SI1145 and UV Index

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lizny
 
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Joined: Fri Oct 18, 2013 11:19 am

SI1145 and UV Index

Post by lizny »

I don't really have a problem, but thought I'd start a thread to accumulate some general information for myself and any other interested parties.

I took my breadboarded sensor outside this afternoon and aimed it at the sun, which was then around 40 degrees elevation. I propped up the breadboard so the light would hit more or less directly on the sensor. Clouds where going in and out, but I got some clear sky and full sun measurements were in the nines and tens. I was a bit doubtful because readings in that range are described as 'very high' risk of sunburn, and was around four in the afternoon almost two months before the solstice in NYC.

This map: http://sunburnmap.com/ gives a maximum of 5 for New York today but I think that takes into account the partial cloud cover, whereas the previous one assumes clear sky. http://www2.epa.gov/sunwise/uv-index has similar results and definitely says it includes weather forecast data.

Looking around, I found this site: http://www.temis.nl/uvradiation/nrt/uvi ... &lat=40.67 which predicts the UV index for a given lattitude and longitude at noon with clear sky. It gave me 8.5 a bit lower than what the SI1145 read, but not crazy different.

Interestingly, that calculator gives calculations based on the predicted ozone column, so the readings don't steadily climb going forward towards summer. I wonder if I can reverse that: using a SI1145 measure the UV index at solar noon for a given location and back-calculate the actual ozone protection from that data.

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