Extrapolation scheme for long stem thermometers range calibration down to 77K

Project Description

Laboratories point out the need to calibrate long stem thermometers down to liquid nitrogen temperature. For accurate measurements, the nitrogen vapor pressure measurement is not convenient to reach the true temperature in the bath where the calibration has to be done. A "simple" way is to use a capsule type thermometer calibrated down to the oxygen point to measure the temperature.
Nevertheless, for a lot of applications, an extrapolation of the long stem thermometer calibration data should be enough. But the linked error and the associated uncertainty have to be studied.

UME and LNE propose to set up this point, using capsule type thermometers calibrated at LNE-INM.

Final Report 2012-04-06

Laboratories point out the need to calibrate long stem thermometers down to liquid nitrogen temperature. For accurate measurements, the nitrogen vapor pressure measurement is not convenient to reach the true temperature in the bath where the calibration has to be done. A "simple" way is to use a capsule type thermometer calibrated down to the oxygen point to measure the temperature.
Nevertheless, for a lot of applications, an extrapolation of the long stem thermometer calibration data should be enough. But the linked error and the associated uncertainty have to be studied.
Results concerning this issue were presented by different partners (in this project and outside) as CCT working documents, at the CCT 2010 session.A guide was written by NPL, in collaboration with TC-T members (in particular the members of the working group "best practices") and submitted for adoption to the TC-T.