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Rain Gauge Funnel Multiplier

For discussion of DIY weather equipment - sensors, accessories, improvements to existing kit etc
Mark19
Posts: 17
Joined: Thu Jan 28, 2010 7:53 pm
Weather Station: W-8681 (WH-1080)
Operating System: Windows 7
Location: Carnkie, Helston, Cornwall
Contact:

Rain Gauge Funnel Multiplier

Postby Mark19 » Tue Oct 19, 2010 6:13 pm

Hi,
I have just added a bigger funnel to my W-8681 rain gauge, and now I need to know what the multiplier should be.
My funnel has a diameter of 18cm, so I have worked out the area is 283cm squared. How would I go about working out the new multiplier?

Thanks,
Mark
Carnkie Weather Station & Webcam: http://carnkieweather.co.uk
Live from Carnkie, Nr Helston, Cornwall.

Gina
Posts: 1885
Joined: Sat Feb 21, 2009 12:41 pm
Weather Station: Nothing working ATM - making one
Operating System: OS X, Linux Mint, Win7 & XP
Location: Devon UK

Re: Rain Gauge Funnel Multiplier

Postby Gina » Tue Oct 19, 2010 6:29 pm

The area of the original rain gauge is 55 sq. cm. so the correction is 55 divided by your new funnel area.

Diameter = 18cm Radius = 9cm r2 = 81 - multiply this by Pi (3.142) gives 254.5 sq. cm. So the ratio is 4.627 (254.5/55) and the correction factor (multiplier) is the inverse of this = 0.216. Actually 55/254.5 ie. old/new catchment area.
Gina

Sorry, no banner - weather station out of action. Hoping to be up and running with a new home-made one soon.

Mark19
Posts: 17
Joined: Thu Jan 28, 2010 7:53 pm
Weather Station: W-8681 (WH-1080)
Operating System: Windows 7
Location: Carnkie, Helston, Cornwall
Contact:

Re: Rain Gauge Funnel Multiplier

Postby Mark19 » Tue Oct 19, 2010 6:36 pm

Thanks alot for that Gina. I never would have worked that out. :lol:
Carnkie Weather Station & Webcam: http://carnkieweather.co.uk
Live from Carnkie, Nr Helston, Cornwall.

Gina
Posts: 1885
Joined: Sat Feb 21, 2009 12:41 pm
Weather Station: Nothing working ATM - making one
Operating System: OS X, Linux Mint, Win7 & XP
Location: Devon UK

Re: Rain Gauge Funnel Multiplier

Postby Gina » Tue Oct 19, 2010 6:43 pm

Mark19 wrote:Thanks alot for that Gina. I never would have worked that out. :lol:
Maths was one of my best subjects at school :D
Gina

Sorry, no banner - weather station out of action. Hoping to be up and running with a new home-made one soon.


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