Spectral irradiance comparison using a multi-wavelength filter radiometer

An automatic multi-wavelength filter radiometer (MWFR) was developed at the National Metrology Centre (NMC) of Singapore to realize the spectral irradiance scale in the wavelength range from 250 nm to 1600 nm. The UV-VIS range (250 nm to 900 nm) is covered by a silicon trap detector with 17 filters, while the near IR range (900 nm to 1600 nm) is covered by an InGaAs photodiode with 7 filters. A complete run of measurements at all 24 wavelength points takes only 12 min. The spectral irradiance scales of NMC and MIKES/TKK (Finland) in the spectral range from 280 nm to 900 nm were compared successfully using this instrument. Measurement results of three standard lamps calculated using MIKES/TKK's algorithm showed excellent repeatability and very good agreement with their assigned values. It is concluded that, compared with the conventional monochromator based spectroradiometers, a properly designed MWFR with sufficient spectral coverage is a good alternative instrument for spectral irradiance comparison owing to its faster speed and better short-term reproducibility.