The facilities of the Metrology Research Institute at the Helsinki Universi
ty of Technology, and methods for characterisation of optical detectors for
spectral radiant intensity and irradiance responsivity, are described. The
instrumentation for such characterisations includes a reference spectromet
er with a number of auxiliary set-ups, and equipment for the spectral irrad
iance measurements with a filter radiometer based on a trap detector. The m
ethods of realising the spectral responsivity scales based on an absolute c
ryogenic radiometer in house are addressed. The procedures and results of c
haracterisation of a multipoint measuring system of photosynthetically acti
ve radiation, by employing the available facilities, are briefly described.
The absolute irradiance responsivity of the device is determined by using
a photometric lamp, whose spectral irradiance has been measured with the fi
lter radiometer. The combined standard uncertainty of this set of calibrati
ons is 3.6% at the 1 sigma level. The uncertainty is caused almost complete
ly by the multipoint measuring system. (C) 1999 Elsevier Science B.V. All r
ights reserved.