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1976 |
In 1976 the CIPM approved a new low-temperature scale called the 1976 Provisional 0.5 K to 30 K Temperature Scale, or EPT-76. Its purpose was to provide a unified Scale upon which temperature measurements could be made in this range, pending the revision and downward extension of the IPTS-68. It was defined in terms of the temperatures assigned to eleven fixed points within the range 0.5 K to 30 K, together with the differences between T76 and the following existing scales: IPTS-68; the 4He-1958 and 3He-1962 vapour pressure scales; NPL-75 and the NBS version of IPTS-68 which was defined by difference from NBS-55. In contrast to IPTS-68, the EPT-76 could thus be realized in a number of ways; either by using one of the above scales and the tabulated differences given in the text of EPT-76 or by using a thermodynamic interpolating thermometer, such as a gas thermometer or magnetic thermometer, calibrated at one or more of the specified reference points of EPT-76.
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