Uncertainties in the determination of thermal emissivity by measurement of reflectance using Fourier transform spectrometers

• Published in: Thin solid films Vol. 502; no. 1; pp. 164 - 169
• Main Authors: van Nijnatten, P.A., Hutchins, M.G., Kilbey, N.B., Roos, A., Gelin, K., Geotti-Bianchini, F., Polato, P., Anderson, C., Olive, F., Köhl, M., Spragg, R., Turner, P.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Lausanne Elsevier B.V 28.04.2006; Elsevier Science
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Emissivity; Exact sciences and technology; Fourier transform spectrometers; Fundamental areas of phenomenology (including applications); Measurement intercomparison; Metals, semimetals, and alloys; Optical coatings; Optical elements, devices, and systems; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optics; Physics; Reflectance; Visible and ultraviolet spectra; Measurement intercomparison; Emissivity; Fourier transform spectrometers; Reflectance; Gold; Inorganic compounds; Binary compounds; Infrared spectra; Experimental study; Tin oxides; Reflectivity; Silver; Transition elements; Thermal emissivity; Fourier transform spectra; Mirrors; Optical coatings
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2005.07.262

The emissivity of coated glazing is commonly determined from spectral reflectance measurements using a specular reflectance accessory or other suitable reflectance attachment. As part of the ongoing EU Thermes RTD project, a 19 laboratory intercomparison was undertaken in 2003 to establish the state-of-the-art of infrared reflectance measurement accuracy and uncertainty and to identify any needs for improvement. Six test samples were selected to provide samples with low, medium and high infrared reflectance. In addition, bare gold mirrors were prepared for distribution to each participant to serve as the reference material. Both the reference mirrors and the round robin samples were calibrated and evaluated prior to delivery to enable closely characterised and similar sample sets to be prepared. A measurement procedure requiring a sequence of 18 measurements undertaken in a strict order was developed. The outcome of the exercise is very encouraging. Participants have performed the work using a wide range of experimental conditions but the final results are in excellent agreement. This is because of the adherence to the required measurement procedure and the use of reference mirrors with known reflectance values. The analysis indicates uncertainties in the final results which are less than ± 0.01. Factors such as instrument resolution, number of scans and time of acquisition do not appear to have been significant in affecting measurement accuracy.