Acoustic measurements of the thermodynamic temperature between the triple point of mercury and 380 K

Abstract

We have measured the differences between the Kelvin thermodynamic
\ntemperature and the temperature of the International Temperature Scale of
\n1990 on nine isotherms between the triple point of mercury and 380 K, by
\nmeans of a primary acoustic thermometer. For the present measurements the
\nstandard uncertainty of (T − T90) ranges from 0.9mK at 234K to 1.7mK at
\n380 K. The experimental method is based on the measurement of the
\nacoustic resonance frequencies of an argon-filled spherical cavity and the
\nmicrowave resonance frequencies of the same cavity when evacuated. The
\npresent results agree within the remarkably small combined uncertainties
\nwith both NIST acoustic thermometry ([1] Moldover M R et al 1999 J. Res.
\nNatl Inst. Stand. Technol. 104 11–46; [2] Strouse G F et al 2002 Progress in
\nprimary acoustic thermometry at NIST: 273K to 505K 8th Temperature
\nSymp. (Chicago, 21–24 October 2002)) and UCL acoustic thermometry
\n([3] Ewing M B and Trusler J P M 2000 J. Chem. Thermodyn. 32 1229–55)
\nin the overlapping temperature range.