feedback from Patrick Rourke (CCT) re quantity "Celsius temperature"

[jmilesBIPM]

Extracted from email from Patrick Rourke (9 December 2024):

The ITS-90 kinds of quantity are “ITS-90 temperature (℃)” and “ITS-90 temperature (K)”, whereas the thermodynamic temperature kinds of quantity are “thermodynamic temperature” (for the K version) and “Celsius temperature” (for the ℃ version). In my opinion, these would be easier for users to understand if they were written as “thermodynamic temperature (K)” and “thermodynamic temperature (℃)”: parallel construction to the ITS-90 quantities and matching how people actually use the quantities. However, https://preprod.si-digital-framework.org/SI/units/kelvin specifically says “Celsius temperature” so I’m not sure if we can go against that. Thoughts?

From Janet: I suggest we include the proposed label “thermodynamic temperature (℃)” as requested, using skos:"altLabel" for "Celsius temperature". NB This would have to be confirmed with: Patrick Rourke, Dolores Del Campo and Richard Brown.

[Crparedes]

Further discussions with Patrick Rourke led to the following request:

• Simplify from four to two quantities:
  • “ITS-90 temperature (℃)” and “ITS-90 temperature (K)” become simply "ITS-90 temperature", which can be expressed in kelvins (default), but the CMCs with that quantity in the service categories will also accept degrees Celsius
  • “thermodynamic temperature” and “Celsius temperature” become simply "thermodynamic temperature", which can be expressed in kelvins (default), but the CMCs with that quantity in the service categories will also accept degrees Celsius
• define the new quantity for temperature difference, expressed by default in kelvins, but where $1~\mathrm{K} = 1~\mathrm{^{o}C}$

[Crparedes]

According to https://doi.org/10.1063/5.0235453, by @BlairDHall et.al., and as discussed with @fmeynadier and @Prourke, three different quantities should be defined for temperature differences measured thermodynamically, in the ITS-90 scale, or the PLTS-2000 scale.