Illuminance responsivity calibration of reference photometers at the NIST SIRCUS and SCF facilities
George P. Eppeldauer, Carl C. Miller, Thomas C. Larason, Yoshihiro Ohno
The illuminance responsivities of two transfer standard photometers have been directly determined from their spectral responsivity calibrations at two different calibration facilities of NIST. The main characteristics of the two photometers, and their calibrations are described. The spectral and broad-band (illuminance) responsivities measured at the two different facilities are compared. The two different illuminance responsivity determinations on both photometers agreed within 0.1 % with an overall uncertainty of 0.2 % (k=2). A new photometric scale derivation scheme is also discussed.