Another UV calibration in the morning and still off

It looks I got another calibration for UV this morning. In the end the max UV matches the national one almost exactly. (sky max 7.1, national max 7.6) . However the values in the late afternoon are almost double of what is expected (sky 3.5, national 1.8).
I already had a feeling that the values were too low. That seems to be corrected for measurements around 7 but for the lower values (like 3.5) it is way off.

I’m wondering of the scaling is only a simple multiplication, which will never produce a good result, judging from these measurements.

edit: currently sky 2.2 vs 0.8 national. still clear skies.

(note, clear skies, no influence from clouds)

Mine doesn’t even calibrate… My maximum UV is constantly about 6.
En around this time it could even peak to UV 8…

Yesterday it should read higher than 7. But my maximum was 6.3.

you can see that it does a calibration when there is a jump in uv, but not a more or less corresponding jump in solar power/brightness. Yours didn’t show that jump. Today there were clouds again, so no the right circumstances to do a calibration and yours reached 9. That high value is about the 20-25% extra one can expect on semi cloudy days. Rivm tells us the expected max for today is more around 7.4 (clear skies)