Vol. 116, Issue 5, May 2010, pp. 122-130

Stability of High Temperature Standard Platinum Resistance Thermometers at High Temperatures

Y. A. ABDELAZIZ and F. M. MEGAHED

National Institute for Standards (NIS), Giza, Egypt

Tel.: ++202 010 5790 620, fax: ++202 33867451

E-mail: yasserabdelfatah@yahoo.com

Received: 29 March 2010   /Accepted: 24 May 2010   /Published: 31 May 2010

Abstract: An investigation of the stability of high temperature standard platinum resistance thermometers HTSPRTs has been carried out for two different designs thermometers (with nominal resistance 0.25 Ω and 2.5 Ω) from two different suppliers. The thermometers were heated for more than 160 hours at temperatures above 960 ⁰C using a vertical furnace with a ceramic block. A study was made of the influence of the heat treatment on the stability of the resistance at the triple point of water, and on the relative resistance W_(Ga) at the melting point of gallium.

The thermometers showed a correlation between the drift note and the values of W_(Ga). It was found also that the HTSPRT which has a sensor with strip shaped support and low nominal resistance is more stable than the HTSPRT which has a sensor in the form of a coil wound on silica cross. The 0.25 Ω thermometer has better stability @ 7x10^{-6 0}C (at TPW) after 40 hour. Factors affecting the stability and accuracy of HTSPRT also will be discussed.

Keywords: HTSPRT, Melting point of gallium, Triple point of water

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