| Popis: |
Over the past decade, several studieshave verified the long-term stability ofthese radiometers. However, while they output a singlenumber, their spectral, angular and absolute characterization remains technically challenging.Traditionally, NIST-traceable FEL spectral irradiance standard lamps are used to characterizenarrowband, mechanically scanning TJV monochromators with PMT detectors. Once characterizedin terms of absolute response it is placed outdoors next to a broadband UV-B radiometer andoperated under clear sky conditions over a day. The measured spectral inadiance from themonochromator is weighted against the measured spectral response ofthe UV-B pyranometer undertest and integrated over the 280-400 nm range (or the range of the monochromator), for eachmeasurement time. This weighted integral is then plotted against the voltage output of thebroadband radiometer, where the slope ofthe plot is the radiometer's transfer function.There are several limitations with this technique. No physically realizable optical detector exhibits aperfect Lambertian angular response. Due to solar elevation changes throughout the day, variationsin the cosine response of both the broadband radiometer (device under test) and thespectroradiometer are necessarily averaged. Moreover, because typical field scanningmonochromators require anywhere from 5 to |
