modify bucket to 0.1mm

I assumed you meant 374.4mm/hr as recorded in WD, which the console would (if it could) see as 3744mm/hr (because the console thinks that every tip represents a mm, whereas WD has been told that it’s only 0.1mm).

Or did you mean something else?

Strange.
Just to be sure - is this “Maximum rain rate” on the main WD screen we are talking about, or “All time records”, or both?

Its just my maths is all, never been any good at it lol but this is what i worked it out at;

to get 374 in WD would be 374 x 0.104 = 38.896mm on the console but like i said my maths
are totally pants, when it comes to decimals “i am NOT smarter than a 10 year old” lol

But yes WD all time record said 374.4 mm/hour but now it only says 372.0 mm/hour, surely this
is an impossibility? how can the maximum all time be recorded as 372 when an hour or so it was
374.4??

BOTH

Other way around.

The console knows nothing about the funnel, so it still thinks that every tip is 1mm.

WD knows that each tip is really 0.104mm

So the console thinks there is (approx) 10 times more rain than there really is.

Does that make sense?

No idea… :?

Yeah that makes more sense lol, told you i was a thicket pmsl…

Baffling on the all time record though, another gremlin me thinks?

You can’t calculate the funnel diameter for a particular tip size without referencing the original tip size in the calculation.

The math is incorrect:

For a 0.1mm tip resolution(ROC) your Funnel Size(MFS) would be: = 1000 mm (100cm funnel diameter)

For a 0.2mm tip resolution(ROC) your Funnel Size(MFS) would be:
= 500 mm (50 cm funnel diameter)

The tip size depends on the area of the funnel, not the diameter. If the diameter is halved, the area is reduced to one quarter of the original area / or the tip size increased to four times the original.

Hmmm … now what on earth was I thinking there?
Must be the late nights that got to me.
Any case here is the corrected version (I’ve deleted the old).


I think a good starting point for determining the funnel size for your rain gauge would be to first look up your all-time recorded [b]mm/h Rain Rate[/b]. Then you can calculate your max [b]bucket/funnel size[/b] as follows:
[b]ASSUMPTIONS (WMR200):[/b] `[b][color=red]RGR[/color][/b] = 999 mm/h ... rain gauge max resolution =

Better :smiley:

But:

For a 0.1mm tip resolution(ROC) your Funnel Size(MFS) would be: MFS = RGD / sqrt(ROC) = 100 / sqrt(0.1) = 100 / 0.3162278 = 316.23 mm

That’s only valid if the original tip size is 1mm.

Or you could just use my online calculator.

Isn’t the tip(per) size (tipper quantity) irrelevant?
If I double the surface area on the rain gauge then sure I get double the water pouring through the funnel.
In other words it’ll tip twice instead of once for the same rain rate.
if 1mm of rain falls over a surface area of 100mm2 that would be: 1001 = 100ml
if 1mm of rain falls over a surface area of 200mm2 that would be: 200
1 = 200ml
So I would have to adjust the WD resolution to 0.5 i.e. for every tip only count half the quantity.
That’s how I understand it from the WD setup below:

So if my tipper catches 2ml per tip and I double the surface area on the rain guage
the tipper is catching double the amount of water i.e. it will tip twice: 22ml = 4ml.
Therefore WD must only record half of it (4ml
0.5 = 2ml).

Am I missing something here?

By the way I did some tipping on my rain guage (WMR200) and I’m get conflicting reports from the console, the WMR gatherer and WD logs.
`------------ ----- ----- ----- -----
Time of tip> 14h30 15h16 17h30 TOTAL


WMR Console 1.1mm 1.0mm 1.1mm 3.2mm
WMR Gatherer 9.7 10.8 11.8 ?
WD Log 1.3mm 1.1mm 1.0mm 3.4mm`


The previous record in the log on the 4Feb2009 @ 16h55 recoded 0.7mm.
No other rain for the day. I also see some tips of 0.8mm in the logs.

Now I wonder what my tip size is.
Is WD making it’s own rain or did I mess up a configuration somewhere.

The relationship is correct, if you increase the area 10x, you will reduce the tip to 1/10 of the original value - no argument there. But what you are missing is that you would only end up with a 0.1 mm tip, if you start with a gauge with a 1 mm tip and different brands and models of gauges have different tip sizes. If you 10x’d the area of a standard Davis gauge (which I wouldn’r recommend) you would end up with a 0.001 inch tip for instance.

Aha, I get it :smiley:
If your tip size is 2ml and you want to bring it down to 0.5ml per tip then it would be 4x more accurate.
Which means a correction of 0.25 in WD.

Do you really get inaccurate rain gauges like that?

Hi guys, i have had to add a new funnel @ 280mm diameter i think i got the correct setting for WD but could someone
please confirm it is 0.032 please cause i aint sure if it is recording the rain correctly?

Or is it 0.128 ?

According to my calculations, the new setting in WD will be 0.128 mm for a funnel of diameter 280mm.

I use the calculations:-

OSI Rain Gauge I/D =	100mm	Area =  7853.981	mm2
					
New funnel I/D =	280mm	Area =	61575.216	mm2
					
Area increase =	7.84	(New funnel area / original area)
					
Rain gauge original tip =	 1	mm
					
So new tip =  0.12755102	mm	(original tip / area increase)

Hope it helps,
Ian

I agree :smiley:

Thanks a lot Ian, so glad i rechecked it, that will explain why the rain amounts were off

Thanks for the concurrence Niko :wink:

Hey Niko, just to let you know, i have been using the 0.1mm for years now with no issues at all, never hit the limit on the console
I have even had torrential rain a good few times, it works flawlessly :slight_smile: I was surprised that it worked so well, like ya said, i have gone
from a larger coffee mug to a reasonable sized kitchen bowl lol :slight_smile:

Thanks to all the above: required reading for those who are fed up with 1 mm tip on 100 mm gauge.

I went for a 200 mm funnel to bring the modified tip down to 0.25 mm (cp European Davis 0.2 mm) and it worked beautifully today: OS console 44.2 mm, WD shows 11.1 mm, CoCoRaHS 11.2 mm. (Good vertical rain for checking, not much wind.)

P.S. OS WMR200 manual says the rain gauge can handle 9999 mm/hr: I make that 2.78 tips/second (and I don’t believe it - I think they mean the console display!).

I went through the comments, and unless I missed something, while there is an allusion to WD settings, is there a place in WD setup or offsets or something, to modify the incoming tips to read out as a corrected value.

That is, if the tipper is off and reports 1.34 " of rain, when it really is 1.27, can one correct it with a WD setting? Where if so?
Thanks, Dale

Control Panel → Offsets and Initial Rain → Rain Offset.

Thank you. The excuse I have is looking right at it and not knowing what it would do, and to that degree.

Thanks again, I learn something every day, and at times, every minute!
Dale