Ok, thank you guys!
Here, in Ribeirão Preto, I'm getting almost everyday warnings on TV about
extreme UV levels, so I'm pretty sure it's more than 11 almost all day. But
in my opinion, 20 it's too high.
I have tried both openuv.io and ogimet....
openuv.io shows me:
"uv": 0.041,
"uv_time": "2021-02-08T14:54:53.953Z",
"uv_max": 13.664,
while my sensor is reading 19. Ok, it's a little cloudy now and maybe this
measure from openui is during a shade.....still, max UV is a way low than
my real reading.
ogimet I could not find any station here in Ribeirao Preto with UV value.
but looking at openweather map, I could find a value of 14 for UV. It's
almost the same of openuv.
Now is the complicated part.....
1) What do you recommend to use as protection for the sensor? I read about
teflon diffuser (with 0.4mm thickness), but It's hard to find this. I was
thinking about printing a case and use a mobile phone glass
creen protection (very thick) as protection. What do you think?
2) I'm getting values from UVA and UVB from sensor in mW/cm². if I'm right,
weewx expect data in W/m², right? If I convert my current UVA value
(8,809mW/cm²), I'll get 8,8W/cm².....and converting to meters, it's
0,00088W/m². Is this right? I'm thinking its too low.
3) Finally, I have sensor coefficients to play and calibrate values. These
coefficients are 4 values, a,b,c, and d. B and D are for UV light itself,
if I remember the tech docs that I read. My question is: since UVI uses UVA
and UVB to be calculated, I'll have to play with both. Do you guys have any
idea or type how to start calibrating this without any expensive equipment?
Of course I don't expect perfect values, since this is just a hobby. But I
would like to get as close as possible to real value, using accessible
things to calibrate this sensor.
I know that this is a hard and complicated task to do, especially without
adequate equipment. But I would like to have some ideas from you, more
experienced users.
Em seg., 8 de fev. de 2021 às 04:58, Anton vanNwnhzn@GMail <
[email protected]> escreveu:
> For clear-sky reference values you could look at https://www.openuv.io/
> That site provides info dedicated for the location you ask:
> info includes much more than UVI only.
> For automatic extraction of info a script will be needed.
>
> If you want automatic info on attenuation by clouds, then
> https://www.ogimet.com/home.phtml.en is your friend:
> look for it's octa-values for your location [=WMOID] through the url
> "http://www.ogimet.com/cgi-bin/getsynop?block='..WMOID..'&begin='..UTC..'"
> <http://www.ogimet.com/cgi-bin/getsynop?block='..WMOID..'&begin='..UTC..'>
> Or look for a weathersite in your area providing values for cloud-cover.
> With that info [= 'clear-sky'+ 'octa'] you are able yourself to calculate
> the expected practical UVI.
> Op 8-2-2021 om 1:10 schreef [email protected]:
>
> Hi!
>
> I would like to know if these values are plausible for UV sensor here, in
> Brazil.
> I'm located in Ribeirao Preto, SP, Brazil (-21.1767, -47.8208) and the sun
> is very 'hard' here. We are almost in tropical line and the sun pass almost
> 90º degree above us at 12h00 pm......also, we are just in the summer. So my
> question is: UV Index of 18~19 is a plausible value? peak of 20.
>
> I'm asking because i'm testing a new sensor in my station, VEML6075....but
> I'm first trying it standalone using arduino and this library (
> https://github.com/adafruit/Adafruit_VEML6075 ). Acording to this
> library,m the default values (calibration coefficient) are for the sensor
> direct in the sunlight, without any protection. That's how I tested today,
> sensor direct in the sunlight....but I'm thinking that 18~19 are too high,
> even with our 'brazilian sun'. It's very hot here, about 38~40 in the shade.
>
> If I use the sensor indoor at night (just using my LED home lights), I got
> negative values in sensor (UVA and UVB, not index), but I think that's
> right, since LEd doesn't emmite any UV light and sensor has calibration
> values, right?
>
>
>
> Here are the values that I got (just some samples). The lower value is
> during the shade of a cloud, but still very bright.
>
>
>
> [image: 3.jpg]
> [image: 1.jpg]
> [image: 2.jpg]
> [image: 4.jpg]
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