UDC 535.247-15:681.785.6 © Slavko Pokorni ERROR ANALYSIS OF EMISSIVITY MEASUREMENT BY INFRARED SENSOR The mathematical model for the emissivity measurement based on infrared radiation is proposed. <...> Measurement error function is derived and analyzed. <...> The results of analysis are presented and measurement conditions for better measurement accuracy are determined. <...> INTRODUCTION To determine temperature of an object by infrared (IR) radiation one need to know the values of the emissivities of that object, which has great inf luence on measurement accuracy [1]. <...> Emissivity data can be found in a manual [4]. <...> Emissivity depends on a number of parameters of IR sensor such as wavelength range of radiation, and parameters of object such as temperature, angle of radiation, condition of surface [2]. <...> Because of that such data of emissivity are unreliable and can cause a significant error in temperature determination by an infrared instrument. <...> Emissivity of a given object can be determined by the same infrared instrument used for the temperature measurement of that object and in the same conditions concerning the infrared sensor and the object [1]. <...> The only difference is that we need to know or measure the surface temperature of the object. <...> In this paper we will derive and analyze equation for emissivity determination and equation for emissivity measurement error by infrared sensor based on work in [1]. 2. <...> EMISSIVITY MEASUREMENT EQUATION Electrical signal (thermal value) at the output of IR detector is given by relation [1] , (1) where 1, 2 perature T; Io – calibrated thermal value for T=To object temperature); Ia T=Ta (Ta ty of IR detector; Ie object surrounding; – atmospheric transmission. <...> ERROR ANALYSIS For quantitative analysis of measurement error we choose input data given in table 1. <...> Table 1 where actual relation between blackbody temperature and instrument output signal (thermal values), is determined through the process of IR system calibration, and for AGEMA Thermovision 870 camera is [3] , (4) where R, B, F are calibration constants which depends on selected scanner, lens, filter and aperture. 3. <...> EMISSIVITY MEASUREMENT ERROR EQUATION On the base of relation (3) and relation where xj (j = 1, ., 6 <...>