Evaluation of spectral irradiance transfer standards

The performance of spectral irradiance transfer-standard lamps has long been a concern in the radiometry and photometry communities. The adoption of a modified FEL-type lamp has recently been proposed as the most suitable transfer standard for spectral irradiance measurements. While data have been published on the performance of these lamps when operated continuously and in a laboratory environment, however, little information is available on their performance under typical usage. The results are presented of "real-life" testing of over thirty FEL lamps both pre-selected, according to published procedures, and direct from the manufacturer. When operated vertically all of the lamps tested suffered terminal coil collapse after between 140 h and 250 h burn time. The reproducibility of the FEL lamps after transportation is also investigated.