[werk_ag]

It seems very good, however if you want to slightly increase the readings to be even closer to Apogee Clear Sky Calculator, or other nearby Weather Stations, you can try changing the range in the code bellow. Start by increasing the 1600 value in steps of 40 units, and fine tune with lower steps. Preferably you should do it when the sun its at full noon.

Code:

       SolarRad = map(RX_Data[2], 0, 1023, 0, 1600);  

Looking to the graphs in your webpages, seems you are getting a very close match with the theoretical values. Always make sure the pyranometer is perfectly horizontally levelled. There is small trick I read somewhere at the Apooge website. According to that trick, the side where the cable comes out of the unit, should be facing north, they say that doing it improves the readings.