Homebrew Weather Station Aspirated Solar Shield
In an attempt to improve the accuracy of my Temperature and Humidity readings, I decided to make a new Solar Shield, that might be less affected by direct sunlight. While searching around on the Internet, I found an article describing a "Coaxial" Solar Shield that used a small muffin fan to pull air past the Weather Station Temperature & Humidity Sensors. Using their idea, I came up with my design.
I purchased a 2 foot length of 6" PVC pipe from Home Depot, and placed an online order for two 90° 6" Elbows to construct the outer shell of the new Solar Shield. I also purchased a length of thin-wall PVC pipe to use for the inner (Coaxial) pipe that would house the Sensors.
Here's the Home Depot Link for the 2 foot 6" PVC Pipe
The 6" pipe was drilled and tapped for 1/4-20 Stainless bolts, in 6 places, to hold the inner pipe in place. This allows the inner 4" pipe to be removed for maintenance, if necessary. The 4" PVC pipe is slightly shorter than the exterior 6" PVC pipe, allowing the muffin fan to pull air thru both the 4" and 6" PVC pipes at the same time. The two 90° 6" elbows were glued together using a 4" piece of the 6" PVC pipe that was initially removed. The bottom of the 6" pipe is approximately 5' above ground, where the air is drawn in, and the 90° elbows are positioned to be down-wind from the prevailing wind direction. The elbows can be removed for muffin fan maintenance.
I cut notches in the top of the 6" pipe to retain a 4" muffin fan, which is powered by a wall-wart from my garage. To seal around the muffin fan, I made four small wedges that were held in place with Silicone RTV. The edges of the fan were smoothed with a file to match the exterior of the 6" PVC pipe, enabling the 90° elbows to be slipped over (Not glued) the top of the exterior PVC pipe. This keeps any rain from reaching the muffin fan and sensors.
Mounting the completed unit was accomplished using some "strong-Tie" brackets also obtained at Home Depot.
I thought of placing a piece of piece of nylon window screen on the bottom of the 6" PVC to keep bugs out, but have not yet got around to it.
Below are some pictures of the new Aspirated Solar Shield. I suspect it has improved the accuracy of my readings, however I have no way to verify it. I have noticed the the temperature readings appear more stable than with my previous solar shield.
Hope you find this interesting
COMPLETED SOLAR SHIELD
VIEW FROM TOP SHOWING MUFFIN FAN
VIEW FROM BOTTOM SHOWING INNER PVC PIPE AND SENSOR MOUNTING