Getting UV Index

[marianowadel]

Hi, thank you for your work. This library works ok in my setup, while others didn't. Do you know how can we convert the output to UV index? I need to report my readings to Wunderground, and they don't take w/m2 for UV readings.
Thanks again!

[cmur2]

I also researched that when I wrote this library and sadly the conclusion is that it's difficult. You can get a glimpse from Wikipedia:

The UV power spectrum (expressed as watts per square metre per nanometre of wavelength) is therefore multiplied by a weighting curve known as the erythemal action spectrum, and the result integrated over the whole spectrum.

Since the VEML6070 from Vishay (peak sensitivity according to datasheet at 355 nm +/- 20 nm) does not measure the wavelengths that are most important for the UV index (around 300 nm as far as I understood) you could only get rough estimates. The best you can do is doing relative comparisons for your own... submitting the estimate to Wunderground might have some downsides e.g. for other people who trust the value and get hurt.

Maybe there is also another sensor out there that matches the required wavelength spectrum more appropriately. Anyways happy that it works for you :)

[marianowadel]

That's so disappointing :(. I've read a little more and from here I understand that the really harmful UV light is UVB (VEML6070 measures only UVA). Anyway, before this I was using a SI1145 (visible light meter) to estimate UV index. VEML6070 seems much more realistic and close to nearby stations. I guess the way to go would be VEML6075 (also measures UVB), but the wavelengths don't seem that different from VEML6070's (355nm +/- 20nm vs 365nm, 330nm +/- 10nm).
I divided by 10 your library readings and my values are somewhat close to a nearby Davis Vantage Pro. I also had to take into account the attenuation of the enclosure, which is made of glass.
Anyway thanks for answering!
Cheers and again thanks for your work.