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Re: STEVENSON SCREENS - CHEAP OPTION

Posted: Wed 09 Jul 2014 3:13 pm
by Repairman77
This is yesterdays and today's figures for your interest...

Re: STEVENSON SCREENS - CHEAP OPTION

Posted: Thu 10 Jul 2014 12:36 pm
by BillW
Hi All,

I also built an instrument screen out of louvred cupboard panels but it's only lasted a few years. After reading the posts here I tried to get one of these lantern holders too but to no avail.

Much to my surprise the weather here has been really good, wall to wall sunshine and temps in the 20-22 C range for the past week. So as I have been on holiday I thought a good project would be to make another screen.

Given the price of these latern holders I tried to match that by using as much scrap wood as I had lying around from other household diy and repairs. So far I've only had to but one piece of wood and a tin of paint. As I'm no carpenter and not having a router making the louvered panels was pretty much a slog of lots of little spacers held together with wood glue and small nails.

Here are the results so far. A final overcoat will go on tomorrow and then I'll need to knock up some sort of holder for the solar panel that will power the aspiration fan. It actually looks pretty good in the picture but a lick of paint has hidden a multitude of sins!!! ;)

cheers,
Bill.

Re: STEVENSON SCREENS - CHEAP OPTION

Posted: Thu 10 Jul 2014 12:55 pm
by Repairman77
Well done Bill; it looks very smart. I did consider making one from scratch myself but with only a limited amount of woodworking tools I decided against it; it looked like too much work for me. I had constructed my previous one from small ready made panels which seemed difficult and expensive to obtain nowadays, so was delighted to find the lantern boxes available at a very reasonable price especially as I didn't need such a large one as previous as it didn't have to house the old Thermo-Hydrograph pen recorder that I previously used.

I'm not sure how long the lantern box will last but it has a couple of coats of yacht varnish over the paint so it should last several years.

Good luck with your latest construction; perhaps you could post a picture when it is finished showing it's contents.

Mike.

Re: STEVENSON SCREENS - CHEAP OPTION

Posted: Thu 10 Jul 2014 2:49 pm
by BillW
Hi Mike,
Thanks, now it's nearing completion it's looking better than it did. It was a lot of work sawing all the small spacers, pretty boring really. However with the decent weather it's been nice to plod on in the sunshine :D

I'll post a pic when it's done and in place. The old one currently houses a Max/Min, Masons Hydrograph, and the electronic sensor for the PWS.
Cheers,
Bill.

Re: STEVENSON SCREENS - CHEAP OPTION

Posted: Thu 17 Jul 2014 2:38 pm
by callum91
That looks very good Bill!

I'd definitely agree with putting a fan in it. Today has been a typical day when an aspirated screen would certainly improve accuracy (very little wind and high temperatures). Mine is the small lantern type screen without a fan so today I've had to resort to using an aspirated psychrometer to get accurate readings.

Re: STEVENSON SCREENS - CHEAP OPTION

Posted: Mon 21 Jul 2014 6:29 pm
by BillW
Hi,
Turned out to be not so cheap after all.... :(
The bit of ply I had used on the base and for the outer roof was rotten. The electric screwdriver I used pushed the screws right through to the frame. The cost of a new bit of ply instantly doubled the price. Didn't break the bank so back to cutting and painting. I'm actually surprised the effort it has taken! I now appreciate why the proper ones cost so much, even just filling time on a few days holiday adds up to a lot of hours all in (...and it's still not fully finished! :shock: )
Anyway, drum roll please as it has been put on the stand and instrumented up...



I've put in some small blocks that will be used to mount an inner screen to fully shield the thermometers and the battery/charge controller will be put in a box underneath at the bottom of the stand. The "flow director" will eventually be painted and properly attached once the inner screen is in place. (Thats for next years summer holiday, I'll live with it for the time being! ;) )

Be interesting to see how it compares with the other sensor I have on the fence. I suggested putting it in the middle of the garden but you can guess the response... :lol:

I can finally relax on my last day off and have a beer in the sun :D

cheers,
Bill.

Re: STEVENSON SCREENS - CHEAP OPTION

Posted: Sun 03 Aug 2014 10:49 am
by jrhilton
Hi Bill, in your first image I can see what looks like a rainwise rain guage over a gill screen on a metal plate fixing. How does your new screen compare to this in terms of max/min readings?

What was the reason for building a new one as I would have thought the gill screen would be ideal - though looking at your pictures i'm wondering if it is because the gill didn't fit all of your sensors?

Re: STEVENSON SCREENS - CHEAP OPTION

Posted: Sun 03 Aug 2014 3:13 pm
by BillW
Hi,

The unit on the fence is a Peetbros "Sensor Combo" as they call it.
Went wired due to being fed up with radio link drop outs. It's a fixed assembly inasmuch as it's built to accomodate their own temp/hygro box. Not really meant for anything else.
The fan in the wooden screen makes a difference on the few days it's been sunny since finishing the outer box.
cheers,
Bill.

Re: STEVENSON SCREENS - CHEAP OPTION

Posted: Sun 16 Nov 2014 9:24 pm
by dc1500
This is mine. Made a few years back using Wickes(UK) builders merchant plastic louvre panels which were only a few pounds for 4. I found they left a small gap that the low sun could get through on the Western side elevating the temp by about 1C.
http://www.laindonweather.co.uk/images2/Thumbnails.html

Click on Stevenson Screen

Re: STEVENSON SCREENS - CHEAP OPTION

Posted: Mon 03 Aug 2015 11:51 am
by Repairman77
Thought I'd just pop back in again since I started this article around 20 months ago and give an update.

The main structure does seem to be sound although the base separated from the main carcass which looks like a failure of the glue, the base being plastic laminate (like gutter boards stuff) and the rest wood. Easily fixed. No idea how long it will last but if it's lasted 20 months in all weathers there's hop for a few more years. Such a pity they don't make a cheap plastic louvred box, but guess there's such a small market there wouldn't any profit in it due to tooling costs.

Mike.

Re: STEVENSON SCREENS - CHEAP OPTION

Posted: Sat 30 Jan 2016 2:09 pm
by Repairman77
UPDATE...

Well it's now 2 years since it was installed and it has taken a bit of wear over that time. It has twisted a little vertically but is in one piece and still, at the moment, serves it's purpose.
It may last a few more years hopefully before it disintegrates.
I haven't come across anything suitable made of plastic at an affordable price yet but will keep looking. The proper Stevenson screens are an horrendous price for us amateurs and rarely seen second hand.

Will keep you updated should it decide to give up the ghost.

Mike.

Re: STEVENSON SCREENS - CHEAP OPTION

Posted: Wed 18 Jan 2017 12:54 pm
by ray951
How about purchasing an Ambient Weather SRS100LX Temperature and Humidity Solar Radiation Shield.

One on ebay http://www.ebay.co.uk/itm/222378751843? ... 1555.l2649

Re: STEVENSON SCREENS - CHEAP OPTION

Posted: Fri 09 Feb 2018 1:33 am
by Wayoz
I did several experiments many years (decades actually) ago and found that I could not make anything with single louvres work properly. Even with the louvres angled steeply down, there was too much radiation getting into the box which, on a still, sunny day, would result in readings 3-5 degrees too high.

The final prototype was made with eight louvered panels from a local hardware store so that each side had two panels with the louvres in opposite directions (down on the outside and down when viewed from the inside). This was tested alongside a disused met bureau screen over a period of a month and the variance between the thermometers in each screen was indistinguishable from the same two thermometers in the official screen.

My latest screen uses the same technique made from old house shutters cut to size with a circular saw and it functions perfectly. As a comparison, I once placed another sensor in one of those tiny 'stack of plates' type enclosures which came with the automatic station. The result was way off compared with my home-made screen (3-5 degrees too high on a sunny day).