Topic: Davis 6163 Purchase w/Questions

[Coolerman]

 
I have been reading on this site for awhile in preparation of ordering my first PWS. I will be ordering the Davis 6163 VP2 Plus.

One of the many questions I will have involves how high to mount the anemometer at MY location. I live WAY out in the country on 2 1/2 acres of farm land that is grass only, NO trees, at least within 800 to 1000 '. The land around my property is quite hilly. The house is located on the side of one of these small hills. The land falls away from the house on the North, South, and West, but climbs gradually on the East to a point maybe 35 feet higher over a distance of maybe 750 feet from where I want to mount the anemometer. As I said, no obstructions of any kind. The prevailing winds are from the West and South.
I have a fence on every side of the house with nice sturdy fence posts. My first idea is to mount a 10' section of chain link top post pipe to one of the fence posts resulting in the anemometer being about 12' in the air and mounting the ISS to the post 5' off the ground. I would of course drive in an 8' ground rod and ground this pole. This location is 150 feet to the north of the house and I have an upstairs window facing that direction where the console will be located. Easily in range for the Davis.
 
Any one see any issues with getting accurate readings at 12' in my location? I have no issues with getting it 33' off the ground, but that will require a bit more thought and expense to make it easily accessible for replacement and there seems to be some thought that 33' is not necessary for a PWS even if reporting the data to various online sites. I eventually plan to possibly add a wind turbine to this site depending upon the data I get from the anemometer.

All thoughts and comments welcome.
   
   

[ValentineWeather]

If  unobstructed you will still get good wind even at 12' just not the best. Here is one of my stations setup at about 15' it comes close to AWOS winds even sometimes exceeding the airport located in large open pasture with horses. This is about 150 yards from Console.

Weather underground link if you want to check historic data on wind. https://www.wunderground.com/personal-weather-station/dashboard?ID=KNEVALEN3

[ocala]

I think you would do fine at 12ft. You said the prevailing winds are from the west and south and also the land in that direction is on a down slope from the house. So if you take that lowest point from where that land levels out as compared to where your anny is it will be much higher then 12 ft.
You have a problem most of us would love to have. 
 In the end if you feel you can do better a telescoping poll will get you higher.

[dalecoy]

Put it where you can best measure the weather parameters that are significant to you.

I would personally agree with the positioning you have mentioned (5 ft and 12 ft).

And I wouldn't personally bother with a ground rod.  (A direct strike will fry things regardless).  You haven't said whether the existing fence is wood or metal, but (in my opinion) that's probably not a big factor, either.  However - a ground rod may "feel good".

[Coolerman]

I know, I do have a great site for weather monitoring.    Far better than when we lived in the city (Lexington) and had 75' trees surrounding the house on three sides!

The fence consists of wood poles with 4"x 4" welded metal wire between them. Typical cow fencing. I will ground the pole via a ground rod and bond the fence to the rod also. That way should the pole be struck (goodbye weather station!  ) the charge will be mostly delivered to the ground and someone who happened to be touching the fence a mile away (fences are all interconnected around here) might have a better chance of survival. Like was said, it will make me feel better.

I am searching the site for more pole information... Wealth of knowledge here if you dig for it...

[dalecoy]

You mentioned chain link fence top rail.  The heavier grade of that will work well in your application.

[ValentineWeather]

If you want to go higher the heavy gauge telescoping tele-pole is an idea. Some go with the 25',  I went with the 30' at my home station. Not the ranch station I posted above. I no longer see the 25' pole.

Link to telepole: The 20' superior 2 would withstand the highest winds of the 3. Only because it doesn't go as high as the 30' superior 3. I've had 62 mph gust not sustained on my 30' pole.

http://www.tele-pole.com/flagpoles/superior-2-flagpole/

[Coolerman]

If you want to go higher the heavy gauge telescoping tele-pole is an idea. Some go with the 25',  I went with the 30' at my home station. Not the ranch station I posted above. I no longer see the 25' pole.

Link to telepole: The 20' superior 2 would withstand the highest winds of the 3. Only because it doesn't go as high as the 30' superior 3. I've had 62 mph gust not sustained on my 30' pole.

http://www.tele-pole.com/flagpoles/superior-2-flagpole/

Ouch! That Tele-Pole, while a really nice pole, is a bit out of my price range! I was thinking more in the range of $75.00 - $100.00 for a 25' flagpole. I have to have some money left in the budget for whatever software and web interface I decide on.

A 25' flag pole would be perfect as I could mount it to the side of the fence post and get the anemometer up to a height of 27-28 feet. They are fairly cheap on E-Bay, in the $75.00-150.00 range. However...

If this pole can supposedly, carry a 3'x5' flag in 50 MPH winds without breaking  (no mention of how far it will BEND in said wind...) surely it could carry a anemometer at 50 mph without too much sway being as the drag would be MUCH less than a flag? I could easily attach guy wires to the fence if sway became a issue but how much would sway affect the readings?  Not much data on sway affecting readings that I have found so far.  Any links or thoughts on this?

We can get winds in the 50-60 mph range during storms (according to the local weather). I want to see how high the winds really blow here as I think being close to the top of the hill the winds are really stronger than that.  Yet another reason to get the anemometer as high as is feasible.

[dalecoy]

One question would be how much stress and wiggling you can safely put on the wooden fence post (and its surrounding soil).  My feeling is that - if you want to go much above a 10 ft. pole - you should consider a cement anchoring with a ground sleeve. 

[ValentineWeather]

Just showing options. I would stay away from the cheap flag poles you mentioned unless planning on guy wires or staying at 20' max. I did some research prior to my purchase looking at wind load not only on telescoping but solid flag poles and towers. Going lighter than 10 gauge aluminum was risky even at 25'. 
Some areas rarely see 50 mph winds so each circumstance needs looked at separately. I can experience 45+ several times a month so the lighter gauge poles was out of the question.

[Coolerman]

Just found this thread here: http://www.wxforum.net/index.php?topic=22095.0;nowap  interesting thing about the sail boats....

I have found several threads dealing with this issue and it seems to be true that once you go above 20' you need much stronger poles.

The fence in the place I want to mount this has three 8" diameter fence posts that are ALL cemented into the ground as this is sort of a corner. Strength of these posts is not an issue.

I did find a 25', 6" diameter aluminum street lamp pole on Craigs list  for $150.00.  I bet he would take $100.00 for it. I would have to pour a concrete base for it with bolts embedded in the concrete to secure it, but it would be rock solid!  Would not be easy to get it up or down without lots of help...tallest ladder I have is 24'... I'll keep looking....

[ValentineWeather]

The reason I didn't go with a solid pole is the maintenance issue.
Nothing wrong with a cheaper grade telescoping at 15-20' if you are away from obstructions. They all need cemented in with provided ground sleeve.

[Coolerman]

Well... It's a done deal! I just ordered a Davis 6163 VP2 Plus with aspirated radiation shield and the Weatherlink IP kit from Scientific Sales!  I have spent days reading about the Davis software/hardware and came to the conclusion, that for me as a beginner, plug and play is the way to go. Should receive it by Friday and this weekend I will get it configured, and temp mounted to a fence pole, while I start on the permanent pole. 

I have decided to build my own mounting pole, and will strive for a 25-33' mounting height. Going for a tilt down style pole for easy mounting, and what little maintenance (knocking the ice off) the anemometer may require. 

I hope to not have too many questions concerning the configuration. Most of this seems to have been covered multiple times here on the forum.

[Coolerman]

I still try not to ask questions that can easily be answered by a search. Searching ALWAYS leads me to find other things I needed to know!

I also just ordered a 4" CoCorahs rain gauge to see how my Davis does in comparison. Have read many threads concerning the accuracy of the Davis gauge and how some believe they are coming from the factory with poor calibration. We will see how mine does fresh out of the box in comparison to the Coco gauge.

I plan to mount the Coco to a fence pole 5' away from the Davis. I don't want to mount it to the same pole to prevent any "shadowing", or splashing from occurring between the gauges, but want it close enough that they read the same amount of rain.

Now my first question: The instructions for the Coco gauge says to mount it 2' above the ground in a none developed area (my location) and 5' above the ground in a developed area. Why the difference in height?

[DaleReid]

I would think that 3' from edge of one gauge to the edge of the other, at exactly the same lip height, would be sufficient to avoid splatter/shadow effect.  5' and you will begin to risk having a wind blown variation during a heavy rain, which from observation you can see sometimes is only a few feet wide when it hits a wet surface such as a driveway and creates sort of cat's paws.

Pure speculation on my part but the difference in height probably relates to side winds causing variation, but I don't know.

Do they give parameters for what is 'developed' and what is 'undeveloped?'  What if you have three acres of back yard, all grass, and one shed at the side of the land.  When does it transition from prairie to developed?

Any one know for sure the logic or was it just someone's guess?

[Coolerman]

http://www.cocorahs.org/media/docs/CoCoTrainingSlideshow_v9.2A.pdf

This is where I got the mounting information. Seems that if your gauge will be near obstacles you should mount it higher. Maybe it's to help offset any shadowing that the obstacles could cause?

So if the Coco should be mounted at 2' in the open, and the Davis spec is 5', then I guess I will have to have a separate small pole for the Coco to stay within their guidelines for reporting. I will start taking measurements this evening after I mow to determine the best place for everything.

[dalecoy]

So if the Coco should be mounted at 2' in the open, and the Davis spec is 5', then I guess I will have to have a separate small pole for the Coco to stay within their guidelines for reporting.

1.  Are you going to be "reporting"?

2.  What is your objective?

If your objective is to compare readings with the Davis, then they should be mounted in close proximity, at the same height above the same ground cover.

[Coolerman]

I just spent a couple of hours reading about how rain gauges mounted above the ground all suffer from wind induced under reporting (the condition that affects gauge measurements the most), and that the higher the gauge is above the ground, the more the wind causes under reporting. Also, the golden measurement is the "pit" gauge, (actually mounted IN the ground), something I had never even heard of!  I am now informed!

http://www.tandfonline.com/doi/pdf/10.3137/ao.460202

Same report talks about tipping gauge errors, evaporation errors, water sticking to the gauge side and buckets, blah, blah, blah... Total errors when all that was taken into consideration were amazingly high.  As much as 20%!

So... I will mount my CoCo at 2', to meet the CoCoRaHS requirements, and the Davis at 5', to meet Davis's requirements for the temp and humidity sensors.

I don't suppose the Davis rain gauge can be detached and mounted separately?  If it could I would also mount it at 2'...

[miraculon]

I don't suppose the Davis rain gauge can be detached and mounted separately?  If it could I would also mount it at 2'...

Davis offers this:

http://davisnet.com/weather/products/weather_product.asp?pnum=7857

and they say this in the description:

Record rain data and transmit rainfall information using an Anemometer/Sensor Transmitter Kit (#6332), sold separately.

This implies that you can set this up as a "rain station" similar to a "wind" setup. Unfortunately, although the Console seems to support a rain station when I actually tried to use it as such, it didn't work. The response from Davis wasn't too encouraging.

Meteobridge PRO does support a "rain station" configuration. I am using it with my NovaLynx rain gauge.

If you simply ran the rain signal cable from the 7857 to the ISS RAIN socket from wherever you placed the rain gauge, it would work. The 40 ft length should give you some flexibility. In this case, the rain would be part of the normal ISS function and not require anything special.

Greg H.

[dalecoy]

So... I will mount my CoCo at 2', to meet the CoCoRaHS requirements, and the Davis at 5', to meet Davis's requirements for the temp and humidity sensors.

I don't suppose the Davis rain gauge can be detached and mounted separately?  If it could I would also mount it at 2'...

Yes, the rain gauge can be detached and mounted separately.  You would want to get an additional part or two (probably the Part #: 07342.074 base), depending on your preferences.  And would have to extend the wiring from the tipping bucket assembly.

But - why not just mount the entire Davis ISS assembly at 2 ft., to make it the same as the other gauge?

(And you didn't say what your objective is, nor if you are going to be reporting the CoCoRaHs readings in some way, or how you will be using them)

[Coolerman]

I do plan to join CoCoRaHS and report the rain data. I also plan to put the Davis data on which ever web sites I decide on after getting it setup and tested.

The reason I asked if the Davis rain gauge could be separated from the ISS, was to get it down to the "official" 2' height recommended by CoCoRaHS.  (I don't want the temp and humidity sitting at 2' as that would affect their readings.)  For comparing the two gauges, that would eliminate the height variable. I also plan to orient them on a north south line so that the prevailing winds would affect them equally.

I just thread the 6 page thread (http://www.wxforum.net/index.php?topic=27517.0) comparing different rain gauges and such. interesting reading for sure...

[miraculon]

Just remember that the support for the bottom of the rain gauge also holds the T/H shield and ISS bracket. (and solar/UV if you are so inclined). Hence, I mentioned the separate 7857 availability. You would basically not use the ISS's rain gauge and use the 7857 either with an Anemometer Transmitter (again the console support is "broken") or run the wire from this separate gauge over to the SIM board on the ISS.

Greg H.

[dalecoy]

I do plan to join CoCoRaHS and report the rain data. I also plan to put the Davis data on which ever web sites I decide on after getting it setup and tested.

OK, so let's try a couple of examples:

1.  Davis at 5', CoCoRahs at 2'.

A.  Always different measurements.  (Davis always less, but by differing percentages). 
     What do you conclude?  What do you report?
B.  Sometimes Davis is more, sometimes CoCoRahs is more.  What do you conclude?  Report?
=====

1.  Davis rain at 2' (T/H at 5'), CoCoRahs at 2'.

A.  Always different measurements (Davis always less, but by differing percentages). 
     What do you conclude?  What do you report?
B.  Sometimes Davis is more, sometimes CoCoRahs is more.  What do you conclude?  Report?

============================
Segal's law is an adage that states:

    "A man with a watch knows what time it is. A man with two watches is never sure."[1]

The mood of the saying is ironical. While at a surface level it appears to be advocating the simplicity and self-consistency obtained by relying on information from only a single source, the underlying message is to gently question and make fun of such apparent certainty – a man with one watch can't really be sure he knows the right time, he merely has no way to identify error or uncertainty.

I'm actually looking forward to your experiment.  The results (whatever they are) will be interesting.

[Coolerman]

I do plan to join CoCoRaHS and report the rain data. I also plan to put the Davis data on which ever web sites I decide on after getting it setup and tested.

OK, so let's try a couple of examples:

1.  Davis at 5', CoCoRahs at 2'.

A.  Always different measurements.  (Davis always less, but by differing percentages). 
     What do you conclude?  What do you report?
B.  Sometimes Davis is more, sometimes CoCoRahs is more.  What do you conclude?  Report?
=====

1.  Davis rain at 2' (T/H at 5'), CoCoRahs at 2'.

A.  Always different measurements (Davis always less, but by differing percentages). 
     What do you conclude?  What do you report?
B.  Sometimes Davis is more, sometimes CoCoRahs is more.  What do you conclude?  Report?

============================
Segal's law is an adage that states:

    "A man with a watch knows what time it is. A man with two watches is never sure."[1]

The mood of the saying is ironical. While at a surface level it appears to be advocating the simplicity and self-consistency obtained by relying on information from only a single source, the underlying message is to gently question and make fun of such apparent certainty – a man with one watch can't really be sure he knows the right time, he merely has no way to identify error or uncertainty.

I'm actually looking forward to your experiment.  The results (whatever they are) will be interesting.

Man with two rain gauges, and an OCD derived accuracy issue, will have no spare time... 

To answer, what I would report? CoCo to Coco site and Davis to where ever.

Seriously, after all the reading I have done here and elsewhere, I know the Davis will never be comparable in accuracy to the manual CoCo, which will never be as accurate as an 8" NWS gauge or the super expensive weighing gauge, but I believe one should at least make an attempt to get what you have as accurate as is possible for the environment it is sited on. Since I blew my budget on the VP2 system, I only have the CoCo gauge to compare it to, and many agree the CoCo gauge is "accurate enough for government work".  I'm not trying to compete with the NWS for accuracy! My site is WINDY! So I would like to experiment to see just how much wind affects the gauges. I probably need to have a second CoCo to use as a 'control' gauge sited outside the test area but close enough to see the same amount of rain. Then graph all three gauges over several months with wind data.

I'm getting ahead of myself. I need to get the Davis first and get familiar with it! Should be here today...

[dalecoy]

OK, great!

Note that the Davis part that I mentioned (Part #: 07342.074 base) - which is $20 - and some moving-around of parts, and a bit of wiring - would allow you to mount the Davis rain gauge at 2 ft. 

The 7857, at $100, just lets you do the same thing without as much work.

Question: at what time of day do you plan to always read the CoCoRahs?