Solar Radiation Shield

[Karl in NY]

I'm new to this (as a hobby), and to the forum.

That said, I have a Fine Offset system on order (actually, on extended back-order, an Ambient WS-1090). I do have a background (in a former life) of being a meteorological and air-quality technician, so I'm not at ground-zero, either.

Despite it being sunless here now in Northern NY, I'm giving thought to solar radiation shielding of the temperature sensor.

I have several options, including running 35' of cable to place the sensor into the Northern shadow of my shed...it will still get limited direct sun exposure, however.

I have also considered fan aspiration, using a DIY solar-powered fan, and not relocating the temp. sensor.

I'm also considering making a cylindrical "tent" around the sensor, using mylar-coated bubble-wrap, fabricated from a cheap (~$5.00) car windshield sun barrier. My feeling is that if I can maintain good air circulation, yet provide shade and a reflective surface facing the sun, I should be OK.

I haven't worked out the mechanics, but a primitive/temporary approach will be to simply wrap the shiny stuff around a wire tomato-cage, with the sensor inside, with open bottom and top to promote good convection across the sensor element.

Has this approach been tried, and either been found to be adequate, or, to be useless?

I want to contribute accurate data...but, I realize I probably won't to be able to do multipoint calibrations of the various Fine Offset sensors like I had to do professionally...but, right now, I'm on a budget.

Thanks for listening.

-Karl

[Karl in NY]

As a new member, with a new posting, I'm kind of underwhelmed by the lack of replies...

Perhaps my posting lacks merit? Perhaps it's too naive to even respond to?

If so, please respond and say what a useless post it was, and how it has been answered a hundred times before...and why didn't I do a search before posting...

Or, is this forum pretty-much "lacking", in general?

[captzero]

Hi Karl,

Welcome to the forum,

I think with time you'll find that the forum and its members are very helpful and quite knowledgeable and usually respond fairly quickly.

Having said all that...

You ask whether anyone has used some windshield sun barrier to shield the temp sensor. I've not heard of anyone using that method on the forum (maybe the reason for the lack of a speedy reply) but it couldn't hurt to try it. There are lots of discussions on the forum about how members have made home made FARS and Stevenson Screens.

Try

https://cumulus.hosiene.co.uk/viewtopic.p ... hilit=FARS

https://cumulus.hosiene.co.uk/viewtopic.p ... =stevenson

Cheers

[MickinMoulden]

I find this forum fantastic, I have had helpful replies in a respectful and informative manner. I've only just come on-line to read this. And Karl, your idea sounds fantastic, wish I had thought of that myself, and in addition to your idea in the same theme, could I then also suggest you make a raised "hat" for the temp sensor so that no direct sun will hit it when the sun can reach directly over the top.

How much will a motor contribute to added heat I wonder? Perhaps the air that is pushed over the sensor is not drawn from over the motor. Separate the motor from the fan blades with the mylar coated insulation and your on your away. (make sure your design won't hold water though

[wd40]

I bought the solar shield from Ambient. If you check with wunderground, there is a code for a discount of the station. Buying the optional solar shield with the unit using the code with help with the budget. On the Wx forum, there are a few folks that make them out of plastic bowls.

Randy

[tjaliwalpa]

I am planning to use a set of platic plates that will allow for free airflow as well as shade the sensors from the sun. I have yet to find the shaped plastic plates. I will model my design on that of a fellow member, "hills". Here's the link to his modification:
http://members.ozemail.com.au/~storerf ... tled-2.jpg

[MickinMoulden]

I am planning to use a set of platic plates that will allow for free airflow as well as shade the sensors from the sun. I have yet to find the shaped plastic plates. I will model my design on that of a fellow member, "hills". Here's the link to his modification:
http://members.ozemail.com.au/~storerf ... tled-2.jpg

Probably best to use stuff that won't heat up and radiate heat though. Although I must admit not doing anything to mine (although I have tested it without the shield and it changed up to 3c). Mine is under the eve of the house.....and will change the location where it will be shielded from UV and from any radiated heat source (covered with bubble roofing insulation).

[Orion]

As a new member, with a new posting, I'm kind of underwhelmed by the lack of replies...

Perhaps my posting lacks merit? Perhaps it's too naive to even respond to?

If so, please respond and say what a useless post it was, and how it has been answered a hundred times before...and why didn't I do a search before posting...

Or, is this forum pretty-much "lacking", in general?

Or perhaps most of us in the UK are asleep

[Gina]

Or perhaps most of us in the UK are asleep

Yes. Either that or going to the toilet I personally will only on-line if I can't sleep.

[robynfali]

I think at the time of posting this, most of the UK was asleep lol, hence the slowness in replies, dont take it personally mate, you will get loads of advice and help on here, i know I did!

[Gina]

There are lots of posts on here about radiation screens. They are generally called Stevenson Screens. There are many different designs both the Met Office square boxes and various round ones. I think most posts are in this forum but there are probably some in the Fine Offset sub-forum. Plenty of reading to do

To answer the original question though - I wouldn't recommend bubble wrap. The basics are to shield the sunlight and reflect the heat away and to provide good ventilation.

[artworksmetal]

.....To answer the original question though - I wouldn't recommend bubble wrap. The basics are to shield the sunlight and reflect the heat away and to provide good ventilation.

I think the term 'bubble wrap' may be misleading. Most of us think of the stuff to pack your grandma's fragile vase with. Those mylar coated windshield screens are very reflective, and a bit more substantial, really. I've never seen one that reminds me of bubble wrap. Most of the ones I've seen look more like cardboard.
Sounds like a great starting point. Got me to thinking - I've got some foil coated insulation from my Big Box Hardware store, used to wrap ductwork. Very flexible and water resistant, but sturdy.
I think with good ventilation, the fan shouldn't be required.

[Ned]

That sounds like the stuff I used - 3mm foam sheet with a highly reflective (Mylar?) coating. It was supplied as a vapor barrier underlay for flooring I laid, along with thin mylar reflective tape for joining it.
I wrapped a sleeve of the foam around the FO weathershield, taped up the joint and top edges and applied more tape to the top cap. Cut 12 slots in the foam corresponding to openings in the shield and taped the edges. I could have cut more slots for ventilation but my aim was to minimise solar gain - think I achieved a good balance. The top and bottom openings are unobstructed for convection currents.
That was done last July and rough measurements at the time (in winter sunshine) indicated the solar temp gain was approximately halved over the original shield, from about 3° to 1.5° degrees (compared to full shade).
Since then I have relocated the transmitter onto a wall under the eave and it never gets direct solar radiation, but left the reflective shield in place. It's still in great condition.
I wondered if the reflective coating might block radio transmission but it's worked normally, at least over a short distance I use.

[Karl in NY]

Thanks, all, for the comments.

Ned's photo comes pretty much to representing my thinking on the subject...

I was going to use similar metallic (aluminized, or, for ya'll Brits, "aluminised") foam or air-bubble material, but actually spaced-out from the original OEM radiation shield...I think my concept would be technically better than Ned's implementation, but would be more difficult mechanically.

I think I will eventually duplicate Ned, plus move the sensor into a location that gets 80% shade.
I may still use the stuff wrapped around a tomato-cage, though...

(do Brits know what a tomato-cage is, or is that a US-specific term?...FYI, a rigid wire cage used to support tomato plants in the veggie garden...)

[Ned]

Karl, keep in mind increased wind loading on a large diameter shield - think storms! The FO mounting is adequate for mine but maybe not for anything much larger, where I think you'd need a well engineered mounting system independent of the transmitter (as it is).