Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.




Michael R. Moldover, Roberto M. Gavioso, James B. Mehl, Laurent Pitre, Michael de Podesta, Jintao Zhang


We review the principles, techniques and results from primary acoustic gas thermometry (AGT). Since the establishment of ITS-90, the International Temperature Scale of 1990, spherical and quasi-spherical cavity resonators have been used to realize primary AGT in the temperature range 7 K to 552 K. Throughout the sub-range 90 K 90). (Here T is the thermodynamic temperature and T90 is the temperature on ITS-90.) With a minor exception, the resulting values of (T - T90) are mutually consistent within 3 ×10-1 T . These consistent measurements were obtained using helium and argon as thermometric gases inside cavities that had radii ranging from 40mm to 90 mm and that had walls made of copper or aluminium or stainless steel. The AGT values of (T - T90) fall on a smooth curve that is outside {+or-}u(T90), the estimated uncertainty of T90. Thus, the AGT results imply that ITS-90 has errors that could be reduced in a future temperature scale. Recently developed techniques imply that low-uncertainty AGT can be realized at temperatures up to 1350 K or higher and also at temperatures in the liquid-helium range.


acoustic resonators, acoustic thermometry, gas thermometry, primary thermometry, microwave resonators


Moldover, M. , Gavioso, R. , Mehl, J. , Pitre, L. , de, M. and Zhang, J. (2014), ACOUSTIC GAS THERMOMETRY, Metrologia, [online], (Accessed May 24, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created January 16, 2014, Updated February 19, 2017