Uncertainty determination in high-temperature spectral emissivity measurement method of coatings

•Analysis of uncertainty of emissivity measurement method for thick coatings.•Detailed identification of sources of uncertainty.•Precision and applicability of the method identified.•Original analysis approach can be beneficial to other emissivity measurement systems. The paper deals with uncertainty analyses of the new laboratory method for the measurement of spectral emissivity of high-temperature coatings. These coatings are intended to increase heat transfer in various industrial applications. The experimental set-up of the method is shortly introduced. The method is innovative in the application of scanning laser heating and in the coating surface temperature measurement using an infrared camera with a reference coating. Methods for total and partial uncertainty evaluation are described. As the uncertainty is always related to individual sample being measured, the DupliColor 800°C paint (MOTIP Dupli Ltd.) is used as an example to introduce the results. Except the absorption bands the uncertainty is below 4% with coverage factor k=2. Uncertainty spectral and temperature dependences are analyzed. Contribution of individual uncertainty sources as measured sample signal, measured laboratory blackbody signal, sample surface temperature, laboratory blackbody temperature, surroundings temperature, blackbody effective emissivity and surroundings emissivity and their sub-components are discussed.