The Comité International des Poids et Mesures (CIPM) acting in accordance with Resolution 7 of the 18th Conférence Générale des Poids et Mesures (1987) has adopted the International Temperature Scale of 1990 (ITS-90) to supersede the International Practical Temperature Scale of 1968 (IPTS-68).
The CIPM notes that, by comparison with the IPTS-68, the ITS-90
extends to lower temperatures, down to 0.65 K, and hence also supersedes the EPT-76,
is in substantially better agreement with corresponding thermodynamic temperatures,
has much improved continuity, precision and reproducibility throughout its range and
has subranges and alternative definitions in certain ranges which greatly facilitate its use.
The CIPM also notes that, to accompany the text of the ITS-90 there will be two further documents, the Supplementary Information for the ITS-90 and Techniques for Approximating the ITS-90. These documents will be published by the BIPM and periodically updated.
The CIPM recommends
that on 1 January 1990 the ITS-90 come into force and
that from this same date the IPTS-68 and the EPT-76 be abrogated.