In any design the sensor needs to be in air flow before radiated heat effects it.
Pulling air through hot plates does not work.
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but even that fan might be pushing. is it?? I donāt know. But imagine a normal household fan that is used to cool you down. You donāt feel a lot of circulation from behind the fan, but more in front of the fan.
In case of the shelter for the air, pulling might just be pulling from the bottom ring, where as pushing blows fresh air all the way to the top.
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True. My Davis Instruments Vantage Pro2 weather station is equipped with a 24-hour fan-aspirated radiation shield and the fan is indeed located at the top of the radiation shield (the installation is similar for the daytime fan-aspirated radiation shield, ie: the fan is located at the top of the radiation shield).
The purpose of having the fan at the top of the shield is to force the cooler outside air, not only from the sides, but also from the opened bottom (as is the case with the Davis Instruments solar radiation shields. The temperature and humidity sensors inside the Davis Instruments solar radiation shield are just below the fan.
Ray
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So, we went from discussing should the fan push or pull to discussing the fan is at the top.
Color me confused.
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And all this within āPhotos ofā¦ā maybe someone should split to āfan issues at air housingsā or similarā¦
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Looking at the fan Iām sure its pushing air that is not affected by the sun. Good design.
I would put fan at top pulling, with a solid tube to the bottom due to possible heat from
fan motor. Also I would hang it farther away from 4X4.
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My fan is sucking from below, and pushing air up and out. The fan isnāt on full blast, it is set to 6V, circa 900RPM. You can feel a little air flow coming out of each plate, even the top one. As I mentioned previously, as long as it is not blasting, it should work fine. I donāt really have any scientific evidence to say which way is better, but it is how I had my old DIY version for my Netatmo station, and it matched my Davis stations flawlessely. Hot air rises, so I donāt want to push it back down over the sensor. Davis isnāt fan aspirated btw.
Just as a testament, the Davis reached a low of 8.2Ā°C at 6:37am - The WF had a low of 8.1Ā°C at 6:40am.
Also, Davis is currently at 20.3Ā°C and the WF is at 20.3Ā°C - Iād call that a pass. Iām more than happy with those results. 
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my try, They only had 3 white pieces left, I can always add an extra one. as currently sun, very early or very late in the day might reach the air unit. However, it will be hanging in the shade 99% of the time. No fan. Itās now dark outside. Iāll hang it tomorrow. The screw with the black plastic is for fixing the air unit. I used a piece of aluminum strip and bend it at two places so it looks like a square bracket like this: ] It holds the air unit.
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Here is my setupā¦ Its beginning to look like ā¦ it means business
All I need now is the WeatherFlow Doppler 
Does the Air benefit from being up a bit higher, thinking about the lightning detection ?
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The US NWS has siting guides that recommend how high to put things. Basically 10m for the wind sensors and perhaps sternum-level height for temperature/humidity, with other recommendations for distances from surrounding obstructions. So the Sky is way low from ideal (but perhaps ok in your site) and the Air looks pretty good in terms of height.
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Almost finished my screen.
4 plastic ventilation grilles (see my post 5d ago above) that I have sprayed black inside to ensure its protected from any direct sun seeping through the relatively thin plastic. Just need to add the roof and then mount. Total cost so far less than Ā£20. Probably not a perfect Stevenson Screen by definition but I think itāll be good enough for my needs
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Howās the Metcheck screen working out for you? Just about to buy one, but thought Iād ask about your experience first!
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A test installation for the self made shield - I have a fan / solar panel ready to intergrate, just waiting to sort out the 3D print.
Itās still a bit wonky due to the printed nuts and rod but thatās an easy fix for a longer term installā¦
Edited to link back to the other thread with more details and the files to print - [https://community.tempest.earth/t/build-your-own-air-shield/144/101]
Andy
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So I made the decision.
Bought a Metcheck housing from the UK.
My AIR gives the temperature verry well. But itās to close to the bushes. Giving way to high humidity reading.
Will place a photo when it is installed in the housing.
If the AIR is placed in the housing I could just put it onto the fence?
Even if the sun is shining on it?
The airflow is way better over there.
To be continued.
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Great to see such good designs everyone.
My thought on the fan sucking or blowing is:
I was expecting someone to mention that the energy entering the motor is being converted to heat which warms the air before it is blown over the sensor.
And now that you mention ācolorāā¦
I believe that silver reflects more infrared light/heat than white. When the original stevensons screens were invented it made sense to use white paint because it was available. Nowadays silver paint is available and I believe would reflect more heat, so would work better?
Years ago I read a comparison of how much heat was reflected from metal roofs which included white and silver and showed silver as the cooler roof, but I cant find it now. Here is the type of comparison I read but it doesnt include silver now:
cheers Ian
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Screen is now complete. Iām pleased to see that even in direct sunlight the Air reported temperature is the same as my Davis VP2
My mounting options are limited so will probably sit on top of my shed.
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Nice work! Love it.
Iām to lazy ( read busy ) to build something like that 
Ordered one from UK.
Canāt wait to get that nice housing for the AIR.
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So far it appears to be working well, not witnessed the temperature spikes as seen on my old system, but have no idea how rain proof it is as rain has been in very short supply where I live. I am expect that horizontal rain from the south west will enter via the large opening at the back. Not sure if the AIR will be OK though.
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The fan uses meg lev technology, so the heat is negligible. The temps on my WF and Davis station are almost always identical. The only difference is the speed in which they update.
Couldnāt be more happier!
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So here it is. Received it within 3 days from the UK.
The Metcheck housing.
Installed the AIR at a different place with more breeze and where there is less solar radiation throughout the summer.
Love it! 
The Sky even reported 0.4mm of rain when I drilled the screws into the wood. Vibrations 
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