The wavelength coefficient of radiance temperature of tungsten-strip lamps of the High-Stability type was experimentally determined at the silver point. To do this, a set of eight lamps were calibrated at 620 nm, 650 nm and 680 nm. A mean value of the wavelength coefficient dt_(λ)/dλ=0.1144°C/nm was obtained. This experimental value differs by 3% from calculated values. Accounting for the spread shown by the various lamps, it was estimated that the measured coefficient should be applicable to all lamps of the same type with an uncertainty of 3% at the 95% confidence level.
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