Standard Article

Metrology of Time and Frequency

  1. Felicitas Arias1,
  2. Andreas Bauch2

Published Online: 15 MAR 2011

DOI: 10.1002/3527600434.eap703

Encyclopedia of Applied Physics

Encyclopedia of Applied Physics

How to Cite

Arias, F. and Bauch, A. 2011. Metrology of Time and Frequency. Encyclopedia of Applied Physics. 315–348.

Author Information

  1. 1

    Bureau International des Poids et Mesures, Sèvres cedex, France

  2. 2

    Physikalisch-Technische Bundesanstalt, Braunschweig, Germany

Publication History

  1. Published Online: 15 MAR 2011


This chapter provides a concise overview of the current status of time and frequency metrology. The definition of the time unit and of time scales is given, and the standards and procedures to realize them are described. The measures by which their properties are characterized are explained. The comparison of remote standards is discussed to the extent that it is a prerequisite for the realization of a world reference time scale by the Bureau International des Poids et Mesures (BIPM). Only a brief account is given on the various means of disseminating time and the wide applications thereof. The reader is invited to use the literature in the Further Reading section as well as the numerous references to get a deeper insight into the field.


  • time measurement;
  • atomic frequency standard;
  • Ramsey cavity;
  • maser;
  • primary frequency standard;
  • Galileo system time