Uncertainty Estimations for Standard Humidity Generator of INTI

Abstract

Two methods for the uncertainty estimation in the dew/frost-point temperature and relative humidity are shown. The uncertainty estimation was performed propagating the uncertainties of pressure and temperature measurements in the corresponding equations in the classic method, and propagating the distributions of the input variables, pressure and temperature, (Monte Carlo simulation) in an alternative method. The results obtained by the different methods are compared for analyzing the validity of the uncertainty calculations, and the assumption of negligible correlations between the input variables. The agreement between the presented uncertainty analysis and the outcomes of the comparison with INMETRO is discussed. List of symbolsrh Relative humidity t dew Dew-point temperature t frost Frost-point temperature e w (t) Vapor pressure f (t, P) Enhancement factor P s Total pressure in saturator P c Total pressure in test chamber t s Temperature in saturator t c Temperature in test chamber 123 Int J Thermophys u(rh) Standard uncertainty in relative humidity u(t dew ) Standard uncertainty in dew-point temperature u(t frost ) Standard uncertainty in frost-point temperature u(e w ) Standard uncertainty in vapor pressure equation u( f ) Standard uncertainty in enhancement factor equation u(P s ) Standard uncertainty of saturation pressure measurement u(P c )Standard uncertainty of chamber pressure measurement u(t s ) Standard uncertainty of saturation temperature measurement u(t c )Standard uncertainty of chamber temperature measurement