The present status of the standards of thermal radiation maintained by the Bureau of Standards

The Absolute Measurement of Radiant Power

“…Absolute thermopile. (Coblentz and Emerson, 1916) Based on its unfavorable assessment of absolute radiometers, the NBS proceeded to base its radiometric scale, first, on the radiant exitance of a blackbody according to the Stefan-Boltzmann law and, later, on the radiance of a blackbody as given by Planck's law (Coblentz and Stair, 1933;Kostkowski et al, 1970).…”

Effects of recent knowledge of atomic constants and of humidity on the calibrations of the National Bureau of Standards thermal-radiation standards

“…using thermopile 2028. of th e origlllal data should b e made on ~he basIs of tha t humidity. The data lll~s~r~ted In fig-ure 4 indicate that the range in hUDudltlCs ordmanly en- 3 'rhe distance at which the original siand ard lamps were calibrated, na mely, 20 Tn was n ot t be sa me as tbat used for the calibration of tbe detectors by t he b·lackbody. The latter' di sta nce varied from a bout 40 to 70 em.…”

“…No other type has been found to eq ual the carbon-filament lamp in ruggedn ess and stability, although many styles and types of lamps have been develop ed by industry through the years. A study was made both of lamps under carefully controlled laboratory conditions [3] and of a number of lamps re turned after years of service in various laboratories. This study established that these standards retain their original calibration with no significant change for more than 200 hours if not mechanically or electrically abused.…”

Photoelectric spectroradiometry and its application to the measurement of fluorescent lamps

“…At this Bureau all work of this type is n ecessarily r eferred to a fundamen tal black body. In practice, however, th ermal standards [5] that have b een prepared in the form of carbon filament lamps are employed. In th e presen t work secondary s tandards in the form of a special tungsten-in-qu ar tz lamp [6] and a quartz mercury-ar c lamp [7] are r equired to obtain a precise calibration of t he sp.ectrometer for use with a continuou s source havmg sup erimposed bright lines.…”

“…First, the absolute intensity of wavelength 365.5 m,u is determined by the thermopile and galvanometer through the use of the Corning filter G 5860, and a standard of thermal radiation [5]. (See table 1).…”