A selective Pt-CdS photodiode to monitor erythemal flux

The design and potential benefit of a solar ultraviolet (UV) radiometer rep orting a maximum instantaneous flux of erythemally weighted heterogeneous e nergy is considered. The proposed device is electronically peak detecting; the user would ideally 'point and paint' the sun to fmd a localized maximum . A projected exposure time can be calculated from an instantaneous reading of erythemally weighted flux for a given minimal erythemal dose (MED) spec ified by the user. This calculation, though not necessarily providing a tru e exposure time, may be useful and informative in that it serves as a more 'recognizable' measure of erythemal flux and introduces a custom scale for each individual via their MED. Erythemal flux is calculated as the weighted integral sum integral j(lambda,t)epsilon(lambda)d lambda, where j(lambda,t ) is the instantaneous angular integrated spectral irradiance accepted by h uman skin. This instrument proposal uses a single interference filter over a Pt-CdS photodiode; the interference tilter is offered as a nominal design transmittance. The simulated response of the selective photodiode has a ne ar-linear relation to the effective irradiance. Test inputs for evaluation purposes and to elucidate a transducer response are constructed from a spli ne interpolation of the World Radiation Center (WRC) spectrum and classic t ransmittance models. Our desired erythemal flux is offered in interconverti ble UV Indexes (UVIs) as a function of zenith angle and atmosphere, charact erized by elevation, ozone path, and turbidity. (C) 1999 Elsevier Science S .A. All rights reserved.