|
 |
 |
 |
View Paper |
Session Topic: 5B, Temperature Session |
|
|
Paper Title: An Optimal Gallium Cell - Interoperably Between a Cell Made in England and Intercompared at NIST, to Its Reference Cell |
|
|
Date & Time: TUESDAY, August 6, 2002 |
|
2:30 - 4:00pm PARALLEL SESSIONS - SESSION 5 |
|
|
Speaker: John P. Tavener
Isothermal Technology Ltd. |
Email: info@isotech.co.uk |
|
|
In 1996 the CCT published a document called Optimal Realizations of ITS-90. This was revised in 2000 (ref. CCT/2000-13). In it, and for the first time it states that the Gallium Fixed Point… must not be sealed… each cell must be equipped with a valve… so that the gas over the metal can be controlled and its pressure measured. At the Northern Temperature Primary Laboratory (NTPL) the Gallium Cell is sealed. It was therefore decided to modify the cell (which contains Gallium certified 8N pure) by passing the seal with a hollow copper capillary tube. The cell could then be vacuumed and back-filled to 1 atmosphere of pure Argon. The Cell was melted a number of times. The complete melt being recorded. It was then sent, with its apparatus to NIST in America for intercomparison with their reference cell. NIST was chosen because it has done most research into the Gallium Point and in consequence has the smallest uncertainties of realization. The flatness of the melt confirmed that the purity of the metal had been maintained, and the absolute value of the Cell made in England agreed within 2mK of the NIST reference. 2 sigma uncertainties of the intercomparison were ±20mK. The results illustrate the close agreement of internationally produced Gallium Cells made to CCT/2000-13. |
|
 |
 |
|
NCSL International © 1996-2002 All Content. 1800 30th Street, Suite 305, Boulder, Colorado 80301-1026
Tel: (303) 440-3339 Fax: (303) 440-3384 info@ncsli.orgCD-ROM produced by X-CD Business Solutions |
|