John M. Steele
Wed, 01 Sep 2010 12:41:18 -0700
I vaguely remember an old convention of degrees Celsius for temperatures and Celsius degrees for temperature differences; however, it is not documented anywhere (anymore?). Resolution 3 of 13th CGPM seems to clearly say the kelvin is used for BOTH temperature and temperature difference, there is no degree Kelvin. The degree Celsius is also used for both temperature and temperature differences.
There is a fuzzy reference to some prior decisions being abrogated (Res 7, 9th CPGM, Res 12, 11th CGPM, and 1962 CIPM, but usages resulting from those decions being "temprorarily OK." The abrogated decisions are not in the SI Brochure, so they may be this obsolete practice. (Without access to the former decisions, it is quite unclear.) ________________________________ From: "mech...@illinois.edu" <mech...@illinois.edu> To: U.S. Metric Association <usma@colostate.edu> Sent: Wed, September 1, 2010 3:16:57 PM Subject: [USMA:48448] Re: kelvin For temperature differences, "kelvin degree(s)" and "Celsius degree(s)" are equally acceptable in contrast with *positions* on a temperature scale with respect to conventional points of reference. e.g. absolute zero, freezing point of water, triple point of water, boiling point of water (at a specified pressure). ---- Original message ---- >Date: Wed, 1 Sep 2010 11:42:29 -0700 (PDT) >From: "John M. Steele" <jmsteele9...@sbcglobal.net> >Subject: [USMA:48443] Re: kelvin >To: "U.S. Metric Association" <usma@colostate.edu> >... > The one thing we should consider is in a compound > unit such as themal resistance, that depend on > temperature difference, only kelvins be used, or > for increments, 30°C is 5 K warmer than 25 °C.