Idea for radiation screen/shield

Originally, I posted the following on the WeatherFlow thread relating to radiation screens/shields/Stevenson, but it has a much wider use than just for a specific hardware, therefore I’m re-posting it as a general idea for all weather systems.

I’m surprised that there is little available between these cheapo stacked saucer types and a true Stevenson screen. I’m sure there must be a world market for a robust moulded device in white UPVC, probably stacked and clicking together (no long threaded rods), with dual louvres and enough space for all types of sensor, say internal 8x8x25 to 10x10x30 cm (room without touching sides). Target selling price <

10x10x30 - is that 30 wide or 30 high?

30 cm high. Could be 10 dia and 30 high.

(Slightly relevant to the thread, I slipped my aluminium-foil coated plant saucers from previous threads over the Aercus sensor. Is reading about 0.8

I’m not in your targeted demographic but if I did build one for my sensor experimental purposes I would be aiming for more of a cubic interior space. Maybe 20 x 20 x 20 or 20 dia x 20 high cylinder. Incidentally a cylinder with equal diameter and height has the least surface area for any given volume, which may be worth to consider - except for the limitation of accomodating existing packaged sensors.

BTW, how are double louvers configured? Is it a stack of V shaped sections, or are they offset/staggered vertically?

I don’t think they are inverted V-shaped sections: I think there is some horizontal separation between panels but no vertical offset, if that makes sense. Can someone with a genuine screen chip in and tell us?

Double louvres are important, though, for those of us who may get solar reflection from below the horizontal.

Found a diagram from MetSpec UK their shield is built up of alternating white and black “rings” with louver overlap. That’s a complicated bit of tooling…

…and a cutaway picture here, page 2.

Impressive, but only handles “probes” up to 25 mm. OK if you can afford a PRT. But I think you got to the nub, niko, for most of us: “the limitation of accomodating existing packaged sensors”. My OS sensors are 92 x 60 x 20 mm, and the AIR unit is a lot bigger than that.

hi

see images, this is what I came up with
could be made larger

Solar radiation aspirated shield project

http://www.weather-above.com/solarrdscreen2.html
update
update
hi everyone

been in Wales for 5 weeks, weather very hot

I was thinking about my home made solar aspirated
Shield, I used spray insulating foam in the wall of the shield, it works well but it’s very messy to use so I come up with an alternative

I made another solar aspirated Shield everything has the same specification as the first version but instead of using the spray insulating foam

I made a solar blocking membrane, this consists of a very thin foam membrane in between aluminium foil sheets

this technique is more friendly to use

the inner wall now as 2 solar blocking membrane tubes one inside another , this has made my solar aspirated
more friendly to make, will soon update my Web page
on how to make the solar blocking membrane

mick


5a aspirated solar radiation screen by Michael Parry-Thomas.jpg

That’s a good point too. In some ways constructing a good aspirated shield is a lot easier than a good non-aspirated one.

I’m still thinking about screens/shields. I attach a temp chart as measured today. Note that the two sensors are several metres apart under different conditions, so that the absolute values are not necessarily very meaningful. The Davis is a standard unaspirated shield; the Aercus has my aluminium foil coated ‘pagoda’. I think the differences between the two lines are meaningful. The first point that I believe is significant is yesterday from about 13:00 to 18:30: the Davis screen indicates higher temperatures due to the sun shining directly on it. This is in line with other observations that the passive Davis reads high with direct sunlight on it. (Wait until we reach 40+


I’m not a Davis disciple but it really sounds as if FARS would help. . . Could you retrofit?

Even with the UK spec, it still does not produce accurate temps in low wind scenarios, i believe they state that somewhere. The best you can achieve is as close to the air temp as you can afford to build, it will never be spot on because there is no real accurate temp to compare against, your property is not the same as the official station and its no doubt at least a mile away.

A reasonable shield under

While I agree with the original idea, I’d like to say that a home-made wooden house is great (and cheap!). I have 3 stations: Irox type, WH-3081 and Davis VP2. Davis is in its proprietary shield located 1 meter away from the wooden house. One can see a constant offset of 0.6 degC under all conditions (night, full sun). That is the property of the sensors. When the sun comes up (starting at -10 degC during winter morning) a sensor in the wooden house tends to raise quicker than the Davis. But they meet at 0.6 degC offset sooner or later.

I was looking for a good shield for other sensors but there is not much choice. I’ll put the upcoming WF Air into a wooden house :slight_smile: