2005 Realisation of the Australian candela

摘要

The luminous intensity unit, the candela, was last realised in Australia in 1997. International comparisons in CCPR-K3b and APMP.PR-K3b (1997 - 2000) showed excellent agreement between the unit obtained and the world mean value for the candela. However, due to the nature of the working standard lamps on which the unit is maintained, the realisation of the candela must be performed on a regular basis to determine the possible drift in the working standards. Improvements in source stability, the measurement of aperture area and techniques in spectral responsivity calibration since 1997, result in NMI's present ability to realise the candela with reduced uncertainty. In this approach we use a source consisting of a super stable mercury-xenon lamp with interference filters, a precision aperture calibrated using a coordinate measuring machine and a refined spectral responsivity measurement to more accurately determine the spectral responsivity of the reference photometer. The results of the measurements are presented.