Every temperature sensor requires calibration against a more accurate standard. But how do we know that the standard is correct? In the end we require a calibration against a primary thermometer, a device which infers the temperature from knowledge of basic physics.
At NPL we have recently built the most accurate primary thermometer in history which has revealed with unprecedented resolution the (small) errors in every other thermometer on Earth. The device is based around a spherical acoustic resonator, and infers the temperature from precision measurements of the speed of sound in argon.
In this talk I will describe how the device works and make a primary temperature measurement (live!) using a 3-D printed replica. Finally I will discuss the opportunities for exploiting acoustic phenomena in a wider range of sensor applications.
Michael de Podesta
National Physical Laboratory
Michael de Podesta (56) graduated with a BSc in Physics from Sussex University in 1981 and then in 1985 completed a DPhil in the electronic properties of metals at cryogenic temperatures. After postdoctoral work at Bristol University, he was appointed a lecturer at the University of London in 1987, and joined NPL in 2000, working mainly on problems related to temperature measurement. In 2013 he led the team which published the lowest uncertainty estimate of the Boltzmann constant and in 2015 published the most accurate thermometry in human history.
Michael is a chartered physicist, a member of the Institute of Physics, and in 2009 was awarded an MBE for services to Science.