Results of a training exercise in the comparison and calibration of pyranometers and pyrheliometers

An intercomparison and calibration exercise was conducted. The exercise involved applying classical comparison and calibration techniques to pyranometers and pyrheliometers. As well as demonstrating the techniques for acquiring and reducing calibration data, analysis of the data indicates the relative performance of the instruments tested and the effects of the radiation distribution and meteorological parameters on the calibration. Variability in calibration results within a day amounted to + or - 5.0% and was repeatable from day to day within about + or - 2.0%. The solar evaluation angles were between 35 and 68 deg, and the diffuse to global radiation ratio was on the order of 20%.