An International Intercomparison of Spectral Irradiance Scales

An intercomparison among the spectral irradiance scales of eight national standardizing laboratories has been carried out by the Electrotechnical Laboratory of Japan. Four tungsten-filament, quartz-bromine lamps with clear of frosted bulbs were distributed to each of the participants. The values of spectral irradiance, produced by the lamps at a specified point were measured at seven wavelengths from 300 to 800 nm. The comparison shows that most of the laboratories agreed within ±1%, except for the wavelengths of 300, 350 and 800 nm. It is suggested that further study is necessary at those wavelengths.