Esmaspäeval, 10. novembril 2014. kell 16.15 toimub Physicumis Ravila 14C 3. korruse seminariruumis D312
Väike materjalifüüsika ja spektroskoopia seminar nr. 184
Martin Vilbaste, doktorant, Füüsika Instituut, TÜ
“Mõõtemääramatuse allikad ja analüüsimeetodid SI õhuniiskuse ühikute realiseerimisel Eestis” (doktoritöö materjalid)
“Uncertainty sources and analysis methods in realizing SI units of air humidity in Estonia”.
Air humidity is an important quantity that affects human comfort, properties of materials and is an important parameter in weather forecasting. Hygrometers that are used for air humidity measurement should be calibrated with respect to air humidity standards if it is necessary to ensure that the measured values are traceable to SI units.
Estonian air humidity reference standard that is based on a chilled mirror hygrometer in a climatic chamber has been developed since 2004 when EU supported Estonia to set up the standard.
Three measurement uncertainty estimation methods have been used for calculating the expanded uncertainties for the relative humidity reference values. The good agreement between the results indicates that the traditional GUM method is sufficient for this measurement equation.
In order to check the stability of the chilled mirror hygrometer´s dew-point temperature readings a simplified dew-point generator has been constructed and its performance has been tested. This dew-point generator works in a limited dew-point temperature range.
The significance of water contamination in the saturator vessel of a humidity generator has been studied as an additional uncertainty source. The results show that this uncertainty component is small compared to the combined standard uncertainty of dew-point temperature generation in the most accurate humidity generators operating nowadays.
At MIKES the effect of leaks in the tubing on the frost-point temperature of very dry air flowing in the tubing was studied experimentally and theoretically. The results of the study show that maintaining positive gauge pressure in the tubing effectively prevents ambient water molecules from back-diffusing through intentionally made circular holes in the wall of the tubing. Slightly released VCR connectors were found to be more susceptible to water-vapour back-diffusion into the tubing compared to Swagelok connectors.