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skyewright wrote:I'm not sure where you get the impression that the expensive solar sensors are not accurate.

Ok, I think I thought more than I wrote, sorry:

Not accurate: The OS UV sensor
Expensive (but accurate): Davis solar sensor

skyewright wrote:Accurate: No.

Here my impression was that the results (in terms of the plots) are quite similar to the ones from "real" solar sensors. This I referred as "accurate" which is not correct, yes. Therefore I fully agree that it's more useful as an indicator. But this is a lot in my opinion, given that the WMR928 does not support any sensor to measure sunshine hours or solar power.

nduku wrote:

skyewright wrote:Accurate: No.

Here my impression was that the results (in terms of the plots) are quite similar to the ones from "real" solar sensors. This I referred as "accurate" which is not correct, yes. Therefore I fully agree that it's more useful as an indicator. But this is a lot in my opinion, given that the WMR928 does not support any sensor to measure sunshine hours or solar power.

Oh yes, it's very useful and in the years before I got the Davis solar sensor I greatly appreciated the data it provided - you just need to take the W/m2 figure that some software translates it into with a large pinch of salt (as we say in the UK).

Even though I now have the Davis sensor, I still run a "temp in a jar", though now I mainly only use it as a night time cloud detector and so I have optimised the design towards that purpose[1]. You'll find more about this use on the Weather-Watch forum. A handy thing about the night time cloud detector is that the temp difference for 100% clear doesn't vary through the year, so you don't have to keep adjusting the settings.

[1] My "jar" is actually a polystyrene filled pipe, with a blackened foil disk slightly recessed in the top, and with the top covered by a piece of glass. The tip of an OS THC138 is in the middle of the foil disk. With this design I get a night time "clear sky" difference of -3.7C.

At this time of year, the day time clear sky max difference with this set up is 58C! With my previous design, which really was a jar, the max daytime difference in summer was 35C, and the max night difference was -2.6C