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  • Replies 23
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Posted
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield
  • Weather Preferences: Any Extreme
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield
    Posted
  • Location: NH7256
  • Weather Preferences: where's my vote?
  • Location: NH7256

    silly me, simper simper. i'll get back in my cave. no, thanks for the links, i'll have to make one myself, the proper freestanding ones are pretty dear. what I was wondering (and should have said at the start) was whether there's a specification for the louvres, or do folk just make them up. thanks all.

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    Posted
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield
  • Weather Preferences: Any Extreme
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield

    probably just as cheap to buy one and have one to the correct specs.

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    Posted
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield
  • Weather Preferences: Any Extreme
  • Location: Sheffield South Yorkshire 160M Powering the Sheffield Shield
    silly me, simper simper. i'll get back in my cave. no, thanks for the links, i'll have to make one myself, the proper freestanding ones are pretty dear. what I was wondering (and should have said at the start) was whether there's a specification for the louvres, or do folk just make them up. thanks all.

    One of those links sells a Kit for £35.00

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    Posted
  • Location: Nr Appleby in Westmorland
  • Location: Nr Appleby in Westmorland

    I don't think there is a standard spec for louvres....it's simply a case of allowing free air flow and keeping the temperature sensor in permanant shade.

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    • 3 months later...
    Posted
  • Location: South Derbyshire nr. Burton on Trent, Midlands, UK: alt 262 feet
  • Weather Preferences: Extreme winter cold,heavy bowing snow,freezing fog.Summer 2012
  • Location: South Derbyshire nr. Burton on Trent, Midlands, UK: alt 262 feet

    Hi everyone,

    Yes to get the most accurate readings you need a Stevenson Screen, i built my own, see-attached picture.

    If you are prepared to spend a bit of time and care, good results can be obtained and save yourself a fortune.

    Paul

    post-1046-1158490542.jpgpost-1046-1158490571.jpg

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    Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

    nice looking bit of kit Paul and I like your UK audio forecast, well presented and very clear.

    John

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    Posted
  • Location: South Derbyshire nr. Burton on Trent, Midlands, UK: alt 262 feet
  • Weather Preferences: Extreme winter cold,heavy bowing snow,freezing fog.Summer 2012
  • Location: South Derbyshire nr. Burton on Trent, Midlands, UK: alt 262 feet
    nice looking bit of kit Paul and I like your UK audio forecast, well presented and very clear.

    John

    Cheers John,

    Yes have only just recently built the Stevenson screen, it was something I have always needed, but the price put me off, £650 to £700 for a standard spec and size.

    In the past I put my sensors in the shade of the house facing North, but I got many temperatures anomalies, especially overnight after a previously hot day, the brickwork from my house acted like a storage heater and gave off artificially high readings, so was constantly having to adjust. The set-up I have now is spot on.

    Thanks for the compliment on my audio forecast, as you must know by the experience Paul and yourself have had with the Net Weather Pod forecasts, they take much longer to prepare than to actually record.

    Regards

    Paul

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    Posted
  • Location: Lincoln, Lincolnshire
  • Weather Preferences: Sunshine, convective precipitation, snow, thunderstorms, "episodic" months.
  • Location: Lincoln, Lincolnshire

    Stevenson Screen? I'm just looking into getting one of those myself. My thermometer is situated on the north-facing side of a hut, and gives accurate readings during the winter half-year but tends to over-read during the summer half-year, especially by day. I do correct for this, but obviously it would be better for accuracy to get accurate readings that don't need any correction.

    The aim is currently to get one made out of a couple of louvred screens attached to a white box, one of which will act as a door- hopefully for a cost of under £10 if I can get away with it.

    Is it true that a Stevenson screen can have louvres at two of the four sides (as appeared to be the case on the screen shown on the BBC weather site), or should it really be louvred at all four sides?

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    Posted
  • Location: South Derbyshire nr. Burton on Trent, Midlands, UK: alt 262 feet
  • Weather Preferences: Extreme winter cold,heavy bowing snow,freezing fog.Summer 2012
  • Location: South Derbyshire nr. Burton on Trent, Midlands, UK: alt 262 feet
    Stevenson Screen? I'm just looking into getting one of those myself. My thermometer is situated on the north-facing side of a hut, and gives accurate readings during the winter half-year but tends to over-read during the summer half-year, especially by day. I do correct for this, but obviously it would be better for accuracy to get accurate readings that don't need any correction.

    The aim is currently to get one made out of a couple of louvred screens attached to a white box, one of which will act as a door- hopefully for a cost of under £10 if I can get away with it.

    Is it true that a Stevenson screen can have louvres at two of the four sides (as appeared to be the case on the screen shown on the BBC weather site), or should it really be louvred at all four sides?

    that looks really good - 'cool' even.

    may i ask - did you make the louvres yourself, or were they salvaged/bought elsewhere?

    Hi TWS, HC,

    I made my screen by copying examples of various pictures and articles downloaded from the internet.

    My Stevenson screen basically consists of 8 louver doors 18”x18” all doubled up and screwed together, (could be glued) bracketed to form a box, one double pair need to be hinged for the door, double plywood base and top, (with spaces to allow further air flow) a supporting post and 4 coats of White paint, that’s 2 undercoats and two gloss.

    The whole lot cost me about £90, It would cost at least £600 for that kind of spec, so a big saving really. I bought all the parts I needed from my local Timber merchants, then you just need a little time and care.

    Hope that helps

    Paul

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    Posted
  • Location: NH7256
  • Weather Preferences: where's my vote?
  • Location: NH7256

    that's great, paul, and the pictures are really helpful. the only snag for me now will be where to put it as my previous chosen location is about to have a plum tree installed!

    anyway, i'm starting to pile up the projects for my new-found leisure time already. certainly one to get sorted out by next spring.

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    • 1 month later...
    Posted
  • Location: Lincoln, Lincolnshire
  • Weather Preferences: Sunshine, convective precipitation, snow, thunderstorms, "episodic" months.
  • Location: Lincoln, Lincolnshire

    I currently have a Stevenson Screen, consisting of 4 louvred sides, a white top and bottom, and which is situated just over 1m above the ground (didn't accurately measure it, but it is close to the standard 1.25m) and next to a fence and away from the house at the side of my back garden.

    The problem I'm getting is that the screen seems to be heating up when the sun shines on it, even though it's white and has louvres at all four sides. Daytime temperatures are massively inflated, but overnight my readings are comparable to nearby official sites.

    I don't know if the sun shining on the solar panel of my AWS might be inflating the temperatures, or if it's a screen problem, but I recorded 18.5C today which is clearly way too high. Anyone got any ideas?

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    Posted
  • Location: Llandysul, Ceredigion, Wales
  • Location: Llandysul, Ceredigion, Wales

    Had a similar problem with my 'knocked together quickly screen' in the summer. This had a back, roof and two sides, but was open at the front (north facing). Hopeing to build a Stevenson screen myself at some point.

    Perhaps you could try a sandwich of insulation on the roof. ie a wedge of insulating foam on top and a water proof top on that.

    The other thing I may do myself is use a computer fan driven by a small solar panel, to ventilate a Stevenson screen 'like' box.

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    Posted
  • Location: Derbyshire Peak District 290 mts. Wind speed 340 mts
  • Weather Preferences: Rain/snow, fog, gales and cold in every season
  • Location: Derbyshire Peak District 290 mts. Wind speed 340 mts
    I currently have a Stevenson Screen, consisting of 4 louvred sides, a white top and bottom, and which is situated just over 1m above the ground (didn't accurately measure it, but it is close to the standard 1.25m) and next to a fence and away from the house at the side of my back garden.

    The problem I'm getting is that the screen seems to be heating up when the sun shines on it, even though it's white and has louvres at all four sides. Daytime temperatures are massively inflated, but overnight my readings are comparable to nearby official sites.

    I don't know if the sun shining on the solar panel of my AWS might be inflating the temperatures, or if it's a screen problem, but I recorded 18.5C today which is clearly way too high. Anyone got any ideas?

    I suspect ,TWS, that your problem may be due to single louvred sides. I remember reading a piece in

    'Weather' a long time ago about comparisons done between screens with single and double louvred sides; the screens with double louvred sides consistently recorded lower temperatures than their single counterparts during warm, sunny weather. The reason for this was the proximity of the the thermometer bulb to the slightly heated louvres during strong sunshine, the double louvres largely eliminated this although on clear, calm sunny days any thermometers enclosed in a screen will tend to record temperatures a little higher than the 'true air temperature'.

    It's also possible that the fence may be heating up in the sunshine and radiating heat into the screen, particularly if the screen is closer to the fence than the height of the fence. Ideally any screen should not be closer to any object than twice the height of the object although this is not often possible to achieve, particularly for amateur observers.

    T.M

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    Posted
  • Location: Lincoln, Lincolnshire
  • Weather Preferences: Sunshine, convective precipitation, snow, thunderstorms, "episodic" months.
  • Location: Lincoln, Lincolnshire

    Thanks for the info.

    I don't think it's the fence, as warming from the fence would cause a steady long-term warming; the readings I'm getting show a rapid rise of 1-2C whenever the sun shines on the screen area, which disappears as soon as the sun stops shining on it.

    My first try will be to cover up the solar panel next to the screen (to see if that's got anything to do that), failing that, I may try sheltering the screen from direct sunlight as installing another set of louvres would be a big pain after the hassle of setting up the original screen. It might come to the latter but I'd rather use that as a last resort.

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    Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

    would agree with what TM says about single v double louvres. Also is the top just a single wood thickness? Have you get any sort of insulation on it? If not this may also aid the higher values when the sun shines on it.

    John

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    Posted
  • Location: South Derbyshire nr. Burton on Trent, Midlands, UK: alt 262 feet
  • Weather Preferences: Extreme winter cold,heavy bowing snow,freezing fog.Summer 2012
  • Location: South Derbyshire nr. Burton on Trent, Midlands, UK: alt 262 feet
    I currently have a Stevenson Screen, consisting of 4 louvred sides, a white top and bottom, and which is situated just over 1m above the ground (didn't accurately measure it, but it is close to the standard 1.25m) and next to a fence and away from the house at the side of my back garden.

    The problem I'm getting is that the screen seems to be heating up when the sun shines on it, even though it's white and has louvres at all four sides. Daytime temperatures are massively inflated, but overnight my readings are comparable to nearby official sites.

    I don't know if the sun shining on the solar panel of my AWS might be inflating the temperatures, or if it's a screen problem, but I recorded 18.5C today which is clearly way too high. Anyone got any ideas?

    Hi TWS,

    Yes I agree with TM and John, for accurate readings the screen does need to have double louvers, the air space between the panels shields against radiation heat and will virtually eliminate temperature anomalies, I am very pleased with my set-up (shown further up in the thread) since installing, the temperature readings from my screen compare very well with official temperature measurements taken in my area.

    Paul

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    Posted
  • Location: Lincoln, Lincolnshire
  • Weather Preferences: Sunshine, convective precipitation, snow, thunderstorms, "episodic" months.
  • Location: Lincoln, Lincolnshire

    I'll look into getting another set of louvres then: better to have something set-up properly, than something set-up but not quite right.

    Thanks a lot for the suggestions.

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