UV seems too high or too low (solved with auto-calibration CL system)


SKYs were installed a few months ago. They should have been calibrated until now.

Maybe one of the units has a dirty sensor screen. Have you checked both?

I have not checked if one sensor is dirty, but I don’t believe it is, because there were long and heavy rains the last days that cleaned everything around. But I’ll check it tomorrow.

Yours is another where the CL system hasn’t had enough days to apply a calibration, yet. We’ve applied a manual adjustment that should produce much better data, and this will get better after the CL system collects and processes more data.

Interesting… you may have uncovered a bug in stations (thanks!) with two SKY units as both units have enough data for confident calibration. but the update was only applied to one of your units. We’ll look into that and meanwhile, we’ve applied the calibration to both of your units. They should agree much better with each other (and reality) as soon as the sun comes up!


Much better. Thanks so much.

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I install Sky unit 9. december and then reset data 13. december when I set Sky on my roof.
In a period from 9. to 13.12 I have one sunny day, after that in december I don’t have any more sunny days.
In January I have nearly 9 sunny days. No full sunshine but mainly sunny in more of this days.
My Sky and further give bigger values then real.

@anon84912554 I think my station (4848) has low UV readings. Could someone please check if my station has had a calibration applied.

@anon84912554 Mine is still reading about 2 points lower than the official reading. Not sure this auto calibration is working? We have had plenty of clear days lately so that shouldn’t be an issue.


Hi Gary. Thanks for your feedback (and patience!).The CL process for UV is still a work-in-progress. It has been pretty conservative about changing a calibration to date but we are about to implement a change that should improve the ongoing calibration and also be more aggressive about deciding when to apply it.

That said, it’s possible you have a faulty sensor or something else is going on. Looking at your January data it definitely seems be to reading lower than it should. We’ll dig in a little deeper and you should see your data get better soon.

Thanks for the input. Your SKY’s UV sensor was auto-calibrated on 23 January. Has your data looked better since then?

No auto-calibration, yet, but your values definitely look low. We’ll apply a manual calibration today based on a human analysis.

Oh yes much better. :slight_smile:

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Hi I have checked my stations 4664 UV against the official ones at
Canberra and found that they are showing about half of what I would expect them to be.
Canberra lies about 150km to the south and has similar weather conditions to our area. eg yesterday Canberra max UV 11.1 @ 13:23 mine 6.8 @14:00, a very long way out
Information for Australian conditions can be found here https://www.arpansa.gov.au/our-services/monitoring/ultraviolet-radiation-monitoring/ultraviolet-radiation-index
The graphs are updated every minute

Thanks. The readings now look more like I expect.

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Thanks for the report, John. Your station is one of hundreds that just received an adjusted calibration under the latest iteration of the CL process for UV mentioned above. You should see better UV data starting today!

Thanks also for the link to the Australian UV info. Good stuff!

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Thanks David I’ll keep an eye on it and let you know
Thought you might like a link to the Au UV site as it might help to calibrate the Skys in Oz

Hi @dsj

It seems like my calibration was updated and is now reading very high.



cheers Ian :slight_smile:

Hi Ian. Thanks for the report. Your calibration was indeed recently updated, but not enough to explain that big increase! We’re going to take a look at your debug data - something else may be going on here. Stay tuned.

Hi @dsj I agree with @iladyman it looks to me that the readings may be up to 3 points too high.
I would not have expected a reading of 17+ in these latitudes according to the predicted ones of 14 max, (a bit hard to tell out here as we are not real close to a working station) although it was a very bright day.

Yes, I think ~17 is too high even for the AUS/NZ summer!

We’ve confirmed this is not related to the auto-calibration process. Rather, it looks like a case of spurious “spikes” in the readings. We’re going to pull out the solar simulator and run some tests to try and figure out what’s going on. Thanks for the reports!

Thanks David, looking forward to the results.

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