Why are my solar radiation readings higher than the solar constant? (SPN1, BF5, GS2-05)
Sometimes, during the day, the sensor may read higher than the solar constant (greater than ~1370W.m-2)
This is something that has been seen in rare, isolated conditions. This can usually be caused by:
- Certain types of cloud cover magnifying the sun’s rays and increasing the irradiance. This tends to be when cloud cover is sporadic and the sunshine is intermittently broken up as the clouds pass by.
- Water on the dome/sensing diffuser, again magnifying the irradiance seen by the sensor.
- A nearby reflective object shining onto the sensor (this should be noticed at a similar time of day, every day during the same season).
These events are extreme and of short duration. They also tend to get lost if you only keep averages of the series (e.g. 1 minute samples logged every hour).