Some Studies to Establish the Standard of Thermal Radiation Using a Large Black-body Furnace

In order to establish the reliable standard of thermal radiation, a black-body furnace of a large size was constructed in our laboratory. The dimensions of the furnace are as follow; a, aperture of the standard window 3cm b, inner diameter of the black-body 10cm c, inner length of the black-body 52cm d, outer diameter of the furnace 46cm e, length of the furnace 100cm Accuracy of the measurement has been improved remarkably, as the radiation was intensified, so that the following facts were proved by experiments. (1) Compensating the effect of absorption by the water vapour in atmosphere, we have become to abtain the constant value for the sensibility of any thermopile at any distance from the standard window of the black-body. (2) As our former report generally the sensibility of the thermopile changes slightly, according to the color-temperature of the black-body. When the window material such as mica, quartz, fluorite or glass were used, or when the metallic reflector were used, the change of the sensibility would be remarkable further more. (3) Considering the above problems, calibrations of the thermopile have been performed successfully by our black-body furnace, and their results are almost agreeable to that which were obtained by the another experiment using the standard lamps which were calibrated by the N, B, S.