The suitability of tungsten strip lamps as secondary standard sources in photoelectric pyrometry

It is shown that the tungsten strip lamp is satisfactory for use as a secondary standard of temperature measurement in realizing the International Practical Temperature Scale above 1063° C with a photoelectric pyrometer. The errors of calculation due to uncertainties in the tungsten emissivity and transmittance of the lamp window are 0.01 degC at 1063° C and 0.03 degC at 2000° C. Typical curves are given for the variation of luminance temperature with position along the strip and with angle of view. The reproducibility of tungsten strip lamps is ±0.05 degC for vacuum lamps at 1063° C and ±0.10 degC for gas-filled lamps at 1400° C. The long term stability of the best lamps tested was a decrease in luminance temperature of 0.2 degC per 100 hours for a vacuum lamp at 1400° C and 0.3 degC per 100 hours for a gas-filled lamp at 2000° C.