Calibration factor chosen such, that the ASTM AM 1.5 reference spectrum with 1000 W/m² global irradiance (http://lamps.licht-im-terrarium.de/spectrummeasurements/view/1) results in a meter reading of 1000 W/m². This is based on the description on the solarmeter website: "The master meter was calibrated to match standard class II pyranometer on a plane tilted 37° from horizontal, oriented perpendicular to the axis of the sun, under airmass 1.5 global solar irradiance at an independent test lab"
Spektral sensitivity adapted to match experiments