The main problems when measuring surface temperature by means of radiometry (i.e., optical pyrometry) are the unknown emissivity and radiation reflected by the sample. The latter problem becomes critical when the sample is placed in hot surroundings, such as furnaces or combustion chambers; indeed, the reflected flux may then become larger than the emitted flux. In this paper we describe a novel technique, based on the photothermal effect, which allows the surface temperature to be measured without error due to reflected fluxes. The influence of the parameters of the experimental setup are discussed. Experimental data obtained with a sample placed inside a furnace are reported in the (300-1150 K) range. The experimental results show the efficiency of the technique which proves to be a general solution to extend the domain of application of optical pyrometry.
2014 Cet article est consacré à une revue synthétique des méthodes de mesure des propriétés radiatives des matériaux opaques. Après un rappel des différents paramètres radiatifs que l'on peut avoir à connaître et des relations permettant la détermination indirecte de certains d'entre eux, on donne une description critique et comparative de leurs principales techniques d'obtention. La démarche adoptée commence par l'examen des méthodes de mesure du paramètre radiatif le plus fin et peut-être le plus délicat à mesurer 2014 la réflectivité bidirectionnelle monochromatique 2014 et s'achève sur les paramètres les plus grossiers, à savoir les facteurs totaux hémisphériques, en passant par les différents facteurs intégrés sur l'espace ou la longueur d'onde. Un accent particulier est mis sur certaines causes d'erreur communes à la plupart des montages décrits, en particulier celles dues aux phénomènes de polarisation. Un moyen de s'en affranchir est indiqué.Abstract 2014 This paper reviews the experimental techniques used in measuring the thermal radiation properties of opaque materials. After a survey of the different radiation parameters and the relations allowing reciprocal determination of some of them, a critical description of the main measurement techniques is made. The review extends from examining the methods of measuring spectral bidirectional reflectance, from which all other radiation parameters can be theoretically derived, to methods used for total hemispherical parameters. An emphasis is made on experimental error problems, specially those involved with polarization phenomena. Some means of avoiding these errors are suggested.
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