A comparison of temperature scale near fixed points in the low temperature range.

Project Description

A capsule type thermometer will be calibrated at (near) fixed points, in the low temperature range, at BNM-INM and at INTiBS and the results will be compared.

Final Report 2011-03-20

A capsule type thermometer was calibrated at (near) fixed points, in the low temperature range, at BNM-INM and at INTiBS. Because INTiBs is intending to make a comparison with NRC in the continuity of the K2 key comparison (following a  protocol similar to the one adopted for the K2 key comparison), the results obtained during the EUROMET project will not be communicated to the partners before the comparison will be finished.In the frame of CCT-K2-4, two thermometers (from INTiBs) were calibrated at NRC in 2005 and were brought to INM at the end of 2005. The calibrations are finished at INM. INM sent the thermometers to  INTiBs and the results to NRC in 2006.At INTiBS the thermometers were measured in the water triple point. For the measurements a new water cell with an isotopic composition certificate was used. Resistance of the thermometers was measured with F18 and MI6015 bridges to compare results given by AC and DC techniques. In 2006 a new apparatus for realization of the mercury triple point – cell and bath – was bought by INTiBS. During 2 month testing of the bath, a leak of the cooling substance was stated and the bath was sent back to the producer. After reparation, the measurements at the triple point of mercury will be done.The both thermometers were calibrated at  the of oxygen triple point.In 2007 at INTiBS the two CSPRTs  resistances were measured at all low temperature fixed points - the triple point of hydrogen, neon, oxygen, argon, mercury and water. For the both thermometer, the values of the constants of the interpolating equation according to the ITS-90 were estimated. Because in that period a damage of a mercury cell used for calibration of the thermometers was noticed, INTiBS decided to repeat the resistance measurements at the mercury triple point after repearing of the mercury cell by its producer. The cell was sent back to the INTiBS in March 2008.

In 2008 two CSPRT were measured at INTiBS in the mercury triple point cell no Hg 220 and resistance of these thermometers were checked at the water  triple point. After the mesurements a report contained calibration data for the thermometers (values of function W at the triple point of hydrogen, neon, oxygen, argon and hydrogen and the resistance at the triple point of water) was prepared at INTiBS and sent to CNR in the middle of 2008.

CNR has prepared the final report of the CCT-K2.4 key comparison and sent it the CCT WG8

Thermometry (T)
Dr Yves Hermier, LNE-INM (France)
Coordinating Institute
Participating Partners
INTiBS (Poland)