Temp sensor & sunlight

In the damp dark days of spring, I thought I’d sited my outdoor temp sensor somewhere that the sun wouldn’t reach. Solar precession and sunny mornings have proved me wrong :oops:

As I don’t have a Stevenson Screen, does anyone have any tips for shielding the sensor from the sun using commonly available materials. Is it good enough just to put something around the sensor so that it’s always in shadow?

I like this site:
http://wxqa.com/shields.html
Also, you may like to read this thread:
http://weather-watch.com/phpBB2/viewtopic.php?t=1309

I have finally placed my outdoor temp sensor in a Davis Radiation Shield (still got hot in the sun) on the North side, in the shade from the house. I found it almost impossible to place the outdoor temp sensor where it was not affected by direct or indirect solar radiation.

Chris,

grhughes posted details of his (great looking) homemade one in the “weather pagoda options” thread. Unfortunately the links to pictures aren’t live anymore but I’m sure he would put them up again.

Thanks.

I’ve learned a valuable lesson here…look in your own backyard (the WW Forum) before asking questions that have already been answered :oops:

Hi Chris
I finally solved this one by mounting my temp sensor on a wooden fence 5ft aboveground level.
The fence faces SE but is screened from direct sunlight by my 12 ft high
building [Southern Hemisphere]
The sensor is mounted in a vented polypropolene burgler alarm siren housing which protects it from rain.
The only time of the day direct sun hits fence on NW side is for about 1hr
in the late afternoon & I prevented this from affecting readings by putting a heat deflection shield on the back of the fence [old piece of white formica]
This system works great year round without direct sun affecting readings at all. Also as fence is 3 ft away from building get good night readings as well. [Night air is usually calm with frosts in winter]
The Met Service uses my temp & rain figures from both my stations as being accurate enough to publish in the DomimionPost newspaper as local
area readings

http://www.weather-watch.com/phpBB2/viewtopic.php?p=6533#6533

8. To deal with the problems i had, i built mine inside a bird house. 12 Inches tall, 4 inches wide, 4 inches deep, all i did was take the front panel off the bird house,(where the birds enter) then placed my sensor unit in there. Then took the front panel and cut it in half, and put the half door back on with hinges from the top so i could flip up the door., and covered the bottom half, with standard window screen meterials. Problems arose pretty quick, color of the bird house was the first issue, it was a dark brown color (weathered), it absorbed even the littlest sunlite. I painted it white. Seemed to be ok, but i neglected to take into account he rotation of this planet and the tilt of its axis in different seasons. Soon the sun was beating directly on it. White or no white it was absorbing heat like a sponge. In a last ditch effort i put reflective meterial, (Chrome covered sticky paper) on the top. Worked ok , but didnt like the weather and fell off. Since i build computers for a living, i thought, well if I can can keep a computer cool, i can keep this cool. I took a DC 12V Case fan, 4500RPM, and mounted it inside the box. I cut a whole in the side of the box the same size as the blade diameter, as so i had extra space for the mounting screws. Then i covered the hole with standard window screen, 90mm is enough. I ran a wire from my house, 20+ feet way, to an old power pack i had from a cell phone. Degredation is another key problem in electric, not enough juice to run the distance, via the wire size i had. I was running out of patience. So i mangled an 4 pin lead for a computer and plugged it directly into my computers power supply. Now based on temp gauges i have all over the place, it reads pretty much right on. Cept when it drops below freezing here, humidity refuses to read. If you want to build one contact me. I got the specs.

I have had the same problem recently, showing over inflated readings whilst the sun shines directly onto the sensor.

I have resited the sensor behind the shed away from the south facing side, and the fence obscures the west side. The east side was exposed until yesterday, when I found the sun was hitting the sensor yet again. As the the sensor is screwed to the side of the wooden shed, I have placed a strip of bright aluminium of 12" x 6" to cast a shadow over the sensor. This has angle of 2" width to enable me to screw this to the shed and adjacent to the sensor. It is a case of bodging, but it works.

Hi All,

I built one of these
http://weather.overflow.net.au/station/stevenson.html
and it works very well and looks pretty good as well.

Here’s some additional Weather Station Housekeeping Info:
http://wxqa.com/resources.html

From the NWS COOP Web Page:
http://www.nws.noaa.gov/om/coop/standard.htm

Temperature sensor siting: The sensor should be mounted 5 feet +/- 1 foot above the ground. The ground over which the shelter [radiation] is located should be typical of the surrounding area. A level, open clearing is desirable so the thermometers are freely ventilated by air flow. Do not install the sensor on a steep slope or in a sheltered hollow unless it is typical of the area or unless data from that type of site are desired. When possible, the shelter should be no closer than four times the height of any obstruction (tree, fence, building, etc.). The sensor should be at least 100 feet from any paved or concrete surface.

Precipitation gauge siting: The exposure of a rain gauge is very important for obtaining accurate measurements. Gauges should not be located close to isolated obstructions such as trees and buildings, which may deflect precipitation due to erratic turbulence. To avoid wind and resulting turbulence problems, do not locate gauges in wide-open spaces or on elevated sites, such as the tops of buildings. The best site for a gauge is one in which it is protected in all directions, such as in an opening in a grove of trees. The height of the protection should not exceed twice its distance from the gauge. As a general rule, the windier the gauge location is, the greater the precipitation error will be.

Cheers,

DaveH

Before i got my Vantage Pro station, I built a Stevenson Screen my self, and placed it in a shaded spot. Putting the sensor in a shaded spot without protection will do no good, since UV light reaches shaded spots and can effect your sensor. Plus, at night the unshaded sensor sends out infra-red waves that make it colder than it’s surrounding. so i built the screen and put it under a small piece of ceiling next to my window. Here is the result: http://www.tapuz.co.il/forumsArticles/images/442_95.jpg

It works great, and best of all, it’s not that hard to build! I wrote an article about it but not in english, but if you need any help i’ll be happy to give it to you.

Now summer is here (got my station last September) the sun is hitting my sensor, also when the sun is not directly on the sensor it is heating up adjacent walls etc to give a false hi reading

Daft question, is there any reason when the sensor cannot be placed inside a large garden bush?

I have just done some measurements and although the bush is in full sunlight the middle of the bush is measuring the correct air temperature which is about 3 deg less than my current station sensor.

This seems to be to simple an answer!

Thoughts please.

brian, there could be a problem with that. Temperature wise, when it gets drier and you have some clear nights, the bush is going to hold in the heat and make your temps higher than they actually are. If the humidity sensor is with temp. then you will have a problem because the bus will transpire mositure which will raise the humidity readings…

sorry

what you will need then is a robotic arm that is triggered by the setting sun, and then which moves the temperature sensor out of the bush and back to its normal shelter…and then reverse that process for the day time…
should work OK

otherwise, i think vergil might have a point…

Well I placed my temp sensor in this small bush about a week ago.

I take on board what you say Vergil but it is only a small bush with not much mass. I was more concerned about humidity (from the bush)

The results have been very good, it is not affected in full sun and cools down better at night and has protection from rain.

I previously had it fitted on the front of my garage which was, until mid summer out of the sun all day. But now I realise that there was too much reflected sun related heat from the ground and the house and too much retained heat from the same at night.

This all came to light (no pun) when I fitted my solar sensor which is looking for the difference in temperature. The solar sensor being the opposite, down the garden in the sun away from any buildings.

So the bush may not be perfect but it

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