The Provisional Low Temperature Scale of 2000 (PLTS-2000) is an equipment calibration standard for making measurements of very low temperatures, in the range of 0.9 mK (
millikelvin) to 1 K, adopted by the
International Committee for Weights and Measures in October 2000. It is based on the melting pressure of solidified
helium-3
Helium-3 (3He see also helion) is a light, stable isotope of helium with two protons and one neutron (the most common isotope, helium-4, having two protons and two neutrons in contrast). Other than protium (ordinary hydrogen), helium-3 is the ...
.
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At these low temperatures, the melting pressure of helium-3 varies from about 2.9
MPa to nearly 4.0 MPa. At the temperature of approximately 315 mK, a minimum of pressure (2.9
MPa) occurs. Although this gives a disadvantage of non-
monotonicity, in that two different temperatures can give the same pressure, the scale is otherwise robust since the melting pressure of helium-3 is insensitive to many experimental factors.
See also
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International Temperature Scale of 1990
The International Temperature Scale of 1990 (ITS-90) is an equipment calibration standard specified by the International Committee of Weights and Measures (CIPM) for making measurements on the Kelvin and Celsius temperature scales. It is an appro ...
(ITS-90) — the calibration standard used for all temperatures above 0.6 K
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Leiden scale
References
Temperature
Scales of temperature
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