Accurate assessment of f1′ value of fine photometer heads

Abstract

For an accurate assessment of the f′1 value of a photometer head it is important to determine the maximum step size for sampling and an appropriate bandwidth of the monochromator for an acceptable uncertainty contribution. A simulation is carried out to evaluate these uncertainty contributions for fine photometer heads, with a mismatch characteristic f′ ⩽ 3% and uncertainty contributions f′ ⩽ 0.1 % taken as the limits for acceptance. Assuming a stable measurement set-up, the results show that a 5 nm step size and a 5 nm bandwidth or less are needed for this assessment. The uncertainty of the f′1 value caused by the wavelength uncertainty of the monochromator is analysed additionally. For extended bandwidths a method is proposed to correct the spectral responsivity data of the photometer head and reduce the bandpass uncertainty contribution effectively.