The National Institute of Standards and Technology (NIST) has developed a new acoustic thermometer that measures temperature with unprecedented accuracy between 0°C and 552°C. This device determines thermodynamic temperature by measuring the speed of sound in argon gas, and its measurements are five times more accurate than the 1990 benchmark values.
The NIST acoustic thermometer improves the accuracy of platinum resistance thermometry, which is currently used to disseminate accurate temperature standards. By measuring the ratio of acoustic resonance frequencies in a nearly spherical cavity of argon gas and accounting for thermal expansion using microwave resonance frequencies, the device achieves a five-fold reduction in uncertainty for thermodynamic temperature in the range of 273 K to 552 K.
The International Temperature Scale of 1990 (ITS-90) approximates thermodynamic temperature but is constructed from inconsistent constant volume gas thermometry data. The NIST acoustic thermometer provides a more accurate alternative to ITS-90, with excellent agreement between its measurements and other temperature measurement methods.
Source: https://www.nist.gov/programs-projects/acoustic-thermometry
Keywords: NIST Acoustic Thermometer, Thermodynamic Temperature, Temperature Scale
