Use of Regression Analysis to Estimate Uv Spectral Irradiance From Broad Band Radiometer Readings Under Fs‐40 Fluorescent Sunlamps Filtered With Cellulose Acetate

Weighted and unweighted UV spectral irradiances were measured under a 2‐lamp fluorescent fixture containing Westinghouse FS‐40 fluorescent sunlamps filtered with (6 h aged) 0.127 mm (0.005 in.) cellulose acetate by use of newly developed broadband UV radiometers and an automated UV spectro‐radiometer. Measurements were taken at 10‐cm intervals between 20 and 110 cm from the lamps. Correlations were determined between sets of data measured with the broadband radiometers and the UV spectroradiometer. By use of linear regression analyses on the weighted and unweighted spectral data, regression equations were developed for predicting UV‐B irradiance (unweighted mWm‐ 2 ), biologically effective UV (BUV) (weighted mWm) in the 280–320 nm (UV‐B) region, UV‐B sun equivalents, and incident flux density in the UV‐B region in photons m‐ 2 × 10 21 integrated over a 6‐h exposure. Examination of the correlation coefficients ( r values) indicated that agreement was excellent between measured and predicted values for all comparisons (r values from 0.9972 to 0.9998). Use of regression equations should permit accurate. rapid estimation of both weighted and unweighted UV irradiances at any location in an experimental set‐up and provide a useful means for intra‐ and inter‐laboratory comparisons of spectral measurements, made in the interagency BACER program under FS‐40 fluorescent sunlamps filtered with 0.127 mm cellulose acetate (aged for 6h).