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Weather Station Hardware => Davis Instruments Weather Stations => Topic started by: Intheswamp on May 29, 2018, 11:58:33 AM

Title: Davis VP2 Rain Gauge
Post by: Intheswamp on May 29, 2018, 11:58:33 AM
For several years I've been running my VP2 station with the understanding that the rain gauge "may" record low during times of heavy rain.  A good friend about four miles away from me has many times reported to me more rain than what my Davis unit has recorded.  He has a basic 1" diameter gauge.  I figured there was the distance between our locations, his location in regards to trees, buildings, etc., (mine ISS location is fantastic...right?  :roll: ), the "if it rains hard it will record low" idiom, etc., that was causing sometimes an inch or more difference in readings.  Naturally, if we were talking about scattered showers the differences are understandable, but when talking about a set-in, widespread rain system it seems that 4 miles wouldn't make too big of a difference...the differences in our gauges did make me wonder.

Sub-tropical storm Alberto passed through here last night.  For the same time period of prior to Alberto's arrival until this morning the readings were: 

Davis VP2  =  2.59"
CoCoRaHS =  3.60"

The two measuring instruments are roughly 60' apart from each other.  The CoCoRaHS gauge has a large pine tree probably 30' to the NW of it.  I know, to do a better comparison the two gauges should be basically mounted side-by-side.  But...a whole inch of difference?  Seems like a bit much to me.  I've never looked into it, but can the VP2's rain gauge be "calibrated"?

Feedback definitely welcome!!!
Ed
Title: Re: Davis VP2 Rain Gauge
Post by: johnd on May 29, 2018, 12:22:34 PM
Feedback definitely welcome!!!

OK: What was the range of rainfall rates that were logged during the storm?
Title: Re: Davis VP2 Rain Gauge
Post by: Intheswamp on May 29, 2018, 12:48:40 PM
At 60-feet separation, "micro-climate" differences definitely have to be considered.

I can recall, on Guam, refueling one wing-tip tank on EC-12K and getting "douched" but the sailor refueling the other wing-tip tank, 120-feet away, not getting a drop.

My family's business (father started in 1946) sat on a corner downtown, basically center of town.  I've looked out the front (west) windows and it be pouring down rain and out the side windows to the south not a drop be falling.  Also, the one end of a bridge being dry, the other end wet, etc.,.  It just seems that with that small of a distance and the storm conditions that we had the readings would have been closer to each other.  I will say that the other day I compared a smaller rainfall amount and the two gauges were much closer in their measures.

It could have been a quirk, it's just hard for me to understand an inch difference. But, it's hard for me to understand lots of things...just ask my wife.  :lol:
Title: Re: Davis VP2 Rain Gauge
Post by: Intheswamp on May 29, 2018, 01:05:32 PM
Feedback definitely welcome!!!

OK: What was the range of rainfall rates that were logged during the storm?
Here's a screen capture from my graph page.   The best that I can tell, either side of midnight was when the center of Alberto was passing over us.  I was thinking that the rainfall rate should be higher than shown, but there was a lot of slow, steady rain involved. :-k  At that time, though, I was snoozing.  :grin: 
(https://farm2.staticflickr.com/1723/40622890650_9ff042024e_b.jpg)
Title: Re: Davis VP2 Rain Gauge
Post by: Intheswamp on May 29, 2018, 01:07:18 PM
At 60-feet separation, "micro-climate" differences definitely have to be considered.

I can recall, on Guam, refueling one wing-tip tank on EC-12K and getting "douched" but the sailor refueling the other wing-tip tank, 120-feet away, not getting a drop.

My family's business (father started in 1946) sat on a corner downtown, basically center of town.  I've looked out the front (west) windows and it be pouring down rain and out the side windows to the south not a drop be falling.  Also, the one end of a bridge being dry, the other end wet, etc.,.  It just seems that with that small of a distance and the storm conditions that we had the readings would have been closer to each other.  I will say that the other day I compared a smaller rainfall amount and the two gauges were much closer in their measures.

It could have been a quirk, it's just hard for me to understand an inch difference. But, it's hard for me to understand lots of things...just ask my wife.  :lol:
I see your wife studied the same book(s) as mine (wink,wink).
I don't think they have to study...it's in their DNA!!!  ;)
Title: Re: Davis VP2 Rain Gauge
Post by: WheatonRon on May 29, 2018, 01:58:20 PM
Calibration instructions attached, from the Davis “rain collector with mountable base” user manual (the same one used in the VP2). Quite frankly, I have given up on the accuracy of the rain tool in the VP2. After trying on 4 separate VP2 rain bases using both the old collector and the new “aero cone” collector design, I gave up. I tried calibration and that didn’t help. My Rainwise 111 always matches my CoCo gauge in all material respects, my VP2s, rarely. I should connect my Rainwise to my VP2 ISS, and move on with life. Unfortunately, it would likely be an ugly setup in my back yard, so my wife would likely veto the concept. See next post from Randy at ValentineWeather on how to hook up the Rainwise.
Title: Re: Davis VP2 Rain Gauge
Post by: ValentineWeather on May 29, 2018, 02:16:09 PM
The rain rates are not bad at all shows just how inaccurate they can be.

I've purchased multiple stand alone Davis rain gauges thinking I could get one to work but it was always the same. (Before they came out with the cone) My conclusion something was inherently wrong with gauge design itself and I think Davis coming out with the cone proves my findings of design flaw.

30% error was my typical experience with the Davis tipping bucket. Sometimes it may be much closer 0-5% but next time 30 even 50% off.
It was like opening a box of chocolates you never knew what you were going to get. I finally discovered the Rainwise 111.   

For about $80 you can install and Rainwise 111 8" diameter tipping bucket gauge which will follow the manual Cocorahs closely. It also has adjustment screws but tend to come close right out of box if mounted on level flat surface.
You can use the existing Davis plug and just splice into it.....green/yellow one side and red the other.
 [ You are not allowed to view attachments ]
Title: Re: Davis VP2 Rain Gauge
Post by: Intheswamp on May 29, 2018, 03:00:26 PM
All of you do realize ya'll *are* terrible enablers, don't you!!!???  :grin:

Rainwise, eh?  :-k

So, we take the terminals of the RW gauge that are intended to go to the wired "inside counter" and connect them to the rain connection port of the Davis ISS?  Rather than the signal going to the counter it goes to the ISS and the ISS interprets and sends to the Davis console with no problem?  That's it? :?:
Title: Re: Davis VP2 Rain Gauge
Post by: CW2274 on May 29, 2018, 03:47:22 PM
All of you do realize ya'll *are* terrible enablers, don't you!!!???  :grin:

Rainwise, eh?  :-k

So, we take the terminals of the RW gauge that are intended to go to the wired "inside counter" and connect them to the rain connection port of the Davis ISS?  Rather than the signal going to the counter it goes to the ISS and the ISS interprets and sends to the Davis console with no problem?  That's it? :?:
Yep. Works exactly the same. Randy talked me into doing this (a/c fan too) and never looked back. =D>
Title: Re: Davis VP2 Rain Gauge
Post by: ValentineWeather on May 29, 2018, 03:48:41 PM
All of you do realize ya'll *are* terrible enablers, don't you!!!???  :grin:

Rainwise, eh?  :-k

So, we take the terminals of the RW gauge that are intended to go to the wired "inside counter" and connect them to the rain connection port of the Davis ISS?  Rather than the signal going to the counter it goes to the ISS and the ISS interprets and sends to the Davis console with no problem?  That's it? :?:

Yes you will just slice into counter wire (2 wires) . Leave a couple feet of wire connected to counter plug you can still use counter to calibrate without disrupting the station rainfall later if needed. Very simple to do.

If you do this Rainwise is usually cheaper than other places for gauge. https://www.rainwise.com/products/detail.php?ID=6697
Title: Re: Davis VP2 Rain Gauge
Post by: Intheswamp on May 29, 2018, 03:55:45 PM
You know, if I hadn't ever put up that Cocorahs gauge I wound't now this...or be worried about it.  Ignorance is bliss...sometimes. #-o

I'm part caveman, so I think I can do this....sounds like a simple job.

Ok, is the shelf necessary or is a d-i-y option doable?

Title: Re: Davis VP2 Rain Gauge
Post by: CW2274 on May 29, 2018, 04:00:36 PM
Ok, is the shelf necessary or is a d-i-y option doable?
:?:
Title: Re: Davis VP2 Rain Gauge
Post by: Intheswamp on May 29, 2018, 04:31:55 PM
Apparently it's not a requirement. :)

I found this on ambientweather.com...  (https://sep.yimg.com/ca/I/yhst-37697109791737_2270_77985795)
Title: Re: Davis VP2 Rain Gauge
Post by: CW2274 on May 29, 2018, 04:41:04 PM
No. However, if you do get the RW, make it as level as you can get and make it sturdy enough that strong, gusty wind will not move it. For example, I have mine screwed into the top of my cider block wall, it ain't movin' for nuthin'.
Title: Re: Davis VP2 Rain Gauge
Post by: ValentineWeather on May 29, 2018, 04:44:38 PM
Nice shelf, I'm using a 4x4 post and plastic cutting board... :lol:
Title: Re: Davis VP2 Rain Gauge
Post by: Intheswamp on May 29, 2018, 04:51:05 PM
If I get it I'd like to mount it on the backside of the post that I have the Davis unit on.  I have the top of the post sawn off to slope away from the Davis bucket...I wonder if I just mounted the RW where the top of the bucket was a few inches above the top of the post if that would keep the rain splatter from the post away from it...???   Probably just need to bite the bullet and re-saw it to slope the opposite direction.

Has anybody fitted bird spikes to the RW bucket?  That is one thing that I have *really* enjoyed with the new style Davis bucket...I've had zero problem with debris/avian-gifts.

Hmm, VW your cutting board shelf sounds interesting.  If I cut the 4x4 post level I could simply screw the cutting board down to it.  Does the RW bucket need an opening below it so the water can pass through easily??...in other words, not a solid surface below it?
Title: Re: Davis VP2 Rain Gauge
Post by: ValentineWeather on May 29, 2018, 04:53:10 PM
Tipping buckets
Title: Re: Davis VP2 Rain Gauge
Post by: Mattk on May 29, 2018, 04:55:35 PM
Current VP2 rain gauges are no where near the consistency of earlier models like used on the WMII but they can be calibrated there is no question about that but being a tipper like any tipper different rate rates will provide different rain fall.   
Title: Re: Davis VP2 Rain Gauge
Post by: ValentineWeather on May 29, 2018, 05:09:58 PM


Hmm, VW your cutting board shelf sounds interesting.  If I cut the 4x4 post level I could simply screw the cutting board down to it.  Does the RW bucket need an opening below it so the water can pass through easily??...in other words, not a solid surface below it?

I'm actually using a green cedar fence post ranchers use around here. You can always make a drain hole if needed on platform. I'm up enough for leveling on one side so have no issues. These have no bubble gauge so just level the direction tippers sit most important with 3' level across top. 
Title: Re: Davis VP2 Rain Gauge
Post by: CW2274 on May 29, 2018, 05:36:50 PM
Does the RW bucket need an opening below it so the water can pass through easily??...in other words, not a solid surface below it?
You can always make a drain hole if needed on platform.
Not necessary. There's ample room underneath for the rain to easily pass through, solid surface or not.
Title: Re: Davis VP2 Rain Gauge
Post by: ValentineWeather on May 29, 2018, 05:45:18 PM
Does the RW bucket need an opening below it so the water can pass through easily??...in other words, not a solid surface below it?
You can always make a drain hole if needed on platform.
Not necessary. There's ample room underneath for the rain to easily pass through, solid surface or not.
I wasn't positive because mine sits up anyway.
Title: Re: Davis VP2 Rain Gauge
Post by: Intheswamp on May 29, 2018, 05:49:43 PM


Hmm, VW your cutting board shelf sounds interesting.  If I cut the 4x4 post level I could simply screw the cutting board down to it.  Does the RW bucket need an opening below it so the water can pass through easily??...in other words, not a solid surface below it?

That looks like plenty of room...if it rains heavy enough to clog that up I'll be looking around for an ark to run jump into!!!!

I'm actually using a green cedar fence post ranchers use around here. You can always make a drain hole if needed on platform. I'm up enough for leveling on one side so have no issues. These have no bubble gauge so just level the direction tippers sit most important with 3' level across top.
Title: Re: Davis VP2 Rain Gauge
Post by: SLOweather on May 29, 2018, 07:45:34 PM
All of you do realize ya'll *are* terrible enablers, don't you!!!???  :grin:

Oh, yeah. We like spending other people's money. Thor knows, these guys have spent enough of mine...
Title: Re: Davis VP2 Rain Gauge
Post by: WxLover16 on May 29, 2018, 09:25:53 PM
To get straight to the point here, I don't even use my VP2 for my "official" rainfall measurements. Even in light rain, it under-reports (albeit very little-but still). All I use it for is a tool to see how hard it's raining; aka the rain rate. I rarely even pay attention to how much it reports. My cocorahs guage is what I use. I just don't understand why there are always posts like these because an electronic (spoon tip) rain guage will never be as accurate as a manual. It might be interesting to compare, but in the end the manual will not under-report.
Title: Re: Davis VP2 Rain Gauge
Post by: Intheswamp on May 29, 2018, 09:42:43 PM
Well, yeah...the manual will always be more accurate.

Well, yeah...I'll always be a bit lazy.  Just get me in the ballpark and gimmie a beer...  :lol:

Seriously, though, I can't (don't know how) to automatically pull in manual readings into my website.  So getting as close as I can to an automated reading is very desirable for me. 

The above paragraph sounds rather confusing even to me, and I wrote it.

Title: Re: Davis VP2 Rain Gauge
Post by: WxLover16 on May 29, 2018, 09:50:13 PM
Well, yeah...the manual will always be more accurate.

Well, yeah...I'll always be a bit lazy.  Just get me in the ballpark and gimmie a beer...  :lol:

Seriously, though, I can't (don't know how) to automatically pull in manual readings into my website.  So getting as close as I can to an automated reading is very desirable for me. 

The above paragraph sounds rather confusing even to me, and I wrote it.

Off-topic here but just wondering, I see your location is basically due south of Montgomery. Did you get into the eye-wall of Alberto?
Title: Re: Davis VP2 Rain Gauge
Post by: CW2274 on May 29, 2018, 10:00:46 PM
but in the end the manual will not under-report.
Not necessarily, splash out has been documented by Valentine WX (Randy) when using the Coco in downpours with it's "smallish" depth of cone.
Title: Re: Davis VP2 Rain Gauge
Post by: Intheswamp on May 29, 2018, 10:28:16 PM
but in the end the manual will not under-report.
Not necessarily, splash out has been documented by Valentine WX (Randy) when using the Coco in downpours with it's "smallish" depth of cone.
You know, I was wondering about that.  It does seem rather shallow, but still seems to do better than the Davis.  :???:
Title: Re: Davis VP2 Rain Gauge
Post by: CW2274 on May 29, 2018, 10:31:01 PM
but in the end the manual will not under-report.
Not necessarily, splash out has been documented by Valentine WX (Randy) when using the Coco in downpours with it's "smallish" depth of cone.
You know, I was wondering about that.  It does seem rather shallow, but still seems to do better than the Davis.  :???:
Ain't nothin' perfect...
Title: Re: Davis VP2 Rain Gauge
Post by: ValentineWeather on May 30, 2018, 12:12:06 AM
Ain't nothin' perfect...

Not because of lack of effort. :idea:  I've modified a couple tops to prevent splash out and even catch hail now.
Title: Re: Davis VP2 Rain Gauge
Post by: CW2274 on May 30, 2018, 12:55:09 AM
Ain't nothin' perfect...

Not because of lack of effort. :idea:  I've modified a couple tops to prevent splash out and even catch hail now.
For sure. Although not as convenient, one can always just remove the funnel and tube and take the catch and pour it into the tube for measurement later. Problem is, it's later. I like knowing now, at a glance, through the dry side of my window.
Title: Re: Davis VP2 Rain Gauge
Post by: Intheswamp on May 30, 2018, 10:13:00 PM
Well, yeah...the manual will always be more accurate.

Well, yeah...I'll always be a bit lazy.  Just get me in the ballpark and gimmie a beer...  :lol:

Seriously, though, I can't (don't know how) to automatically pull in manual readings into my website.  So getting as close as I can to an automated reading is very desirable for me. 

The above paragraph sounds rather confusing even to me, and I wrote it.

Off-topic here but just wondering, I see your location is basically due south of Montgomery. Did you get into the eye-wall of Alberto?
Yeah, it pretty much wiped it's feet on our front door mat.  Not a big event, though.  A lot of rain, some wind, but nothing as bad as some thunderstorms that come through from time to time...just longer period of rain and wind.  It was very unlike Opal that pretty well bullseyed us...that was one storm that I did get a bit nervous about.  Opened the back porch door and shined a spotlight out onto a 75' or so pecan tree only to see it's top bent over by the wind touching the ground...I closed the door and high-tailed it back to the interior hall.  But, when the first eye wall passed us and we were in the eye I went outside and it was as calm as could be (except for my daughters and wife yelling at me to get back inside! :lol:).  The big pecan tree and a cousin of it both had one side of their rootballs pooched up about a foot or so above ground level.  I went back inside, we passed through the other eyewall and the storm started up again.  Both pecan trees were on the ground the next morning, roof damage, a good bit of timber damage.  I don't want to see that again.
Title: Re: Davis VP2 Rain Gauge
Post by: Intheswamp on June 30, 2018, 10:17:29 AM
I didn't want to leave everyone in suspense so here is an update. :lol:

I just punched the button on a Rainwise 111 gauge.  It'll probably be here the end of next week and hopefully I'll get it installed in a reasonable length of time (I tend to drag my feet sometimes :roll: ).

Has anybody added bird spikes to a Rainwise 111???  I'm sold on them after using the hour-glass, spike-ringed Davis buckets.

Any other modifications that would be good?

Thanks!
Ed
Title: Re: Davis VP2 Rain Gauge
Post by: JCA433 on June 30, 2018, 11:44:22 AM
The tipping bucket rain gauge part of my VP2 weather station also drastically measured less rainfall compared to the CoCoRaHS rain gauge by about 20 percent.  The recent adjustments I made seemed to have improved the performance to the point that both the VP2 rain gauge and the CoCoRaHS rain gauge are within 4 percent.  However it is too soon to be sure if the VP2 rain gauge will continue to perform well.  Here are the results over the past ten days.


CoCoRaHS gauge             VP2 rain gauge
0.01 inch                                  0
0.01 inch                                 0.01 inch
0.06 inch                                 0.06 inch
0.46 inch                                 0.48 inch
0.01 inch                                 0.01 inch
0.29 inch                                 0.33 inch
0.09 inch                                 0.09 inch
0.15 inch                                 0.15 inch
0.25 inch                                 0.26 inch
0.17 inch                                 0.18 inch
   
Title: Re: Davis VP2 Rain Gauge
Post by: JCA433 on June 30, 2018, 12:09:52 PM
I still do not trust the VP2 rain gauge because the mounting pole movement during strong winds increases the error.  Somehow I must prevent the  mounting pole from moving if the rain fall measurement will ever be reliable.  However at least the rainfall measurements are closer.


I forgot to mention that I also replaced the temperature and humidity sensor because it did not for some reason measure humidity over 90 percent.    The new sensor is model 7346.070.  The humidity is often very high here in Miami Dade Florida and maybe this wears out the senor over time?
Title: Re: Davis VP2 Rain Gauge
Post by: ValentineWeather on June 30, 2018, 01:16:10 PM
Good deal Ed. You will like the Rainwise. Also glad to see the Davis more accurate after calibration but like JCA433 mentioned the mounting will always be an issue and real test will come with bigger rainfall amounts.

My Texas electronics is main tipping bucket primarily because it has the heater. I trust the Rainwise just as much maybe more  because the TE seems to loose calibration with temperature changes. It works fine in summer but as temps fall calibration gets off while the Rainwise holds calibration down to freezing well. 

Todays rain all gauges were the same TE top gauge Rainwise bottom and both Cocorahs, NWS 8" all came in at .63. This was result when heavy rain doesn't fall the tipping buckets keep up well. 

Just so everyone knows I use a professional calibrator made by Novalynx and go with the recommended rainfall/rate they suggest on tipping bucket gauges. 
Edit: They suggest the 4" per hr. rate which seems high but results speak for itself.
Title: Re: Davis VP2 Rain Gauge
Post by: CW2274 on June 30, 2018, 02:55:54 PM
I just punched the button on a Rainwise 111 gauge. 
=D> Get it level and solidly placed, it'll reward you with excellent accuracy for a tipper.
Title: Re: Davis VP2 Rain Gauge
Post by: CW2274 on June 30, 2018, 02:57:42 PM
I forgot to mention that I also replaced the temperature and humidity sensor because it did not for some reason measure humidity over 90 percent.    The new sensor is model 7346.070. 
You're gonna love the SHT31. Don't forget the offset if needed.
Title: Re: Davis VP2 Rain Gauge
Post by: Intheswamp on June 30, 2018, 10:22:02 PM
Thanks for the feedback, everybody.  The VP2 ISS is mounted on a 4x4 post so I'm figuring on mounting the Rainwise gauge to the backside of the post.  Will figure out a shelf system for it that is stable.  I'm looking forward to it.  I also need to replace the temp/humidity sensor....got the SHT31 in a box here...somewhere. :roll: 
Title: Re: Davis VP2 Rain Gauge
Post by: DRoberts on July 06, 2018, 01:52:32 PM
Realizing that one measurement does not lead to an indisputable conclusion, I was a bit surprised when both my CoCoRaHS and VP 2 gauges agreed on .29" in a fast hard rain (duration 16minutes).

Usually the CoCoRaHS measures less than the tipping bucket.

Title: Re: Davis VP2 Rain Gauge
Post by: BigOkie on July 06, 2018, 04:35:55 PM
Realizing that one measurement does not lead to an indisputable conclusion, I was a bit surprised when both my CoCoRaHS and VP 2 gauges agreed on .29" in a fast hard rain (duration 16minutes).

Usually the CoCoRaHS measures less than the tipping bucket.
Interesting. The tipping bucket theory states that the bucket reading should be less.

Sent from my MHA-L29 using Tapatalk

Title: Re: Davis VP2 Rain Gauge
Post by: Intheswamp on July 06, 2018, 04:40:18 PM
Realizing that one measurement does not lead to an indisputable conclusion, I was a bit surprised when both my CoCoRaHS and VP 2 gauges agreed on .29" in a fast hard rain (duration 16minutes).

Usually the CoCoRaHS measures less than the tipping bucket.
Interesting. The tipping bucket theory states that the bucket reading should be less.

Sent from my MHA-L29 using Tapatalk
The Davis reading less is what I found when I set up the Cocorahs....and that's what prompted me to order the Rainwise bucket.

Btw, the bucket arrived yesterday....hopefully in the next week or so I'll figure out a mounting system for it...
Title: Re: Davis VP2 Rain Gauge
Post by: CW2274 on July 06, 2018, 04:44:55 PM
Realizing that one measurement does not lead to an indisputable conclusion, I was a bit surprised when both my CoCoRaHS and VP 2 gauges agreed on .29" in a fast hard rain (duration 16minutes).

Usually the CoCoRaHS measures less than the tipping bucket.
Interesting. The tipping bucket theory states that the bucket reading should be less.

Sent from my MHA-L29 using Tapatalk
The Davis reading less is what I found when I set up the Cocorahs....and that's what prompted me to order the Rainwise bucket.

Btw, the bucket arrived yesterday....hopefully in the next week or so I'll figure out a mounting system for it...
Are you going to hard wire it to the ISS?
Title: Re: Davis VP2 Rain Gauge
Post by: DRoberts on July 06, 2018, 04:54:22 PM
I will have to do a more complete comparison of the two.  My previous post was based on the few observations I have had the opportunity to make. It doesn't rain that often here, and I have had my station operational only since 27 May.

I don't think I have a siting problem with my CoCoRaHS, But I have been wondering about that ash tree.



Title: Re: Davis VP2 Rain Gauge
Post by: Intheswamp on July 06, 2018, 05:04:21 PM
Realizing that one measurement does not lead to an indisputable conclusion, I was a bit surprised when both my CoCoRaHS and VP 2 gauges agreed on .29" in a fast hard rain (duration 16minutes).

Usually the CoCoRaHS measures less than the tipping bucket.
Interesting. The tipping bucket theory states that the bucket reading should be less.

Sent from my MHA-L29 using Tapatalk
The Davis reading less is what I found when I set up the Cocorahs....and that's what prompted me to order the Rainwise bucket.

Btw, the bucket arrived yesterday....hopefully in the next week or so I'll figure out a mounting system for it...
Are you going to hard wire it to the ISS?
Yeah, hardwired to the ISS and just have the Davis bucket for back-up (if ever needed) and for spider housing. :-)
Title: Re: Davis VP2 Rain Gauge
Post by: Intheswamp on July 06, 2018, 05:05:48 PM
I will have to do a more complete comparison of the two.  My previous post was based on the few observations I have had the opportunity to make. It doesn't rain that often here, and I have had my station operational only since 27 May.

I don't think I have a siting problem with my CoCoRaHS, But I have been wondering about that ash tree.
Keep an eye on it and let us know how it goes.  It seems, from what I've seen, that the usual result is as we mentioned...Davis records lower than the Cocorahs gauges does.
Title: Re: Davis VP2 Rain Gauge
Post by: CW2274 on July 06, 2018, 05:17:57 PM
Realizing that one measurement does not lead to an indisputable conclusion, I was a bit surprised when both my CoCoRaHS and VP 2 gauges agreed on .29" in a fast hard rain (duration 16minutes).

Usually the CoCoRaHS measures less than the tipping bucket.
Interesting. The tipping bucket theory states that the bucket reading should be less.

Sent from my MHA-L29 using Tapatalk
The Davis reading less is what I found when I set up the Cocorahs....and that's what prompted me to order the Rainwise bucket.

Btw, the bucket arrived yesterday....hopefully in the next week or so I'll figure out a mounting system for it...
Are you going to hard wire it to the ISS?
Yeah, hardwired to the ISS and just have the Davis bucket for back-up (if ever needed) and for spider housing. :-)
You'll like it. I eventually removed the stock bucket and tipping mechanism, not necessary but I didn't see any reason to leave it there, just ma nature's junk collector.
Title: Re: Davis VP2 Rain Gauge
Post by: Old Tele man on July 06, 2018, 05:49:21 PM
For everyone operating both CoCoRaHS and Davis tipping units, here's a post asking for your help/input:

http://www.wxforum.net/index.php?topic=34669.0