Topic: Calibrating UVI values?

[Jeje2]

How can I calibrate my UVI values to match my area behaviour...

I live in an area where theoretically the MAX UVI is 6 and that can only be reached for +- 1 week of midsummer (24.6) for 4h (11 - 15) per day...

So starting tomorrow the UVI value of MAX 6 is theoretically possible, so far this year the MAX UVI measured in my region has been 5 (according to local meteorological institute).

But now my Ecowitt WS68 has already given MAX UVI of 9 this June (also in 2022 it was max UVI of 9)
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So the orange line should be the max until today...  and for the liget yeallow box time it should be MAX 6, indicated by the red line...

So, how could I calibrate this? Is it possible?

By looking into the maintenance software of the Ecowitt GW 1100 I have - I can see in the calibration view a couple of values that might do it...
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But is it linear multiple to think about or how should I calculate the calibration values? And which ones?

Sure would be nice to get more accurate UVI values...
(Same with wind, but as my WS 68 meter in nonoptimal position, hinders too close, it can't even give accurate values...)

[hiljo]

I'm using a UV-gain factor of 0.60 (here in the Netherlands). Somewhere on the forum here I read that that should approach the real UVI factor.

UVI values are just like sunlight and rain very local. So if the meteorological institute is at another location of your sensor, the values can be different (because of pollution, clouds, etc) in the sky.

[Gyvate]

for me (Central Europe, 49° N) 0.55 turns out to be a good match.
Best is to wait for a day with long time blue sky and compare the factor 1.0 readings to the next meteorological station.
That will give you a good approximation.

[Patt21]

What is the best sun sensor between wh68 and wh80?
I wonder about the wh68 in June, long days, if it measures rays well in the early morning and late evening, compared to the WH80.

[Gyvate]

WH68 and WH80 I don't know. They don't exist.
But there are WS68 and WS80. see https://www.wxforum.net/index.php?topic=40730.0 and understand why it is "S" and not "H". 
The sensors built into WS68, WS69, WS80 and WS90 are the same.
If you want to compare, you have to make sure they are at the same height and equally exposed to solar irradiation.
In principle, under the same conditions, they should provide the same readings.
You may also need to consider that they have different reporting/transmission intervals (4.75, 8.8, 16 seconds - see also https://www.wxforum.net/index.php?topic=40730.0)