Cleaning Davis Vantage Vue

[Jack Harrison]

I am about to advertise my stupidity.

 

I was not getting any temperature readings until there was enough daylight for the solar panel.  So new battery fitted.  I presume all will be well overnight and readings will continue.

 

I can’t recall when I last cleaned the Davis.  It could well have been when I moved here in summer 2015.  Today when I took things apart, I was appalled how much dirt and rubbish had accumulated – even some little insect grubs.  The tipping bucket (spoon) wasn’t too bad but even the tiny amount of residual dirt must have meant that it tipped each time too early resulting in over-reading rainfall totals.  I could work out the approximate error based on volume and mass of rain equivalent to 0.2mm rainfall.  But I would have to take the Davis down again and measure the size of the bucket:  I can’t be bothered.  Even if I did, the calculated error would be very approximate.  My guess is that it is under 5%.

 

During the cleaning process, the wireless signals were still being sent including 0.2 mm “rain” every time I tipped the bucket (spoon).  So 1.6 mms rain has been “recorded” on a [so far] totally dry day!

 

It’s working again and data seems reasonable by comparison with nearby Inverness and Kinloss.  However, the wind direction is – as ever – more or less meaningless.

 

The lesson:  clean it more often, perhaps every six months.  How often do others clean out their Davises?

 

Jack

[Brian Wakem]

First thing I do before doing anything to my VP2 is disconnect the 'Rain' wire.  I've only cleaned mine twice in 4yrs, apart from tree debris in the rain collector which I clear almost weekly.  Both cleans coincided with fan failure so I had it apart anyway. 

[Jack Harrison]

...disconnect the 'Rain' wire.

Sounds sensible but is it obvious how to do that?  (Can't look as mine is back up on its pole).

Jack

[Brian Wakem]

On a VP2 it is obvious, one of them is labelled rain.

[Trevor Harley]

You have made me think that I haven't cleaned mine anywhere near enough. Usually when I think something might be going wrong. I do poke something through the rain gauge hole occasionally though.

I will do it as soon as it gets light again (March).

Trevor

[George in Edinburgh]

Cleared a rain collector blockage recently with a cocktail stick and recorded what was probably the world's highest rainfall rate. Now, editing/deleting local records on Weatherlink is straightforward but if the data has slipped through on Weatherlink.com then that's it as far I can see. It's in cyberspace for ever. As Brian says the way to do it is to disconnect the 'rain' lead.
I get far more crud in the rain collector here  than was ever the case in Epping. Not sure if this if flora, fauna or both. Also noticed that the Stevenson Screen needs a clean, inside and out.

George in Swanston, Edinburgh
www.swanstonweather.co.uk

[Jack Harrison]

On a VP2 it is obvious, one of them is labelled rain.

I must have a different version - mine looks nothing like that.

Jack

[xmetman]

You are a bit closer to auld reekie!

[Keith (Southend)]

I love it when the consoles ticker line comes up with "It's raining cats and dogs" :-)

My biggest problem with the raingauge(s) are cobwebs/spiders.

Keith (Southend)

[Jack Harrison]

Thanks to some good advice, especially from George, my sparkling clean Vantage Vue now records wind direction with some vague degree of “truth”.  But I’m not sure that the speed reading is correct.  The anemometer has been spinning like crazy today yet the current speed is given as a mere 7 knots.  I understand of course that being inland it is not fair to make direct comparisons with coastal stations nearby - Inverness, Kinloss and Lossiemouth - yet all those airfields are showing in excess of 20 knots.  There is a mountain wave effect here which might be influencing the local wind speed.  So the readings I am seeing are not necessarily wrong although there does remain a suspicion.

Is there any way of confirming the validity or otherwise of the speed reading from my Davis?

Jack

[Brian Wakem]

Buy a cheap-ish hand-held anemometer and test it that way.  My peak gust speeds in any storm are always about half that recorded at local airfields (Odiham & Farnborough) despite my anemometer being around 11m above ground.  Unless you are surrounds by hundreds of metres of open countryside you have no chance of recording decent wind speeds.

[Jack Harrison]

Buy a cheap-ish hand-held anemometer

 

Oh dear, I hadn't thought of that.  I already have a hand held anemometer that has been been [roughly] tested in calm winds against speed of car (held out of window).
Next problem - where is it in my collection of (normally) useless toys?  I think I know where it is - job for the morning to locate.

Jack

[Jack Harrison]

The wind vane has fallen off again.  I give up.  It wasn't very useful in any case.

Jack

[Trevor Harley]

Mine isn't that useful either. It's difficult to get it up (so smirking please) high enough.

Also it's very difficult to get the rain gauge suitable exposed and level, so I'm sure mine under-records, particularly in heavy rain.

And even with screen clean the thermometer seems to over-record on sunny mornings, presumably because it's not over exposed short grass.

And the humidity meter never goes above 92%, no matter how dense the fog.

On the whole I wonder why I bother.

[Jack Harrison]

Trevor says: it's very difficult to get the rain gauge suitable exposed and level

Obviously it is ideal to be horizontal, but the maths would show that a few degrees of tilt would not significantly affect the catchment area (an almost circular ellipse - versus a true circle).

As for potential under-reading due to tilt, I would have thought that unlikely to be significant - unless the rain is so intense that the funnel overflows!  Maybe wind could blow away some of the rain (?)

Over to George who has a weather station approved by the Met Office (I am right aren't I George?) for official recording.  (Mine is purely for "hobby" interest).

Jack

[Keith (Southend)]

I rarely get above 38mph for wind speeds and I know at Southend Airport gusts can be considerably higher, and the weather station there is less than a mile from me. I can't get my anemometer(s) any higher than they are. I also locate my R&D Sun dial up the pole  and I tend to get considerably longer hours of sunshine that Shoeburyness (03693), which I know is fairly sheltered and I think has a sea wall to the west of the site, which is actually nearer Great Wakering than Shoeburyness, so probably loses the last of the afternoon sun.

See picture of the three units...

http://www.southendweather.net/anemometer2.jpg

Keith (Southend)

[Jack Harrison]

hand held anemometer....Next problem - where is it in my collection of (normally) useless toys?  

I eventually found it (Technoline EA-3010) after a rummage through the toy cupboard.  But of course, the battery is flat.  Replacement battery due Wednesday.

Jack

[George in Edinburgh]

I have a standard rain gauge courtesy of SEPA with daily readings sent to SEPA/UKMO. It is checked every 2 years by UKMO (a chap from Eskdalemuir). The rest of the equipment is VP2 (including solar rad sensor and daytime FARS), RD sun sensor, traditional thermometers (mostly) in a Stevenson Screen. Parts of the screen are 57 years old-it was bought as a kit from Casella in Fitzroy Square, London. Apart from the standard rain gauge nothing is approved as such. The anemometer and sunshine sensor  are on a long pole at a gable end so I get good wind and sunshine readings.
There have been many discussions (here and usw) over the years about the merits or otherwise of TBR gauges. I treat these readings as of value in the timing of events and an idea of intensity. Actual quantities are from the standard gauge.

Now, no one mention the football.