Welcome to the Cumulus Support forum.

Latest Cumulus MX release v3.1.2 build 3055 - 4 November 2019.
Legacy Cumulus 1 release v1.9.4 (build 1099) - 28 November 2014

See the Wiki for downloading either version.

BT's UGLY Fine Offset Rain Gauge Mod

For discussion of DIY weather equipment - sensors, accessories, improvements to existing kit etc
rich27gc
Posts: 72
Joined: Thu 08 Jul 2010 3:15 pm
Weather Station: WeatherDuino Pro2
Operating System: Raspbian
Location: Shap, Cumbria
Contact:

Re: BT's UGLY Fine Offset Rain Gauge Mod

Post by rich27gc » Fri 01 Nov 2013 7:52 am

I can't really see from the picture, but that looks like a wide exit to the funnel, have you restricted it?
I found that I had to reduce the funnel exit to the same size as the original hole in the rain gauge or in heavy rain the buckets got over whelmed.

jim-easterbrook
Posts: 111
Joined: Thu 09 Jul 2009 10:47 am
Weather Station: WH1081, Elecsa AstroTouch 6975
Operating System: openSUSE 13.1, Raspbian, OpenWrt
Location: Epsom, UK
Contact:

Re: BT's UGLY Fine Offset Rain Gauge Mod

Post by jim-easterbrook » Fri 01 Nov 2013 8:22 am

The original rain gauge hole is still there - the new funnel drips onto the original gauge which is unmodified apart from having this monstrosity glued on top. The collecting area has increased by a factor of 2.38 - I never recorded a rain rate anywhere near the claimed maximum so I don't expect any problems from the increased area.
Jim

rich27gc
Posts: 72
Joined: Thu 08 Jul 2010 3:15 pm
Weather Station: WeatherDuino Pro2
Operating System: Raspbian
Location: Shap, Cumbria
Contact:

Re: BT's UGLY Fine Offset Rain Gauge Mod

Post by rich27gc » Fri 01 Nov 2013 9:00 am

I think the increased head of water caused my problem with the water flowing faster from the funnel.
Readings I took before the mod were around 25% under reading, after the mod I have achieved anywhere from 4 to 15% under reading, 15% usually after heavy rain.
Given the price of the whole station I'm quite pleased with the results. There is a Davis station in the same village and that isn't as accurate. :D

AllyCat
Posts: 1060
Joined: Sat 26 Feb 2011 1:58 pm
Weather Station: Fine Offset 1080/1 & 3080
Operating System: Windows XP SP3
Location: SE London

Re: BT's UGLY Fine Offset Rain Gauge Mod

Post by AllyCat » Fri 01 Nov 2013 11:09 am

Hi Jim,
jim-easterbrook wrote:The collecting area has increased by a factor of 2.38
It looks exactly like the "14 cm" funnel that I used for my very similar "temporary" modification two years ago. I couldn't believe it was that far back until I checked my ebay purchase folder. :)

I wasn't sure how to handle the calculation for the flat rim at the top (which at 6 mm represents no less than 16% of the collection area) and I think decided to take the average diameter on the assumption that half the water would splash or drain each to the inside and outside. Is your 2.38 a calculated or calibrated value?

The modification certainly gives much smoother (step-free) rainfall graphs, but I was rather disappointed that it doesn't normally give any earlier warning of "it's raining" because the rain collects in droplets on the funnel (despite its much steeper sides than the FO) before eventually running into the gauge.

I wonder if we can find a paint to kill two (or even 3) birds with one stone? Protect against UV, "hydrophobic" and perhaps a little prettier?

Cheers, Alan.

jim-easterbrook
Posts: 111
Joined: Thu 09 Jul 2009 10:47 am
Weather Station: WH1081, Elecsa AstroTouch 6975
Operating System: openSUSE 13.1, Raspbian, OpenWrt
Location: Epsom, UK
Contact:

Re: BT's UGLY Fine Offset Rain Gauge Mod

Post by jim-easterbrook » Fri 01 Nov 2013 11:31 am

AllyCat wrote:It looks exactly like the "14 cm" funnel that I used for my very similar "temporary" modification two years ago.
That's probably where and when I bought mine. It's been sitting around for a while.
I wasn't sure how to handle the calculation for the flat rim at the top (which at 6 mm represents no less than 16% of the collection area) and I think decided to take the average diameter on the assumption that half the water would splash or drain each to the inside and outside. Is your 2.38 a calculated or calibrated value?
I think I took the approximate inside diameter. The scale factor is a calculation. I don't expect much accuracy from the gauge, before or after fitting the funnel. 16% is neither here nor there.
Jim

User avatar
Buford T. Justice
Posts: 390
Joined: Fri 17 Aug 2012 9:21 pm
Weather Station: Ambient Weather WS-2902A
Operating System: Windows 10 Pro 64-bit
Location: USA

Re: BT's UGLY Fine Offset Rain Gauge Mod

Post by Buford T. Justice » Fri 01 Nov 2013 2:56 pm

Cool. Please keep us posted how it works out. Your funnel looks kind of big though.

On the white one I used, I cut the rim off of it with a pair of scissors going down about 2-3 mm as it was catching too much rain. Now it usually agrees with my Stratus rain gauge, but I am still experimenting with the total size of it. Once I have it just right, I will post a before and after picture.
Last edited by Buford T. Justice on Fri 01 Nov 2013 8:57 pm, edited 2 times in total.

User avatar
duke
Posts: 840
Joined: Sun 03 Jul 2011 6:23 pm
Weather Station: Davis VP2 Plus - 24hr FARS
Operating System: Windows 10 - 64 bit
Location: Eastleigh, Hampshire, UK
Contact:

Re: BT's UGLY Fine Offset Rain Gauge Mod

Post by duke » Fri 01 Nov 2013 6:10 pm

@rich27gc
There is a Davis station in the same village and that isn't as accurate
I'm curious, compared to what???
Duke

Nightingale Weather
Eastleigh, Hampshire, UK
------------------------------------------------------
Validate your pages - often!

rich27gc
Posts: 72
Joined: Thu 08 Jul 2010 3:15 pm
Weather Station: WeatherDuino Pro2
Operating System: Raspbian
Location: Shap, Cumbria
Contact:

Re: BT's UGLY Fine Offset Rain Gauge Mod

Post by rich27gc » Fri 01 Nov 2013 6:21 pm

I know you're going to tell me not to compare two different locations, but it's really isn't that far away from me so I'm comparing it with my ClimeMET manual gauge.

User avatar
duke
Posts: 840
Joined: Sun 03 Jul 2011 6:23 pm
Weather Station: Davis VP2 Plus - 24hr FARS
Operating System: Windows 10 - 64 bit
Location: Eastleigh, Hampshire, UK
Contact:

Re: BT's UGLY Fine Offset Rain Gauge Mod

Post by duke » Fri 01 Nov 2013 6:34 pm

I know you're going to tell me not to compare two different locations,
No actually, I was curious how you were measuring the accuracy of your modification and you answered that too.

As for comparing your station to another station, that 'cannot' be done in my opinion no matter how close. There are just two many variables other than the 'local (in your vicinity)' weather that everybody expects to be the same, it never is, you just don't know why the other station compared may appear more or less accurate, mounting restrictions, poor maintenance etc.....
Duke

Nightingale Weather
Eastleigh, Hampshire, UK
------------------------------------------------------
Validate your pages - often!

jim-easterbrook
Posts: 111
Joined: Thu 09 Jul 2009 10:47 am
Weather Station: WH1081, Elecsa AstroTouch 6975
Operating System: openSUSE 13.1, Raspbian, OpenWrt
Location: Epsom, UK
Contact:

Re: BT's UGLY Fine Offset Rain Gauge Mod

Post by jim-easterbrook » Wed 06 Nov 2013 8:02 am

Blooming thing has stopped registering any rain now. Investigation will have to wait until the weekend.
Jim

User avatar
nitrx
Posts: 1298
Joined: Sun 13 Dec 2009 1:21 pm
Weather Station: WH1080
Operating System: Windows 10
Location: Apeldoorn The Netherlands
Contact:

Re: BT's UGLY Fine Offset Rain Gauge Mod

Post by nitrx » Wed 06 Nov 2013 11:44 am

I followed this discussion with interest but have some questions:

If I make the surface 3 times bigger for collecting the rain I should set the offset of cumulus by the fine offset for rain to 0.33 to get 0.1 mm rain ?

I want also register how long it has rained but I dont know exactly how these times are calculated I read something about it but there will be different methodes. One example was it rains when at least every 10 minutes 0.1 mm rain is registered. The longest raintime in the Netherlands is about 26 hours.

Ofcourse I know it's impossible to get exact values with a fine offset but 1 mm or 10 mm doesn't say all about the experience how wet a day was a strong thunderstom of 10 minutes can give 10 mm in 15 minutes and it can be nice waether for the rest of the day but a drizzle day can give 3 mm and will go in the books as a 'bad' day.

User avatar
Buford T. Justice
Posts: 390
Joined: Fri 17 Aug 2012 9:21 pm
Weather Station: Ambient Weather WS-2902A
Operating System: Windows 10 Pro 64-bit
Location: USA

Re: BT's UGLY Fine Offset Rain Gauge Mod

Post by Buford T. Justice » Wed 06 Nov 2013 2:25 pm

I cannot answer all your questions. My entire goal with this mod was to get close to my Stratus rain gauge which the CoCoRaHS network observers use here in the USA without modifying Cumulus settings. I said in a few posts earlier I had cut down the funnel I am using. I am now a little under what the Stratus is showing so I need to get a new funnel, cut it down a little, and keep it bigger than what I have now slightly. I did figure out I got it from Walmart a long time ago. They still sell it along with a bigger funnel:

http://www.walmart.com/ip/Mainstays-2pc ... t/17188380

I think it is the smaller 8 oz. funnel I am using.

AllyCat
Posts: 1060
Joined: Sat 26 Feb 2011 1:58 pm
Weather Station: Fine Offset 1080/1 & 3080
Operating System: Windows XP SP3
Location: SE London

Re: BT's UGLY Fine Offset Rain Gauge Mod

Post by AllyCat » Wed 06 Nov 2013 3:30 pm

Hi Ron,
nitrx wrote:If I make the surface 3 times bigger for collecting the rain I should set the offset of cumulus by the fine offset for rain to 0.33 to get 0.1 mm rain ?
Not quite, you should set the multiplier in Cumulus calibration to 0.33. That will make each "tip" of the rain gauge show as 0.1 mm. One of the reasons for increasing the collection area is that I believe that less than 0.2 mm is considered as a "dry" day (or recorded as "trace"), so a 0.3 mm tip resolution is not really adequate.
nitrx wrote:...a strong thunderstom of 10 minutes can give 10 mm in 15 minutes and it can be nice waether for the rest of the day but a drizzle day can give 3 mm and will go in the books as a 'bad' day.
10 mm in 15 minutes will probably show as a "record" of 40 mm/hour rain rate in the Cumulus (all time) logs! But to check back for "unusual" data that is not normally reported by Cumulus, you could look at the "Select a Graph" for any period of time, or "post process" the Cumulus files with a Spreadsheet program such as Excel.

Cheers, Alan.

User avatar
nitrx
Posts: 1298
Joined: Sun 13 Dec 2009 1:21 pm
Weather Station: WH1080
Operating System: Windows 10
Location: Apeldoorn The Netherlands
Contact:

Re: BT's UGLY Fine Offset Rain Gauge Mod

Post by nitrx » Wed 06 Nov 2013 5:02 pm

Alan thank for pointing out the multiplier.

I've had pourdown of 111,6 mm/hr intensity but I'm interested in how long it has rained on a day I think a database or excel will help.

Ron

darren
Posts: 13
Joined: Wed 06 Nov 2013 11:24 pm
Weather Station: Davis Vantage Pro 2
Operating System: Windows 10
Location: Stockton on Tees UK
Contact:

Re: BT's UGLY Fine Offset Rain Gauge Mod

Post by darren » Thu 07 Nov 2013 11:46 pm

If you were bothered about making it prettier. How about using a plastic lid fromsomething, a piece of wood or upvc. Slightly larger all round, a hole in the middle for the pipe, sit it on top, turn it all over, hot glue or other adhesive all around the underside to attach it to the rain gauge, turn it back over then the same around the pipe where it sticks through?

Post Reply