Browsing by Author "Nicoletti, Fabiano"

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    Interlaboratory comparison of solar range transmittance and reflectance of coated and uncoated flat glass
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1994) Nicoletti, Fabiano; Polato, Pietro; Roucour, Jean
    Transmittance and reflectance measurements on glass for architectural applications using commercial spectrophotometers may be affected by errors resulting from an improperly operated instrument, an inappropriate calibration, etc. Discrepancies between the values of parameters such as light reflectance and solar factor measured on the same glass product by different laboratories can be very pronounced. In order to avoid disputes among glass producers and complaints from glass users the interlaboratory reproducibility and the accuracy of the measurements must be improved. A n intercomparison was organized by Technical Committee 10 "Optical Properties of Glass" of the International Commission on Glass among 15 laboratories and one metrological institute on transmittance and reflectance measurements on commercial coated and uncoated glasses. Good reproducibility and accuracy in transmittance measurements ( ± 0 . 6 %) have been achieved even with each laboratory using its own instrumental procedures. In the case of reflectance, a preliminary round robin performed using the same instruments gave very large discrepancies in the spectral and integrated values. Reproducibility and accuracy of the same order of magnitude as in the transmittance measurements were obtained when each laboratory used a standardized procedure and the same reference standards, the latter having optical characteristics similar to the samples.
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    Spectrophotometric determination of the normal emissivity of coated flat glass Report of the International Commission on Glass Technical Committee 10 "Optical Properties of Glass"
    (Offenbach : Verlag der Deutschen Glastechnischen Gesellschaft, 1988) Nicoletti, Fabiano; Geotti-Bianchini, Franco; Polato, Pietro
    The results of the activity of TC 10 of the International Commission on Glass aimed at assessing the reproducibility and accuracy of the determination of normal emissivity from IR reflectance measurements with commercial spectrophotometers are presented. Eight European and American flat glass producers and two glass institutes participate in the activity. Two intercomparisons of near normal spectral reflectance are performed on 4 samples, representative of the current production. The circulated samples are subsequently calibrated in a metrological laboratory. The results show that even with a free integration procedure and reference mirror a satisfactory reproducibility can be achieved (the maximum discrepancy in computed U values between the participants being within 0.1 W/(m2 K)). The agreement significantly improves by using a common reference mirror, showing the importance of the availability of reference mirrors calibrated by some metrological source. After discussing the effect of the integration procedure on the resulting emissivity, a new 30 selected ordinates method is developed and transmitted to ISO (to be incorporated into the standard for the computation of the U values of double glazings).