[werk_ag]

Hi,

....also useless, including Davis, I think.

No I don't think so. Davis may use a similar sensor, but they do add the correct "Erythema Action Spectrum" filter, which perhaps explains why their sensor is so expensive (hundreds of Dollars/Euros/Pounds). See the Data Sheet here, noting the spectral response at 360 nm, and the logarithmic vertical scale.

I should have answered early, but ...
Thank you for this clarification.

However, to be more positive, my own experimental "Solar Sensor" ...

It seems you do things in a very scientific way. Maybe sometime you share with us your experiments... I would like, and certainly would learn a lot.