantum standards for electrical metrology and their role in the SI'.

Committees

Jonathan is the chairman of the Working Group on Low Frequency Quantities (WGLF) of the Consultative Committee for Electricity and Magnetism (CCEM).

Selected publications

• A low noise preamplifier with optoelectronic overload protection for radioactivity measurement
  J. P. Sephton, J. M. Williams, L. C. Johansson, and H. C. Philips
  Appl. Radiat. Isot., 70, 2047-2050 (2012)
• Quantum-referenced voltage waveform synthesiser
  J. M. Williams, D. Henderson, J. Pickering, R. Behr, F. Muller, P. Scheibenreiter
  IET Science Measurement & Technology 5, 163 (2011)
• An automated cryogenic current comparator resistance ratio bridge for routine resistance measurements
  J. M. Williams, T. J. B. M. Janssen, G. Rietveld, E. Houtzager
  Metrologia 47, 167 (2010)
• The quantum metrology triangle and the redefinition of the SI ampere and kilogram; analysis of a reduced set of observational equations
  M. J. T. Milton, J. M. Williams, A. B. Forbes
  Metrologia 47, 279 (2010)
• Synthesis of precision waveforms using a SINIS Josephson junction array
  R. Behr, J. A. Williams, P. Patel, T. J. B. M. Janssen, T. Funck, M. Klonz
  IEEE Transactions On Instrumentation And Measurement 54, 612 (2005)
• The simulation and measurement of the response of Josephson junctions to optoelectronically generated short pulses
  J. M. Williams, T. J. B. M. Janssen, L. Palafox, D. A. Humphreys, R. Behr, J. Kohlmann, F. Muller
  Superconductor Science & Technology 17, 815 (2004)

Related links

• IMC's Callendar Medal awarded to Dr Jonathan Williams (NPL news story)
• SI Base Units (YouTube video)

Contact details

Email: jonathan.williams@npl.co.uk
Tel: 020 8943 6376