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Making a Stevenson Box


PlantPot

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Posted
  • Location: Kelso, Scottish Borders
  • Location: Kelso, Scottish Borders

Found a couple of white plastic louve vents in a skip today and thought DIY stevenson screen.

 

Would the internal sizes of 110mm square by 180mm deep be big enough for a small probe ?

 

Could the top be 18mm thick wood painted white, or does it need some sort of two layer top.?

 

Can the bottom be left open ?

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Posted
  • Location: Derbyshire Peak District. 290 mts a.s.l.
  • Weather Preferences: Anything extreme
  • Location: Derbyshire Peak District. 290 mts a.s.l.

Found a couple of white plastic louve vents in a skip today and thought DIY stevenson screen.

 

Would the internal sizes of 110mm square by 180mm deep be big enough for a small probe ?

 

Could the top be 18mm thick wood painted white, or does it need some sort of two layer top.?

 

Can the bottom be left open ?

The dimensions sound adequate for a sensor but double louvred is better than single.

A double layered top is also recommended; the top layer can be a solid piece of wood painted gloss white while  the second layer should have air spaces  in it.  You'll also need a bottom to it, also painted gloss white and with air spaces, to prevent excess secondary radiation from the ground beneath. 

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Posted
  • Location: Kelso, Scottish Borders
  • Location: Kelso, Scottish Borders

have now made it up and quite pleased how it looks, BUT - its not working, in bright sunshine it is reading about 1.5 degrees too high - any thoughts on how to improve it ?

 

couple of pictures showing the box and its position (the fence runs nearly north south and it is on the south side. so open sunshine from east south and west)

stevensonbox_0314_zps2388ac10.jpg

 

stevensonpos_0317_zpscea57056.jpg

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Posted
  • Location: Chelmsford, Essex
  • Location: Chelmsford, Essex

I've had my sensors in shade provided by a tree because I never had a proper screen/box. I realised it was probably too shady - i.e. it wasn't representative of most of my garden because no sun was getting to the area where my sensor was.

 

I thought I'd have a go at making my own box, using a design on the internet, to see if I could place the box in direct sunlight. It's made of wood and looks very similar to yours, and like you I found the readings were 'spiking' when the sun came out and were obviously too high.

 

In the end  I placed the whole box in an area which is still slightly shaded by the tree but the whole area does get some direct sunlight (it just doesn't hit my box). This has done the trick - the box does its job as it's shading the sensor from heat being reflected from other surfaces, but it's more representative of the actual temperature in my garden.

 

I'm not convinced any DIY screens/boxes are up to the trick  to provide a shield from direct sunlight, so my advice would be to place your whole box in an area that is partially shaded from direct sunlight (I know some would probably disagree with me though!).

Edited by h2005uk
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Posted
  • Location: Chelmsford, Essex
  • Location: Chelmsford, Essex

By the way here's my box:

 

b5OZKRxl.jpgc86VKmul.jpg

 

I've since painted the inside of the box black to further help. The design I based it on is here (I added the plastic louvres and increased the dimensions a bit): http://www.weatherforschools.me.uk/docs/weather_box_digital.pdf

 

Just a note on shade provided by vegetation - the downside can be that natural processes (e.g. evapotranspiration) can cause cooler temperatures in the day and warmer temperatures at night next to the vegetation, but I've not found that to be the case as my readings are quite similar to official stations in the area. I suppose it depends on the extent of the vegetation though.

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Posted
  • Location: Kelso, Scottish Borders
  • Location: Kelso, Scottish Borders

I noticed a problem with mine today and wondered how yours compares.

The plastic that makes up the louves on mine is semi transparent, looking from the inside when the sun is shining, Ii i place a finger on the "Sun Side" I can clearly make out my finger - I imagine this is a problem - what do others think ?

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Posted
  • Location: Derbyshire Peak District. 290 mts a.s.l.
  • Weather Preferences: Anything extreme
  • Location: Derbyshire Peak District. 290 mts a.s.l.

I noticed a problem with mine today and wondered how yours compares.

The plastic that makes up the louves on mine is semi transparent, looking from the inside when the sun is shining, Ii i place a finger on the "Sun Side" I can clearly make out my finger - I imagine this is a problem - what do others think ?

It will be a problem as, if you can see your finger through the plastic, a certain amount of solar radiation will be entering the screen; probably as much as if you'd made it from frosted glass.

It's one reason why double louvres are better than single but, ideally, even a single louvre should be completely opaque. 

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Posted
  • Location: Penrith Cumbria
  • Weather Preferences: Cold, snowy winters and warm sunny summers
  • Location: Penrith Cumbria

I noticed a problem with mine today and wondered how yours compares.

The plastic that makes up the louves on mine is semi transparent, looking from the inside when the sun is shining, Ii i place a finger on the "Sun Side" I can clearly make out my finger - I imagine this is a problem - what do others think ?

You are much better using wood as it's thermal qualities are better and you can paint it a brilliant gloss white which is best.

I have created a double skinned wooden box with holes drilled at 45 degree angles every 2 cms so air can flow freely but no sun, indeed very little light enters the box. This works really well and my readings correlate well with those from the nearby MetO station.

My main problem is my medium sized garden so things like fences and patios heat up in summer on hot days which isn't ideal but the box itself works just fine.

Andy

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