Cumulus Support

As AllyCat said in 2011

"performance of all those Fine Offset screens in direct sunlight is very poor (I've measured around 5 degrees C rise above ambient air temperature) so it needs to be located in a "shaded" position, or a better "Stevenson Screen" design would be preferable."

I can neither afford the money or space for a Stevenson Screen but wonder what folks think of the typical plastic cover for the temperature transmitter. Is it worth spraying it black/white/silver or covering it in silver foil. Mine is already in a shaded place but it still occasionally catches the sunlight. Also it is going a darker shade of grey , can't remember if this was original colour as it is 6 or seven years old.

I think this applies to other units as well hence why I posted here.

Before doing any spraying of the actual cover, do consider cheap extra screening like that discussed in viewtopic.php?t=17954

I had looked at that before posting but thanks anyway.

I have a spare cover from an old battery hungry transmitter which I will try when (and if) I get a consensus of opinions....

Okay, to respond to your original question, the darker grey (and I am sure yours too would have been significantly lighter colour when new) will absorb more heat.
In that respect, spraying with white, or adding a foil covering, would reflect some heat.
However, the poor performance in sunlight is not quite that straightforward.

watsonm wrote: ↑Sun 03 Apr 2022 12:41 pm I had looked at that before posting

I knew those earlier posts were easy to find, but decided to post purely because of your initial comment about not having enough space for stevenson screen.

At a previous location over effectively a decade, I tried a variety of methods to try to improve Fine Offset temperature performance in sunlight, whilst keeping the sensor at the standard measuring height. For example locating in a home built wooden stevenson screen, outside that but with plastic picnic plates round the Fine Offset screen to make a more effective set of shading, and locating in various shaded places with different amounts of exposure. None of my experiments yielded any improvements, although I saw a few obvious discontinuities when long term plots viewed.

At my current home, (effectively surrounded by hills), I started with a fairly shaded place, and still saw correlation with sunshine.
Then, with advice from professional Freddie, I tried the new very high exposed location with "cage" as described in other topic.
I remain amazed at how successful it has proved, there is now very little correlation with sunshine, and each daily temperature range seems reasonable. Freddie said the important issue was to move it away from surfaces that could absorb and release heat. He is obviously right about improving exposure, although the extra set of vents has contributed by shading the air outside the fine offset cover. The mast was blown down in Storm Dudley, so now there are two clamps, professionally installed, holding the mast onto the gable, but otherwise the same arrangement has served me for over 2 years. I better not tempt providence by mentioning the various ages of my sensors, all were in operation at two previous homes!

Many thanks for your comprehensive reply. After some googling this afternoon I had decided to spray my spare unit white which
I will do sometime soon.

Interesting idea from professional Freddie...
My temperature unit is sited 1 meter away from a north facing wall which only gets a bit of sunshine in the peak of summer. It is screwed to a wooden north/south fence which is a relatively poor heat source and occasionally gets a short early morning burst of sun which is causing my problem. Any further than 1 meter away will result in more sun!

I may try putting my spare unit elswhere to see if that yields any better results. (I am directly read the radio transmissions from two transmitters already so another one won't be a problem

Thanks again Mike