Recommendation 1 of the 77th CIPM (1988)

Representation of the volt by means of the Josephson effect

The Comité International des Poids et Mesures,

acting in accordance with instructions given in Resolution 6 of the 18th Conférence Générale des Poids et Mesures concerning the forthcoming adjustment of the representations of the volt and the ohm,


  • that a detailed study of the results of the most recent determinations leads to a value of 483 597.9 GHz/V for the Josephson constant, KJ, that is to say, for the quotient of frequency divided by the potential difference corresponding to the n = 1 step in the Josephson effect,
  • that the Josephson effect, together with this value of KJ, can be used to establish a reference standard of electromotive force having a one-standard-deviation uncertainty with respect to the volt estimated to be 4 parts in 107, and a reproducibility which is significantly better,


  • that 483 597.9 GHz/V exactly be adopted as a conventional value, denoted by KJ 90 for the Josephson constant, KJ,
  • that this new value be used from 1 January 1990, and not before, to replace the values currently in use,
  • that this new value be used from this same date by all laboratories which base their measurements of electromotive force on the Josephson effect, and
  • that from this same date all other laboratories adjust the value of their laboratory reference standards to agree with the new adopted value,

is of the opinion that no change in this recommended value of the Josephson constant will be necessary in the foreseeable future, and

draws the attention of laboratories to the fact that the new value is greater by 3.9 GHz/V, or about 8 parts in 106, than the value given in 1972 by the Comité Consultatif d'Électricité in its Declaration E 72.

DOI : 10.59161/CIPM1988REC1E

The reader should note that the official version of this Resolution is the French text


The 26th CGPM in 2018 (Resolution 1) abrogated the adoption of a conventional value for KJ.

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