Portable detector-based primary scale of spectral irradiance

A method developed at the Helsinki University of Technology (HUT) for calib rating standard lamps of spectral irradiance in UV-A and UV-B regions is pr esented. The method is based on a compact filter radiometer that is charact erized absolutely to measure spectral irradiance. The filter radiometer can be brought to laboratories where accurate calibrations are needed. The met hod overcomes some of the instability problems encountered when using lamps as transfer standards, which makes it also useful in intercomparison campa igns. Test measurements are presented where two standard lamps issued by th e National Institute of Standards and Technology (NIST), USA, are compared with the HUT scale held by the radiometer. The results suggest that the agr eement between the two scales (HUT and NIST) is approximately 1% - 2% in th e wavelength region from 300 nm to 400 nm.