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Author Topic: Questions about Davis VP 2 Siting  (Read 32656 times)

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Offline RioRanchoNMWeather

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Questions about Davis VP 2 Siting
« on: July 13, 2007, 03:59:41 PM »
I didn't know if it was best to add on to this string since it is the same subject or to start a new string.


It seems to me that right from the get go you are unable to get a perfect CWOP score with the Davis unless you make some changes mentioned earlier.
You can't mount the rain guage at 2' above grass and the thermometer 5' above grass when the rain guage is mounted on top of the thermometer.  I don't think the rain guage would work well if you mounted the unit upside down :)    Likewise, unless you buy the wireless addon for the anemometer you have to use the 40' cable that attaches the anemometer to the ISS.  I have written Davis and a NOAA contact about advice on how you can mount the anemometer 33' in the air and still reach the ISS which by definition can't be mounted on the same pole.  I am guessing if you had a fence  you could mount the 33' pole to the fence, run the wire down to the fence top, then across to the ISS so you wouldn't have the wire suspended in the air between the two.  I don't know how far from the anemometer mast you are supposed to mount the rain guage so it is not impacted by the "shadow" of the mast? 

So, even if I upgrade to the Davis, getting the Davis properly sited seems impossible by design??

Unlike some of you, I have a lot of space an no wife to harass me.  That gives me the flexibility to mount things pretty much anywhere, depending on what each device needs and the limits of how the Davis is made.

The problem I have with my Honeywell is that the wireless range is very limited.  Even after buying a USB hub to extend my USB length to get the display in a window with LOS to all of the sensors, I still lose contact with them.  It seems the wireless distances of the Davis are superior to the Honeywell but I don't know how far I can realistically expect the signal to reach?

My house is a story and a half located on the SE side of a hill where my current anemometer is placed.  The whole area around my house is covered with mature deciduous trees and I have planted many pine trees that will cause more problems over time.  If you look at this aerial photo, you can see that to the north I have a pond and the 10a next to that is wide open.  There is a buffer between the pond and the farmed area which would be ideal, but it is several hundred feet away and I don't want to have to buy a repeater and I am still stuck with the problem of how you can mount the ISS in a proper location and use the 40' cable??  BTW, the picture is several years old and the pine trees around the house have grown quite a bit since that picture was taken.

http://www.goldenpondfarm.com/farm_pictures/aerial_hobby_farm_photo.jpg

I would appreciate any thoughts or comments on my predicament.

Thanks,

Lew
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Offline niko

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Re: Questions about Davis VP 2 Siting
« Reply #1 on: July 13, 2007, 04:21:56 PM »
It's somewhat confusing when you post essentially the same question in multiple threads  :?

Offline RioRanchoNMWeather

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Re: Questions about Davis VP 2 Siting
« Reply #2 on: July 13, 2007, 05:00:32 PM »
It's somewhat confusing when you post essentially the same question in multiple threads  :?

Hmm...I don't think I repeated hardly anything here I posted elsewhere?  Maybe pieces of it, but I tried to put the bulk of my siting questions/issues in one place, and that was here.

Since this is the topic about siting the Davis this is where I wrote my question.  I did write on another topic about what station to buy but don't think there is any overlap with this point.  There was a topic I just replied to about taking the rain bucket off the ISS but I didn't ask about that here.

It might seem like it, but I don't think what I asked about here was asked in other threads?  Maybe I am more senile than I realized?

This is the only topic I am expecting siting answers to be posted on.  Seems there is a lot of interest in my equipment configuration topic and no interest in this topic.

Thanks,

Lew
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Offline looney2ns

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Re: Questions about Davis VP 2 Siting
« Reply #3 on: July 13, 2007, 06:39:17 PM »
Lew, It is obvious that when Davis went to the current "easy install" design they were not taking proper siting into consideration. They simply were making it as easy to install as possible for the majority of the people which equals more sales or so they surmised.

You do have a challenge in your situation. From the picture provided, I don't see you have much choice other than to use a repeater and move instruments to the open field. That is if you want as ideal siting as possible.



Offline RioRanchoNMWeather

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Re: Questions about Davis VP 2 Siting
« Reply #4 on: July 13, 2007, 07:11:12 PM »
Hiya...

It happens I called Davis tech support mainly in regards to the new topic I opened about the datalogger.  I think he didn't like my questioning their bundling so when I got to the question about separating the bucket and temp part he got downright defensive.  More or less implied they knew what they were doing it and built their device as it should be and I was more or less an idiot for considering taking them apart.  When I tried to bring up the issue of proper siting and how each device needed to be in it's best location, he more or less hung up on me.

I wasn't questioning their design.  It is obvious it was made for the easiest possible installation (all as one unit) vs. what was best for siting purposes.

If all three things had to be mounted together, they probably did as good of a job as could be done. It does seem to me that the rainbuck would be an interference to proper wind readings as their has to be some affect on wind direction, especially if the wind is coming from the bucket side. Likewise with windspeed...the bucket has to slow the wind down coming from the bucket direction.  Likewise, since the anemometer is above the bucket, it seems it would have some impact on getting the proper amount of rain in the bucket.  I guess having the bucket mounted higher than it should be, even if not at the top of a 33' mast, that the rain data isn't going to be as accurate as it could anyway.

Thanks,

Lew
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Offline looney2ns

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Re: Questions about Davis VP 2 Siting
« Reply #5 on: July 13, 2007, 07:31:48 PM »
You enjoy arguing, don't you.  :wink:
This is a hobbyist home owner type system. And that's the market they have always catered to for 20 years.

If you want a professional station that is designed for proper siting and not install convenience then purchase one of those. Such as: http://www.columbiaweather.com/WeatherStations.html

Hundreds of the Vantage Pro 2s I'm sure have been sold because of Brian and WD and this forum, your going over the same ground that has been discussed numerous times on here. I'm betting the 99% of those folks are completely happy with their Davis purchase. You really should step back, take a deep breath and just enjoy the hobby, and stop obsessing so much about it. It's JUST a hobby.....well for most of us anyway.

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Re: Questions about Davis VP 2 Siting
« Reply #6 on: July 13, 2007, 07:45:41 PM »
I would appreciate any thoughts or comments on my predicament.

You have a choice...you either save money and live with a compromise or spend the money buying the right equipment to get as near perfect an installation as possible. Davis sell the equipment you need, but you don't seem to want to spend the money to go for 'near perfect', so I guess you have to decide what you're prepared to compromise on. To be honest you are in an unusual situation compared to the vast majority of Davis VP2 owners and whilst Davis could improve the separation of their equipment the station would then cost more and the changed features wouldn't be used by many people anyway. Bundling 100ft of cable for the few people who could use it would be an extra cost I (and others) wouldn't want. I know I can't have a perfect meteorological installation at my house, so I live with what I can do (at a cost I can afford). The VP2 does have some compromises, but even if I could, for example, separate the rain gauge and temp sensor by a few feet I wouldn't actually have a better place to mount it.
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Offline RioRanchoNMWeather

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Re: Questions about Davis VP 2 Siting
« Reply #7 on: July 13, 2007, 08:34:14 PM »
Hiya..I am hoping to turn the hobby aspect of it into a business.  I am hoping to incorporate the weather data into a part of a community resource (a different website) that will possibly earn money for me by selling ad space.  The site will have local news, weather, events, and sports information as well as pictures, etc.  I am hoping the website will have enough traffic to justify people paying to place ads on it much like the local newspaper does on their site. 

I want to do things as good as possibly can be done within a reasonable cost.  I was hoping the Honeywell unit would be good enough and didn't want to spend the extra money for the Davis and have to get rid of the Honeywell now too.

I have a couple more pictures showing my current configuration.  After building the solar screen for my temp sensor I found it wouldn't sync from there so after building the contraption I was unable to use it....(sigh).

http://www.farmingtonweather.com/pictures/anemometer.jpg

http://www.farmingtonweather.com/pictures/uvrain.jpg

Thanks again!  I am going to leave for awhile and take a few breaths.

Lew
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Offline sloweather

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Re: Questions about Davis VP 2 Siting
« Reply #8 on: July 13, 2007, 08:39:00 PM »

It seems to me that right from the get go you are unable to get a perfect CWOP score with the Davis unless you make some changes mentioned earlier.
.....
I would appreciate any thoughts or comments on my predicament.


Again, I'm puzzled by the quest for a perfect CWOP score. If CWOP is all that great at calculating what the weather conditions should be where you are, forget the weather station and figure out how to get them to calculate your weather data for you. Carried to its illogical conclusion, CWOP would only need one weather station in the country, and then be able to calculate the conditions for everywhere else.

The truth is, weather conditions are just too variable for their numbers to be more than a general guide. Right now, here, there is almost a 10 degree difference across 300' horizontally/100' vertically from up here at the house to down in our woods.

And, based on your photo and description, the weather station itself is the least of your siting troubles.

You can extend the Davis wired anemometer more than 40'. I've done it. Mine is at least 140'. There is an app note on their site about how far it can be extended, and how the distance affects the top measurable wind speed. You can also extend the cable from the wired ISS to the console. I've forgotten exactly how far Davis says it will go, but I believe the spec for the protocol they use is 4000'. My farthest console (I have 2 in a daisy-chain) is at least 300 cable-feet from the ISS.

Learn to compromise, or drop a wad of cash to do it "right".
SLOweather Chris

Offline administrator

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Re: Questions about Davis VP 2 Siting
« Reply #9 on: July 13, 2007, 08:50:13 PM »
I want to do things as good as possibly can be done within a reasonable cost.

A VP2 installed in the normal way, including compromises on siting, is probably as good as you need to go if it's just for public information purposes. If you tell people it's 82degF when it's between 77 and 87 degF most people won't argue (unless they have an accurate screened thermometer and are hoinding it right next to your temperature sensor). Same for wind speed...people think in terms of how windy it is at 5-6 feet off the ground, not whether it's exactly 27.9mph 30ft up in the air. Even the tallest man in the world is still more than 20ft short of having his head in the winds at 30ft! You probably pass numerous big temperature signs as you drive around your area...I'd like to bet their sensors aren't located in anything like the ideal positions, but people still look at them and believe that they're telling the right temperature. Did you ever consider how accurate the temperature on those big signs was until you tried siting your own station? Probably not, but you probably have taken the temperatures as being reality.

I'm not suggesting you make numbers up...just that you may be striving for a level of perfection that your audience doesn't need (or even know it needs). For example, I know that some people use the data from my station, despite it's compromised siting and the people who have used it have never asked how well it's sited!
Chris
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Offline niko

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Re: Questions about Davis VP 2 Siting
« Reply #10 on: July 13, 2007, 11:04:44 PM »
If all three things had to be mounted together, they probably did as good of a job as could be done. It does seem to me that the rainbuck would be an interference to proper wind readings as their has to be some affect on wind direction, especially if the wind is coming from the bucket side. Likewise with windspeed...the bucket has to slow the wind down coming from the bucket direction.  Likewise, since the anemometer is above the bucket, it seems it would have some impact on getting the proper amount of rain in the bucket.  I guess having the bucket mounted higher than it should be, even if not at the top of a 33' mast, that the rain data isn't going to be as accurate as it could anyway.

Thanks,

Lew

You don't have to mount the bucket and the anemometer together. Although I admit you do see pictures with it that way, the typical single pole install will put the anemometer a lot higher on the pole than the rain gauge, and that should be satisfactory for most purposes. In the standard station package the anemometer comes with a 40' cable and the necessary U bolt for it to be mounted separately.

Offline looney2ns

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Re: Questions about Davis VP 2 Siting
« Reply #11 on: July 13, 2007, 11:27:25 PM »
Lew, if you want more siting options, this is the station I use.
It is considered semi-pro.http://www.txwx.com/

It is the station of choice for such places as the FAA and NASA among others.
http://www.txwx.com/customer.html

I own two of them, and one of them is approaching 10 years old. Had very good luck with them.

Re: Questions about Davis VP 2 Siting
« Reply #12 on: July 13, 2007, 11:57:11 PM »
I opted for the "up, up and away" approach to mounting my Davis VP2.  My thought was;  I'd rather lose some temperature accuracy (although I don't see how raising the temp. sensor above 5' does that) to ensure a good wind and rain reading.

I ended up mounting the ISS about 25 feet in the air (on an old bird house pole):

Click photo to enlarge:



The temp. readings don't seem to suffer (these are unadjusted CWOP readings):



Just a thought...

« Last Edit: July 14, 2007, 04:09:45 AM by anchorageweather »
South of the Tracks, Anchorage, KY

Offline niko

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Re: Questions about Davis VP 2 Siting
« Reply #13 on: July 14, 2007, 12:12:12 AM »
There is a difference, this station plots both 2 meter and 10 meter temps.

Offline RioRanchoNMWeather

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Re: Questions about Davis VP 2 Siting
« Reply #14 on: July 14, 2007, 02:15:01 AM »
You don't have to mount the bucket and the anemometer together. Although I admit you do see pictures with it that way, the typical single pole install will put the anemometer a lot higher on the pole than the rain gauge, and that should be satisfactory for most purposes. In the standard station package the anemometer comes with a 40' cable and the necessary U bolt for it to be mounted separately.


It seems if you are going to use a single pole, you have no choice but to put the whole mess at the top.  If you try to mount the rainbucket further down on the same pole, i.e. 2' above the ground, the pole itself will block the rain and perhaps cause some sort of swirling action?  That is why I though you would need the 33' pole for the anemometer and another pole some distance away with the rest of the stuff on it or perhaps three poles.  The short one for the bucket, the medium one for the temp, and the tall one for the anemometer.  If you also had a solar or UV sensor you wouldn't want a pole shadow to fall across it so it would probably be on your tallest pole too.  It looks like in your picture that you have bushes around the pole taller than the pole?  That is my problem...the trees near my current pole aren't taller but will be in a matter of a few years and there are trees further away that are 60-80' tall so I just need to stay a long ways from them.  I saw a formula somewhere for how far you needed to be away from taller things to reduce or eliminate any interference? 

I could be wrong, but it seems that air temp is about the only thing that wouldn't be as sensitive to location as other readings?

I had an errand this afternoon so I though I would drive by the two stations nearest to me to see what their equipment was and how they had it sited.

The first stop was the area airport.  The CWOP map shows their WS in the middle of the runway which I knew wasn't likely.    Turned out there weather station was several blocks away and didn't even appear to be on the airport property.  Was in a cornfield near a cemetary.  I couldn't get there from the airport so I thought I would pay it a visit some other day. 

The other site I stopped by was the closest personal station, a Davis.  They guy had it mounted on his chimney.  It was one of those fake chimneys that doesn't even extend above the apex.  His station was on a short pole and his non-aspiriated temp sensor wasn't even a foot above the roof, if even that.  So his sensor was non-aspirated and had to be consumed by heat from the brown shingled roof.  The only saving grace was it was a 2-story house so there was probably some wind.  I am guessing he was either relinquishing to the better half or wanted his station to be "low profile".  Also, not more than 20' or so away was a tree taller than the roof of his house.  On my next jaunt I will go by the other airport just south of me and another person station just north of me.  The one north of me has problems.  The CWOP map shows his registered location and his APRS location to be .9 mile apart?  I don't know how APRS knows such things? 

Anyway, his barometer is WAY off....he not only gets two thumbs down in MADIS, but his site stands out like a sore thumb compared to other stations in the area.

Anchorage,  my current anemometer is mounted on a old Martin house pole that was in the yard.  The Martin house got ripped off when what I think was a tornado came through, or nearly through.

I think you are also sacrificing your rain reading as supposedly there is more wind the higher you go and the higher wind keeps all of the rain from falling into the bucket?

I saw those quite elaborate fence looking things people have mounted around their rain buckets.  In fact, I think they were actually a commercially made product to block "all" wind from reaching the bucket.

Thanks again guys,

Lew
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