Author Topic: RG11 as a rain rate/intensity detector  (Read 3557 times)

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Offline SLOweather

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RG11 as a rain rate/intensity detector
« on: October 30, 2016, 06:57:53 PM »
I have 2 of my RG11s connected to an industrial controller, one as a drop counter, one as 0.0001" tipping bucket.

During a rain, I took 15 sets of readings, once a minute, and reduced the data.



Especially on the drop counter, you can see the waves of rain pass through.

Now to automate the data logging and add a Davis gauge before it rains again.

Offline kmahler

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Re: RG11 as a rain rate/intensity detector
« Reply #1 on: October 30, 2016, 08:35:29 PM »
SLOweather,

Have you tried working with any of the Ardunio products to set up a data collector? If you have even a basic understanding of programming they are pretty easy to program to do most anything you want. A program in the IDE is called a "sketch". There are some pretty simple sample sketches out there for free to read from the RG-11. That's what I'm doing my experimenting with.

Kevin
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Offline SLOweather

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Re: RG11 as a rain rate/intensity detector
« Reply #2 on: November 02, 2016, 12:12:00 AM »
Hi Kevin,

Way back in '97, I did a lot with Basic Stamp 2s. I even had an article published in Circuit Cellar Ink regarding a project.

Alas, almost 20 years later, I am currently wrapped up in elder care, and my time is limited. I just don't have the room in the daily schedule right now to get involved in the Arduino/RPi craze.

OTOH, I have 20 years as a utility controls tech, and, post retirement, I am responsible for maintaining and upgrading the controls system for our small mutual water company. And, because of that, I have a lot of Ebayed surplus industrial controllers laying around. So, I play with those. I know the programming, all of the interfacing and display, such as it is, it taken care of for me, and extending my programming abilities by playing with weather instruments makes me a better programmer for my water company.

Having said that, you might be interested in something rain related I cooked up almost 10 years ago.

Take a Lexan window pane and mount it on top of a wooden frame. Glue a piezo transducer to the middle of the underside. Jack the transducer into a mike jack on a PC. Put it out in the rain and run a strip chart program.

Watch the waves of rain roll through...



More here:

http://www.weather-watch.com/smf/index.php/topic,21358.0.html

and here:

http://www.wxforum.net/index.php?topic=1428.msg10392#msg10392

Somewhere I posted links to some wav files I recorded of rainfall on the transducer. I'll see if I can find them.

Offline SLOweather

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Re: RG11 as a rain rate/intensity detector
« Reply #3 on: November 02, 2016, 12:21:13 AM »
Hijacking my own RG11 thread... :)

A picture of the piezo rain transducer:



Heavy rain recording
http://www.sloweather.com/blog/2009/090124hevrain4.wav  (1:10 minutes, 12.1 MB)

Light rain recording
www.sloweather.com/blog/2009/090124lightrain.wav (1:00 minute, 10.3 MB)

Offline Old Tele man

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Re: RG11 as a rain rate/intensity detector
« Reply #4 on: November 02, 2016, 10:03:49 AM »
Rain *amount* is measured in VOLUME...cubic inches per square-inch per unit time...however, each falling rain drop has multiple characteristics: (1) physical size/volume, (2) velocity, and (3) impact rate. Also, at the cross-over from water into ice, even #1 physical size/volume changes!
SYS: Davis VP2/WL-IP & Envoy8X/WL-USB
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Offline SLOweather

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Re: RG11 as a rain rate/intensity detector
« Reply #5 on: November 02, 2016, 11:37:17 AM »
Exactly... That's why one of the parts of this experiment is to divide the drop count by the rain gauge reading (currently 0.0001" TB emulation), to see how many drops make up each tip.

Here's a chart of drops per tenthousandth from that sample data.



Keep in mind that the base data was recorded every 60 seconds so this is 15 minutes of samples

I talked with Hydreon a while back and they either didn't know or wouldn't tell me what the effective aperture or effective surface area of the sensor is, so I could use that to calculate drop volume. So, I'll have to measure or calculate or estimate it.

Due to the admitted inaccuracies of the units, I'm not really sure if the outcome will be useful or not. I suppose I will have to try to compare results with perceived drop size.

And, not knowing the underlying algorithms Hydreon uses, I wonder about any "self-referential" error that might creep in. I believe it has some finite integration time, because sometimes on the TB unit, I would get 2 quick clicks in a row, like it was trying to catch up. 

Rain *amount* is measured in VOLUME...cubic inches per square-inch per unit time...however, each falling rain drop has multiple characteristics: (1) physical size/volume, (2) velocity, and (3) impact rate. Also, at the cross-over from water into ice, even #1 physical size/volume changes!

Offline SLOweather

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Re: RG11 as a rain rate/intensity detector
« Reply #6 on: November 21, 2016, 01:19:50 PM »
Over the last few days, I finished setting up my rain lab, installing the cabling, and getting the logging programming written just in time for some rain yesterday.

This is from 10:21 until about 19:00 yesterday, Sunday. I logged the counters from the RG11 in drop counting mode and ten thousandths TB mode. The I opened the CSV file in LibreOffice Calc and subtracted subsequent readings from the previous one to get drops or ten thousandths per minute and graphed it.



It shows pretty clearly the waves of rain going through.

Offline Old Tele man

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Re: RG11 as a rain rate/intensity detector
« Reply #7 on: November 21, 2016, 02:44:32 PM »
What does the preliminary mathematical correlation analysis look like? R2 > 0.90?
SYS: Davis VP2/WL-IP & Envoy8X/WL-USB
CWOP: DW6988 - 2 miles NNE of Cortaro, AZ
WU - KAZTUCSO202, Countryside

Offline SLOweather

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Re: RG11 as a rain rate/intensity detector
« Reply #8 on: November 23, 2016, 04:49:03 PM »
What does the preliminary mathematical correlation analysis look like? R2 > 0.90?

Correlation of what to what?

Actually, I'd like to compare it to a tipper, but right now I have a problem.

The RG11 data is "synchronous". That is, the numbers come in so fast that I record the totals once a minute.

However, the 0.01" tippers are "asynchronous". They are comparatively so slow that I record the seconds between individual tips, and, last rain, didn't record the time stamps for each tip.

So, I need to time stamp that data, or otherwise figure out how to compare the 2 data sets.

Offline Old Tele man

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Re: RG11 as a rain rate/intensity detector
« Reply #9 on: November 23, 2016, 06:17:41 PM »
As a "first-cut" analysis: what's ORANGE line vs. BLUE line (and vice-versa) look like? Somewhat linear or just a 'cloud' of dots vs. dots?
SYS: Davis VP2/WL-IP & Envoy8X/WL-USB
CWOP: DW6988 - 2 miles NNE of Cortaro, AZ
WU - KAZTUCSO202, Countryside

Offline SLOweather

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Re: RG11 as a rain rate/intensity detector
« Reply #10 on: November 24, 2016, 10:07:08 AM »
It won't be linear. The blue line is "drops per minute" as counted by one RG11. The orange line is "emulated ten-thousandths of an inch tipping bucket tips per minute" as measured by a second RG11 about a foot away from the first at the same elevation.

The first RG11 is supposed to count individual drops, no matter the size. The second is supposed to integrate drops, measuring or estimating their size, into ten-thousandths of an inch.

Dividing the first by the second should give a number of drops per ten-thousandth of an inch,and thereby some indication of the drop size. (more drops per 0.001" = smaller drops...)

I cooked up a graph of that, and then realized that it's not quite accurate, because some record have drops, but no 0.001" so I have to sum successive minute's drops at those times.

Offline SLOweather

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Re: RG11 as a rain rate/intensity detector
« Reply #11 on: November 25, 2016, 06:21:49 PM »
OK. I crunched the data a little more. This first graph is of rain drops per ten-thousandth of an inch of rain over time. Per the calculation, the taller the line, the more rain drops it took to integrate 1 ten-thousandth of an inch of rain. Therefore, the taller the line, the smaller the drops.



This is the same data, only sorted fewer drops to more drops per ten-thousandth, or larger to smaller drops.



The average is 7.3 drops/0.0001", the median is 5.6 drops, minimum is 1, maximum is 132.
« Last Edit: November 25, 2016, 06:26:38 PM by SLOweather »

Offline SLOweather

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Re: RG11 as a rain rate/intensity detector
« Reply #12 on: November 25, 2016, 06:31:01 PM »
Now if I can figure out a reasonably accurate area for the sensor, I could estimate drop volume. It's complicated by the domed shape of the sensing area.

Also, if I determine that, I don't know whether to use the area of the dome, or the area of its circular cross section.


Offline SLOweather

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Re: RG11 as a rain rate/intensity detector
« Reply #13 on: November 28, 2016, 01:30:47 AM »
I decided to make some assumptions re: the RG11. I decided that the effective sensor diameter was 45 mm at the top of the LED cones, and that the effective sensing area was a circle of that diameter.

After applying some mind numbing math (or, as Mark Watney would say, "Scienceing the sh!t out of it.") and correcting an error I made in the volume of a sphere, I actually came up with a reasonable number.

I truncated the median value to 5 drops of rain per 0.0001". It comes out to...  drops of 2.48 mm diameter.

From http://www.shorstmeyer.com/wxfaqs/float/rdtable.html

A large drop in a Moderate Stratiform Rain (.25'' per hour) has a diameter of... 2.6 mm. (Small drop diameter of 1.0 mm.)

Now to reduce all those calcs to a single equation. Then I can use that table to quantify rain on the fly.
« Last Edit: November 28, 2016, 09:21:54 AM by SLOweather »

Offline SLOweather

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Re: RG11 as a rain rate/intensity detector
« Reply #14 on: December 06, 2016, 01:52:57 PM »
Well...

First of all, I reviewed my previous work and realized that I had misplaced a decimal point. So, instead of a diameter of 2.48mm the 5 drops/0.0001" drop size is 1.15 mm diameter, which is a better number per the site I listed above.

Herewith, a graph of that rain event, this time by drop diameter in mm...



Offline Old Tele man

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Re: RG11 as a rain rate/intensity detector
« Reply #15 on: December 06, 2016, 02:28:52 PM »
Does the integration of all those areas add-up to the rain total that you got by alternate measurement?
SYS: Davis VP2/WL-IP & Envoy8X/WL-USB
CWOP: DW6988 - 2 miles NNE of Cortaro, AZ
WU - KAZTUCSO202, Countryside

Offline SLOweather

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Re: RG11 as a rain rate/intensity detector
« Reply #16 on: December 06, 2016, 06:26:00 PM »
Thanks to graculus and bushman for the pointers in another thread.

Here's a histogram of the drop diameter distribution for the rain event data I've been working with.

Excel is so cool. (Although I also use LibreOffice Calc, too.  I like its graphing function better.)


Offline SLOweather

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Re: RG11 as a rain rate/intensity detector
« Reply #17 on: December 06, 2016, 06:37:57 PM »
Here's the same data by .01 mm increments...


Offline Bushman

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Re: RG11 as a rain rate/intensity detector
« Reply #18 on: December 06, 2016, 06:47:12 PM »
Neat!  Basically a bell curve - normal distribution.  Now you need to correlate the drop size with rate/intensity etc.   :)

Offline WheatonRon

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Re: RG11 as a rain rate/intensity detector
« Reply #19 on: December 06, 2016, 08:45:59 PM »
Here's the same data by .01 mm increments...



Excel is a complex program that requires a bit of trial and error to use, but at the end of the day, it is one of the most powerful and useful software applications a person will ever use in his or her lifetime! Thanks in part to the fore runner of this program, Visicalc! Any body that remembers that program has to be at least 50 and possibly 60 years old! Lotus 1-2-3 also contributed to the functionality in Excel.
« Last Edit: December 06, 2016, 09:27:46 PM by WheatonRon »
Davis VP2 with Daytime FARS, SHT31 (2 complete systems-1 for uploading to the internet, the other system for test and play); Rainwise 111; CWOP--CW5020; WU--KILWHEAT17; CoCoRaHS--IL-DP-132

Offline Bushman

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Re: RG11 as a rain rate/intensity detector
« Reply #20 on: December 06, 2016, 09:25:35 PM »
Visicalc was late to the game.  Remember Multiplan?  :)

Offline graculus

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Re: RG11 as a rain rate/intensity detector
« Reply #21 on: December 06, 2016, 09:43:36 PM »
Nice histogram SLO  :-)

Quattro Pro and the "look 'n feel" lawsuit anyone?

Excel was on the Mac first in 1985, it was amazing compared to Lotus 1-2-3 and Lotus really never caught up  :-(

Offline WheatonRon

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Re: RG11 as a rain rate/intensity detector
« Reply #22 on: December 06, 2016, 09:52:32 PM »
Visicalc was late to the game.  Remember Multiplan?  :)

Actually, I don't remember Multiplan. Who made it?
Davis VP2 with Daytime FARS, SHT31 (2 complete systems-1 for uploading to the internet, the other system for test and play); Rainwise 111; CWOP--CW5020; WU--KILWHEAT17; CoCoRaHS--IL-DP-132

Offline PaulMy

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Re: RG11 as a rain rate/intensity detector
« Reply #23 on: December 06, 2016, 11:16:43 PM »

Quote
Actually, I don't remember Multiplan. Who made it?


HesWare Microsoft Multiplan!  for the Commodore 64
HesWare Human Engineered Software
Licensed from Microsoft Corporation


Paul


Offline SLOweather

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Re: RG11 as a rain rate/intensity detector
« Reply #24 on: December 07, 2016, 10:06:33 AM »
Visicalc was late to the game.  Remember Multiplan?  :)

Dunno about that. Maybe Visicalc was late to the PC.  Coincidentally, a few days ago I reread Dan Bricklin's history of Visicalc.
http://www.bricklin.com/history/saiidea.htm

It's quite interesting. Visicalc was developed for the Apple ][, and I believe is the second computer program I ever bought. (I got my first Apple ][ + in January '82. The first program I purchased as a database program called Data Reporter. We used it to manage our wedding.)

As early as '79, Visicalc was seen as the "killer app" that legitimized the personal computer industry. Ben Rosen from Morgan Stanley said:

Quote
"So who knows? Visicalc could some day become the software tail that wags (and sells) the personal computer dog."

From the Multiplan Wikipedia page:

Quote
Multiplan was an early spreadsheet program developed by Microsoft. Known initially by the code name "EP" (for "Electronic Paper"), it was introduced in 1982 as a competitor for VisiCalc.

Hmmm, I may still have my original Visicalc disk around here somewhere...

 

anything