Author Topic: How to make a Cheap - Rain Gauge Resolution Modification to your OS hardware.  (Read 54456 times)

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Offline sam2004gp

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Re: Cheap - Rain Gauge Resolution Modification
« Reply #25 on: January 03, 2009, 11:26:09 AM »
Well. we just got our first precipitation of the year and the mod works perfectly. It was a slight shower and the station picked it up with the first reading as .01". My database looks like this:

9:00pm            243          0          0         89       45.5      28.91       0.01       45.5       51.0       42.5      29.95       55.6       36.3       0.01       0.01
9:05pm            263          0          0         90       45.3      28.91       0.01       45.3       51.0       42.6      29.95       55.6       36.3       0.01       0.01
9:10pm            221          4          4         91       45.3      28.91       0.01       43.1       51.1       42.9      29.95       55.6       36.3       0.01       0.01
9:15pm            216          0          5         92       45.1      28.91       0.01       45.1       51.1       43.0      29.95       55.6       36.3       0.01       0.01
9:20pm            214          0          0         92       45.1      28.91       0.02       45.1       51.1       43.0      29.95       55.6       36.3       0.02       0.02
9:25pm            245          3          4         93       45.0      28.91       0.03       43.6       51.0       43.1      29.95       55.6       36.3       0.03       0.03
9:30pm            176          0          4         93       44.8      28.91       0.04       44.8       50.9       42.9      29.95       55.6       36.3       0.04       0.04
9:35pm            216          0          4         94       44.8      28.91       0.05       44.8       51.0       43.2      29.95       55.6       36.3       0.05       0.05

The actual total right now is .054 inches. On wundergroud the rain rate went from 0.03 in/hr to 0.13 in/hr and then to 0.17 in/hr at the heaviest point. It seems pretty acurate for the little cell that moved through. I'm happy.
^^^----- =D> \:D/

No rain for me yet, since I installed it.    :sad:
SAM --->>> http://www.mountcrawfordweather.org
OS WMR-968 with a Dedicated PWS Weather Computer running VWS v13.01 p09


Offline sbelmont

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Re: Cheap - Rain Gauge Resolution Modification
« Reply #26 on: January 03, 2009, 11:35:10 AM »
Have you compared it with a CoCoRaHs type gauge? I was shocked at how inaccurate my VP2 is.

No I haven't but it was something that crossed my mind last night. I am that type of person that likes accuracy...

As an update, we've had light showers all night. Except for one brief period at around 12:30 AM where it recorded at 0.02"/hr it has recorded .01" of rain just about every hour this morning. If you look at where I live, Bakersfield, CA, you would know that we do not get much rain. 5.28" is what I saw last calander year. I live in the foothills, so I get a little more precipitation than the valley floor does, but I am sure there were many light showers last year that I did not record any precipitation when I should have with better equipment.

You can check out my data on wunderground as I am not supporting my own web page at this time. My station ID is KCABAKER21.
Steve B
WMR968

Offline sam2004gp

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Re: Cheap - Rain Gauge Resolution Modification
« Reply #27 on: January 03, 2009, 11:43:51 AM »
Just looked at you on wunderground, let me guess, new subdivision?, no house there, just a lot.
SAM --->>> http://www.mountcrawfordweather.org
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Offline sbelmont

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Re: Cheap - Rain Gauge Resolution Modification
« Reply #28 on: January 03, 2009, 12:19:53 PM »
Just looked at you on wunderground, let me guess, new subdivision?, no house there, just a lot.

Golf course has been here since 84. My subdivision was created about 99. I bought the lot in 02 and moved in May of 04. When you look at sat pics you never know what year they are from. I have seen 3 different shots of my current lot. The one on Wunderground is the oldest. My guess is either 01 or 02.
Steve B
WMR968

Offline killwilly

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Re: Cheap - Rain Gauge Resolution Modification
« Reply #29 on: January 04, 2009, 08:54:13 AM »
The satellite pictures on Google Earth are just as ancient, when I take a look at my house it shows a car on my drive which I sold in 2004!

Is it possible that they all use the same shots?
Alan

Offline SlowModem

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Re: Cheap - Rain Gauge Resolution Modification
« Reply #30 on: January 04, 2009, 09:04:33 AM »
I've been at this address for 3 years now.  Yahoo maps show the house, google maps and terraerver do not.
Greg Whitehead
Ten Mile, TN USA


Offline sbelmont

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Re: Cheap - Rain Gauge Resolution Modification
« Reply #31 on: January 04, 2009, 11:32:46 AM »
The satellite pictures on Google Earth are just as ancient, when I take a look at my house it shows a car on my drive which I sold in 2004!

Is it possible that they all use the same shots?

No. I just did a simple test. Map.google.com shows the oldest sat picture of my house, from around 01 or 02. The same one wunderground uses. Maps.yahoo.com uses a newer sat picture. My house is built, but my neighbor's house is just a foundation, so it is from about 05.
Steve B
WMR968

Offline aweatherguy

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Hey, this is creepy! I embarked on an almost identical project -- right down to the automotive funnel!!!

Take a look at it here: http://wmrx00.sourceforge.net

You will need to install the software to get at the user manual. You don't have to use the software but that's the only way to get the manual. Look in the appendix of the user's manual -- there's not as much detailed construction information but this is eerily similar. The only advantage to this idea is that it does not require gluing anything to the original rain gauge.

Also, the WMR100 software there is free and some may find it useful. If you look at the software, feel free to post comments on the Source Forge forum. You can find the forum on the Source Forge project page here: http://sourceforge.net/projects/wmrx00



Offline Total

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I found a 7 3/4 inch or 7.75 funnel - with the new funnel the vws reads .25 MM - sweet

(3.875 (old) / 7.75 (new funnel)) 2  = .25 offset ..  editted ( gain not offset )
« Last Edit: August 11, 2009, 09:11:25 PM by Total »

Offline sam2004gp

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I found a 7 3/4 inch or 7.75 funnel - with the new funnel the vws reads .25 MM - sweet

(3.875 (old) / 7.75 (new funnel)) 2  = .25 offset ..

Gain, not offset
SAM --->>> http://www.mountcrawfordweather.org
OS WMR-968 with a Dedicated PWS Weather Computer running VWS v13.01 p09


Offline DanS

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I found a 7 3/4 inch or 7.75 funnel - with the new funnel the vws reads .25 MM - sweet

(3.875 (old) / 7.75 (new funnel)) 2  = .25 offset ..

Gain, not offset
I get 35.395 gain but what the hey, if it does what you want. \:D/

Offline sam2004gp

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I found a 7 3/4 inch or 7.75 funnel - with the new funnel the vws reads .25 MM - sweet

(3.875 (old) / 7.75 (new funnel)) 2  = .25 offset ..

Gain, not offset
I get 35.395 gain but what the hey, if it does what you want. \:D/

Dan you got to do the math in the correct order.

3.875 /7.75 = 0.5 then square that or the 2 or 0.5 x 0.5  ------ which then equals 0.25
SAM --->>> http://www.mountcrawfordweather.org
OS WMR-968 with a Dedicated PWS Weather Computer running VWS v13.01 p09


Offline DanS

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I found a 7 3/4 inch or 7.75 funnel - with the new funnel the vws reads .25 MM - sweet

(3.875 (old) / 7.75 (new funnel)) 2  = .25 offset ..

Gain, not offset
I get 35.395 gain but what the hey, if it does what you want. \:D/

Dan you got to do the math in the correct order.

3.875 /7.75 = 0.5 then square that or the 2 or 0.5 x 0.5  ------ which then equals 0.25
It's getting late here and my brain cell is dwindling. I thought you got the area of each with squaring the radius x pi. Like for 3.875's radius 1.9375 x 1.9375 =  3.7539 * 3.143 = 11.798 do the same for the 7.75 and subtract to get the difference between the two? no?.
« Last Edit: July 14, 2009, 11:17:50 AM by DanS »

Offline sam2004gp

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Well we are not looking for the total area of collection, we are looking for the difference in the Gain from the original un-modified OS gauge to the New size circumference.  The current actual area of collection makes no difference, just the difference of the two area collection numbers.  So rather than doing a large amount of math on all of that it can be brought down to:

Quote
Now I will have the following Measurements, in regards to my NEW rainfall collection funnel for the OS-WMR968 station.

d=3 7/8 Inches (Original collection funnel size on the unmodified rain gauge.)
D=7 3/8 inches (The size of the NEW rain collection funnel)

So Again using the formulas posted later on in this thread and a little logic we get...
New Gain = (d / D)2    
...or me....
.2760 = (3.875 / 7.375)2

So I will enter into the VWS calibration window a gain of .2760
.............

To get the new accuracy of resolution factor we do this math.
(Old Accuracy x New Gain)  or again in my case...
(.04 x .2760) = .01104

Which translates to that after every internal bucket/lever trip that occurs in my rain gauge.  I will record .011 inches of rain., instead of the original .04 inches of rain that occurred with the "Old" version of the rain gauge.

OR

Quote
Here are the formulas for anyone who is interested. It's actually pretty straighforward and can be determined without using areas and without Pi.


Let d denote the inside diameter of the manufacturer's funnel (measured at the top).


Let Coarse denote the resolution of the manufacturer's rain gauge (0.04 inches for the OS, for example).


Let Fine denote the finer resolution you'd like from your modified collector (like 0.01 inches).


Then you need a funnel whose inside diameter D (measured at the top) is

       D  =  d * sqrt(Coarse / Fine)


Then set a gain in your station so that it knows each tip of the bucket now represents Fine inches of rain:

      Gain  =   Fine / Coarse.        This is the same as ( d / D )2.


Example:  Suppose your rain gauge has a resolution of 0.04 inches. Suppose the manufacturer's funnel measures 3.875 inches across the top (diameter). Suppose you want to modify the funnel to have a finer resolution of 0.01 inches. So

      d  =  3.875,    Coarse  =  0.04,    Fine  =  0.01,

and you need a new funnel whose inside diameter (across the top) is

      D  =  d * sqrt(Coarse / Fine)   =   3.875 * sqrt(0.04/0.01)  =  7.75 inches,

and you need to set a gain of

     Gain  =   Fine/Coarse  =  (0.01/0.04)  =  0.25

on your station.

Regards,

Kevin...
« Last Edit: July 14, 2009, 11:30:20 AM by sam2004gp »
SAM --->>> http://www.mountcrawfordweather.org
OS WMR-968 with a Dedicated PWS Weather Computer running VWS v13.01 p09


Offline DanS

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Gotcha..they say as you age your memory is the second thing to go. I'll bet a Bahama Mama would put the ol' attic back in order. #-o
Gotta go hit the sack, the mrs. is calling. later ...

Offline sam2004gp

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"...Knock out those dust bunnies."  ;)
SAM --->>> http://www.mountcrawfordweather.org
OS WMR-968 with a Dedicated PWS Weather Computer running VWS v13.01 p09


Offline Downlinerz2

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FYI:   I found a source for good funnels for this mod.  They are already white, they have vertical wall at the top, and they have a larger screen than usual. 

                 http://homebrewmart.com
   
                                  Mark

Offline sam2004gp

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FYI:   I found a source for good funnels for this mod.  They are already white, they have vertical wall at the top, and they have a larger screen than usual. 

                 http://homebrewmart.com
   
                                  Mark

I can't seem to track them down exactly, do you have a direct link?
SAM --->>> http://www.mountcrawfordweather.org
OS WMR-968 with a Dedicated PWS Weather Computer running VWS v13.01 p09


Offline Downlinerz2

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  Sam,
    Sorry.  Here is the most direct link I could get:

   1)   http://homebrew-supplies.homebrewmart.com/shared/storefront/default.asp?CS=hbm&storetype=BtoC&count1=537822902&count2=454963326&categoryID=30&target=products.asp
   2)On this page click on "Equipment"
   3) Go to page 2 of 8
   4) 8" funnel is at the bottom of the page

    (I could not get a link straight to the funnel page.  Sorry ](*,)

Offline Total

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I found a 7 3/4 inch or 7.75 funnel - with the new funnel the vws reads .25 MM - sweet

(3.875 (old) / 7.75 (new funnel)) 2  = .25 offset ..

Gain, not offset
I get 35.395 gain but what the hey, if it does what you want. \:D/

Dan you got to do the math in the correct order.

3.875 /7.75 = 0.5 then square that or the 2 or 0.5 x 0.5  ------ which then equals 0.25

One final question . For MM is the gain still .25 ?? for my above #'s ..

Offline Downlinerz2

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FYI:   I found a source for good funnels for this mod.  They are already white, they have vertical wall at the top, and they have a larger screen than usual. 

                 http://homebrewmart.com
   
                                  Mark

I can't seem to track them down exactly, do you have a direct link?
     Sam,
         Have you been able to find the funnels? 

Offline sam2004gp

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I found a 7 3/4 inch or 7.75 funnel - with the new funnel the vws reads .25 MM - sweet

(3.875 (old) / 7.75 (new funnel)) 2  = .25 offset ..

Gain, not offset
I get 35.395 gain but what the hey, if it does what you want. \:D/

Dan you got to do the math in the correct order.

3.875 /7.75 = 0.5 then square that or the 2 or 0.5 x 0.5  ------ which then equals 0.25

One final question . For MM is the gain still .25 ?? for my above #'s ..

Yes your gain of .25 is correct.
SAM --->>> http://www.mountcrawfordweather.org
OS WMR-968 with a Dedicated PWS Weather Computer running VWS v13.01 p09


Offline sam2004gp

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     Sam,
         Have you been able to find the funnels? 

Yes  I saw them, thanks. :-)
SAM --->>> http://www.mountcrawfordweather.org
OS WMR-968 with a Dedicated PWS Weather Computer running VWS v13.01 p09


Offline Total

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I changed my funnel AGAIN .. SIGH ... I noticed with the angle of the bottom of the old funnel , water drops would hang there and not travel into the rain gauge .. Much better now ..  The new funnel is exactly 7.75 inches .. 

We had a little shower come thru here this morning . after I checked and no more Water hanger anymore ..

 
« Last Edit: August 16, 2009, 01:24:43 PM by Total »

Offline Strgazr27

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Re: How to make a Cheap - Rain Gauge Resolution Modification to your OS hardware.
« Reply #49 on: September 09, 2009, 01:09:53 PM »
Absolutely the best mod for the OS unit. I'm hoping to add heat to mine this weekend. Winter isn't that far away  ](*,)
Bobby M.
Davis VP2 6152 w Daylight FARS - Logitech C525 and C310
WD - WDLive - GRLevel3 - Image Salsa - VVP - Startwatch

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