Thank you very much Anton! I'll try all of these ideas :) Also, I just talked to a friend who works for a company that calibrates medical instruments. They don't have a calibrated 'UV emitter', but they do have a calibrated UVA and UVB receivers (for babys that just born and need UV light). So my idea is to use any abstract source of UV (even sunlight), measure with a calibrated sensor and with mine.....and change my sensor coefficient calibration until I get the same result as the calibrated device. I hope this works!
About protection, you gave me a great idea..... I'll try to use one of these PIR sensors. [image: H9a8d776db26f4d1294d2be5175ecad93f[1].jpg] Em seg., 8 de fev. de 2021 às 13:45, Anton vanNwnhzn@GMail < [email protected]> escreveu: > Jonis, > > My first suggestions are for 2 very pragmatic solutions. > Calculation based on reported values for UVA and UVB incl. effects from > reported cloudcover is a solution in completely different league, for which > perhaps other group-members may help. > > 1) Perhaps *for testing of feasability* *start simple with "correction by > calculation"* > > *Be aware that openuv-values are always for 'clear-sky = without any > attenuation from cloudcover!* > > Based on your reported rough orders of magnitude > > - sensor-output reads UVI=19 > - openuv_value reads UVI=14 for 'clearsky', with OWM-value at same > level > - TV tells UVI=11 > > the order is TV < openuv_value < sensor_output > > With that knowledge you might apply a *very simple & very rude* * > scaling-function* like > > *Step 1*, to check if sensor_output already below openuv_value (because > if seeming 'practical', why rescale?) > if sensor_output < openuv_value then > real_UVI1 = sensor_output > > *Step2*, checking & reducing the value to get below openuv and fitting > 'reality' > if sensor_output *>* openuv_value then > real_UVI0 = sensor_output * 14 /19 > real_UVI1 = real_UVI0 * 11 / 14 > > Step1 just checks that sensor-output is plausible, > while Step2 is the equivalent of taking 50% of the sensor_output > Because you report that at night UVI from the sensor already is 0, no need > to check on negative UVI, nor check on range of values. > > *Result:* the calculation produces a UVI which *resembles* the value from > TV > ;-) Absolutely not scientifically accurate, but a practical solution > ....... > > 2) *Empirical attenuation by cap* > > For a similar problem with measuring light with a LDR/photodiode, I used a > deodorant-rollercap as attenuation cover over the sensor setup. > A very empirical solution, but very easy to try, and ;-) no cost: see the > pictures. > Negative aspect is that the colour of the cap *might* affect the reading > for UVI. > With cap fitted, compare the reported UVI with the value reported by TV. > If the reported UVI is lower than the value from TV, you might upscale the > reported UVI by ratio. > ;-) Also not very scientific, but a practical solution..... > > > Op 8-2-2021 om 16:06 schreef Jonis Maurin Ceará: > > 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] >> -- >> You received this message because you are subscribed to the Google Groups >> "weewx-user" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/weewx-user/4f966f35-f76a-4275-8212-f54161fbae41n%40googlegroups.com >> <https://groups.google.com/d/msgid/weewx-user/4f966f35-f76a-4275-8212-f54161fbae41n%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> >> -- >> >> =============================================================== >> Contactinfo voor Anton van Nieuwenhuijzen: >> Email = [email protected] >> Fax2Mail = (+31/0)84.8397303 [ook Voice2Mail] >> =============================================================== >> Deze E-mail en eventuele aanhangende files zijn >> alleen bestemd voor de geadresseerde(n). >> Als je deze E-mail ten onrechte hebt ontvangen, >> dan aub verwijderen en de afzender informeren. >> >> -- >> You received this message because you are subscribed to a topic in the >> Google Groups "weewx-user" group. >> To unsubscribe from this topic, visit >> https://groups.google.com/d/topic/weewx-user/zGNStvJwKKk/unsubscribe. >> To unsubscribe from this group and all its topics, send an email to >> [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/weewx-user/9d542c1f-7218-7376-e898-b2ac9544fbe0%40gmail.com >> <https://groups.google.com/d/msgid/weewx-user/9d542c1f-7218-7376-e898-b2ac9544fbe0%40gmail.com?utm_medium=email&utm_source=footer> >> . >> > -- > You received this message because you are subscribed to the Google Groups > "weewx-user" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/weewx-user/CACK8wihV6QWZu-0FPfesPfqrk%3DcX_hbV1tEn1h-6ssJi%2BZK3Aw%40mail.gmail.com > <https://groups.google.com/d/msgid/weewx-user/CACK8wihV6QWZu-0FPfesPfqrk%3DcX_hbV1tEn1h-6ssJi%2BZK3Aw%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > > -- > > =============================================================== > Contactinfo voor Anton van Nieuwenhuijzen: > Email = [email protected] > Fax2Mail = (+31/0)84.8397303 [ook Voice2Mail] > =============================================================== > Deze E-mail en eventuele aanhangende files zijn > alleen bestemd voor de geadresseerde(n). > Als je deze E-mail ten onrechte hebt ontvangen, > dan aub verwijderen en de afzender informeren. > > -- > You received this message because you are subscribed to a topic in the > Google Groups "weewx-user" group. > To unsubscribe from this topic, visit > https://groups.google.com/d/topic/weewx-user/zGNStvJwKKk/unsubscribe. > To unsubscribe from this group and all its topics, send an email to > [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/weewx-user/fab4f4d1-8aeb-8c28-8dbc-58706f3545df%40gmail.com > <https://groups.google.com/d/msgid/weewx-user/fab4f4d1-8aeb-8c28-8dbc-58706f3545df%40gmail.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "weewx-user" group. 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