Author Topic: Another WMR200 vs. Davis Vantage Pro 2+ discussion  (Read 12656 times)

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Offline 71sbeetle

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Another WMR200 vs. Davis Vantage Pro 2+ discussion
« on: July 09, 2008, 11:15:21 PM »
Alright, so we just bought a house and I decided to set up a new weather station. I used to have a WM918 but sold it a few years ago when we last moved. I was thinking of picking up the WMR968 but saw the newer WMR200A and it caught my eye. Now reading a lot of stuff online I find most people prefer the Davis VP2/VP2+ over any OS stuff.
I am planning on having the station at my house, the temp sensor will be in a shaded area about 6ft off the ground, on a side wall of the house, the rain sensor will be in the most open area of my backyard and the anemometer will be at least 7ft higher than the roof. I am also planning on having one extra temp/humidity sensor as well as a temp sensor for my pool.
Now all of that would cost me well under $600 using the OS WMR200 with extra temp/hum sensor and the new pool sensor (compatible with the WMR200) and VWS Internet version, but if I got the VP2+ and software/serial cable, extra sensors, VWS etc I would be well over $1200 !!! More than double the price.
I have narrowed it down to a couple of pros and cons on each station:

WMR200:
Pros:
- Cheaper
- Easy to use pool sensor
- Extra sensor are cheaper to buy
Cons:
- Wind reports only every 14 seconds
- Sensor accuracy
- Forecast calculations based on barometer only
- Customer support

VP2+:
Pros:
- Better quality
- Greater range
- Better forecast algorithm calculation
- More accurate
Cons:
- Price
- Pool water temp sensor not easy
- no 24hr vent fan with cabled station
- USB or Serial connector expensive to buy and required to connect to computer

What do you recommend ?

Offline Anthony

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Re: Another WMR200 vs. Davis Vantage Pro 2+ discussion
« Reply #1 on: July 10, 2008, 08:29:59 AM »
To me is comes down to this, money & accuracy. Now if I had the money I would deffinately get the Davis. If you have not checked Ambient Weathers prices I suggest you do so. Make sure you have them e-mail you there low price quote. Last time I checked you could purchase their basic wireless station with the datalogger (required to connect station to computer). You could get the station for less than $600.



Thanks,
Anthony
WB8YUE

Offline 71sbeetle

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Re: Another WMR200 vs. Davis Vantage Pro 2+ discussion
« Reply #2 on: July 10, 2008, 11:25:47 AM »
Hi !
Thanks for the answer. Well I figured if I was going thru the trouble of installing Davis' water temp sensor I would get the VP2+ and a 24hr FARS, unfortunately they dont make a station with 24hr FARS that is cabled (which I believe would make it cheaper). The prices I quoted above are the ambientweather low prices btw :) I just wish that Davis would add a floating pool sensor to the sensor lineup :)

Offline Carson Weather

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Re: Another WMR200 vs. Davis Vantage Pro 2+ discussion
« Reply #3 on: July 10, 2008, 12:47:26 PM »
I've had an OMR-968 for 5 years.
I just bought a VP2 wireless w/24hr fan. I am considering returning it.

The inability to separate the rainbucket from the temp sensors from the solar power makes it difficult for me to use.

Accuracy of temps, humidity, and pressure seem to track equally on both stations.
Wind is updated more frequently on the VP2, but wind readings also track closely on both.

Although I haven't spent a lot of time with the VP data logger, the fact that it logs conditions when the VP console is disconnected from the PC has also caused a few problems -Ex. When resetting pressure, the default/ambient pressure is stored as sea level pressure and then transferred to the PC sea level pressure.
« Last Edit: July 30, 2008, 04:22:51 PM by Carson Weather »

Offline tinplate

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Re: Another WMR200 vs. Davis Vantage Pro 2+ discussion
« Reply #4 on: July 10, 2008, 12:52:14 PM »
Quote
Although I haven't spent a lot of time with the VP data logger, the fact that it logs conditions when the VP console is disconnected from the PC has also caused a few problems -Ex. When resetting pressure, the default/ambient pressure is stored as sea level pressure and then transferred to the PC sea level pressure.

I don't understand what the problem is you're describing.

Offline Carson Weather

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Re: Another WMR200 vs. Davis Vantage Pro 2+ discussion
« Reply #5 on: July 10, 2008, 01:03:31 PM »
I'm using VWS.
Local pressure is 25.00in
Seal Level pressure is 30.00 in
If I "default" my Davis VP2 console, pressure shows up as 25.00in. I then manually change the VP console to show the correct 30.00.
Once I connect the console to my PC, my software shows that I have had an abnormally low seal level pressure of 25.00in.

If that doesn't make sense (an no one has ever accused me of making sense :) ) , lets just say that I'm accustomed to disconnecting the console from my PC and "playing" with the sensors.
With the 968 I can place the temp sensor in different areas of my property to get an idea of where the sensor should be located and not have to worry that the "test" data will then be downloaded to my software. -

The VP2 SAVES data and then downloads, the OMR968 just passes it on as it happens.

Offline Garth Bock

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Re: Another WMR200 vs. Davis Vantage Pro 2+ discussion
« Reply #6 on: July 10, 2008, 01:16:47 PM »
I had an O/S WMR968 for several years and just recently got a Davis. I loved the O/S's touch screen. Hey anything with a touch screen these days is cool....lol. I wasn't concerned with accuracy and it worked well. The mounting of the outside transmitters were just plain ugly. I over looked it and used lots of cable ties. Even though the plastic yellowed in the sun the transmitters worked ok until the plastic posts that joined the body of the transmitters to the swivel mounts began to fail. All of a sudden I had transmitter heads hanging from the sensor cables. I took a different route when I bought my Davis wireless VP2. I bought an ISS separately from my Envoy. Next purchase will be the solar sensor. OK I know I will spend more in the long run but my immediate out of pocket is less of an impact. I don't need the console because I am displaying everything on the computer. I originally had a USB dataloger but it quit working after a weather software upgrade. Both work and mine are serial loggers. I like the ISS since it is one compact (?) unit to mount. The company I bought from has good prices and I also watch eBay. Now what software should you run ? That's a whole 'nother message and lots of opinions......

Davis VPro2,VWS,WL,VVP,WD,WDL,Cumulus,WV32,VPLive

Offline tinplate

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Re: Another WMR200 vs. Davis Vantage Pro 2+ discussion
« Reply #7 on: July 10, 2008, 02:11:42 PM »
I'm not sure I'd call that a problem with the VP2. The data logger stores the data. The weather software downloads it. Many weather programs let you choose whether or not they will download the archive data when they reconnect to the data logger. Nothing inherent in the VP2 or the data logger forces connected programs to download the data stored there.

As for the barometer, if you are using the adjustment (up down arrow keys on the console) to change the display from displaying raw pressure to displaying sea level pressure, there is a better way to do that. Simply set the console's elevation to 0 ft. That turns off the sea level reduction algorithm inside the console and it displays the raw sensor pressure. Set the elevation back to your true elevation and the console will calculate and display the sea level pressure. Using the up/down keys to set the pressure should only be used to make minor calibration adjustments.

Steve
SoftWx

Offline Carson Weather

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Re: Another WMR200 vs. Davis Vantage Pro 2+ discussion
« Reply #8 on: July 10, 2008, 02:40:32 PM »
Steve, thanks for the reply.
Regarding the data logger, no I wouldn't call it a problem, I just said it caused a few problems :)
As a "data logger" it's doing what it should. I just need to learn how to use it properly.  &^%$%# Learning Curves!!

I've been doing a lot of monkeying around with the barometer- Thanks for the tutorial, it makes sense, but I almost want to say that when I did it that way (including making the minor correction for what the VP says vs. what the local NWS says) the readings seemed to "wander". For the last several days I've left the altitude at 0 and it seems to track closer to the NWS station than it did before. I think. Or maybe it was the fact that it had only been out of the box for a few days and needed to acclimate....


Offline NiceBill

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Re: Another WMR200 vs. Davis Vantage Pro 2+ discussion
« Reply #9 on: July 10, 2008, 10:15:39 PM »

A barometer may not be not adjusted but is generally always acclimated, unless it is in a sealed plastic bag.

Bill.>>>>>>>>>>>>>>> :-)
[note: Bill passed away December 31, 2008 -- Rest in Peace Bill, you'll be missed!]

Offline tinplate

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Re: Another WMR200 vs. Davis Vantage Pro 2+ discussion
« Reply #10 on: July 10, 2008, 10:45:50 PM »
Very often, the value you see for NWS stations is altimeter. When you compare an altimeter value to a sea level pressure (SLP) at altitudes above 1000 ft as you are, your SLP will appear to wander. That's because the formula for deriving altimeter from the sensor pressure only takes altitude and sensor pressure as inputs. The formula for SLP takes altitude, sensor pressure, humidity and mean temperature (the average of the temp now and the temp 12 hours in the past) as inputs. As the average temperature changes, SLP will appear to wander compared to altimeter. But as you can see from the inputs, the two values are really quite different, so you're comparing apples and oranges.

Now, to make things even more complicated, the sea level reduction algorithm in the console is a little different than the one used by the NWS. So even comparing SLP to SLP may show a little wandering, but they should be close. In fact, there are several formulas for calculating altimeter, and several for calculating SLP. If you're curious, you can see some source code for the conversions here
http://www.softwx.com/weather/uwxutils.html
as well as links to the various sources for the formulas.

Steve
SoftWx

Offline Carson Weather

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Re: Another WMR200 vs. Davis Vantage Pro 2+ discussion
« Reply #11 on: July 10, 2008, 11:52:06 PM »
Now, to make things even more complicated, the sea level reduction ......
Steve
SoftWx

You said a mouthful there, brother.
Thanks for the link. I checked out your pressure calculator. I now feel a massive headache coming on. It's either all those calculations, or a low is coming in :)

Offline Carson Weather

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Re: Another WMR200 vs. Davis Vantage Pro 2+ discussion
« Reply #12 on: July 30, 2008, 04:28:19 PM »
After several weeks of playing with the Davis, hrere are a few thoughts/comparisons: (Old station was OS-968)

1. Davis has larger diameter rainbucket
I get minimal rain, so the rainbucket means little to me. I record via a manual 4" gauge. When you only get ~5' per year, you've got to be more accurate than the 20% error that I've seen on the OS (and read about on the Davis). I plan on calibrating the Davis for use in rain rate, but I'll continue to use my manual gauge for totals.

2.
Fan Aspirated temps.
I like the fact that this unit is fan aspirated. Due to my location in the desert, the fan does help, although the north facing, in the shade, side of my house where my sensors were mounted previously seems to read a degree or two cooler during daylight hours. (as an aside, I've placed an OS temp/hydro sensor in the shield and noticed that when temps are RISING, the Davis temp lags. When temps are FALLING, the Davis temp lags)

3.Console.
Both consoles are *fair* at reception. From my testing, it did not appear that the Davis signal was any stronger or traveled further than the OS.
The OS console sits on a shelf, out of view. The Davis console is on my desk right now, and while I like the continuous backlight ability and the ability to view daily, monthly and yearly high/Low, these are all things that I can see on my website and I'm sure the novelty will wear off soon.

4. Anemometer.
I like that the Davis reports to the console more often. I'm noting that max wind speeds are about 10% higher with the Davis. The big black cups are kinda cool too :)

5. Sensors.
I think that the "Integrated Suite" concept really lacks. I have several shaded areas at my location that would be better for temperature readings than in the full sun. I can't use them because the unit needs sunlight to charge the batts.
The  best location (temperature wise, in the sun) is also a poor location for the rain bucket.
I appreciate that the anemometer can be disconnected, but it's still a long way from the top of my roof to where the ISS is currently located.
Additionally, my OS indoor sensor is in a room of the house that is representative of the homes temperature. The Davis has no separate sensor, so my "indoor" temp is about the same as the air next to my PC where it's currently 87 degrees f.

6. Cost.
There is no comparison. I spent ~$650 for the Davis (FARS, no solar, Weatherlink). If I want to do the wind correctly, I need to spend another ~$150 on the wireless transmitter (I've got a 100' cord run down the roof now). That's $800 bucks. The OS968 (have they discontinued it yet?) is about $200 (and that $200 includes FOUR separate freestanding sensors, three of which are solar powered)
There is no way that I see a $600 advantage here.

7. Tech support.
For the most part, OS tech support does not exist
but
I've called Davis twice. The first time was the day I received it, and my call was in reference to pressure settings. I was told to let it "sit for a week" and normalize.
The second call was for siting issues (as described above). My name was taken and I was told to expect a call back with some suggestions. It's been 5 days and I have not heard back.

Offline NiceBill

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Re: Another WMR200 vs. Davis Vantage Pro 2+ discussion
« Reply #13 on: July 30, 2008, 07:47:37 PM »

So, why did you buy a Davis?  Sounds like you could get by with a rock and a string.

Bill.>>>>>>>>>>> :shock:
[note: Bill passed away December 31, 2008 -- Rest in Peace Bill, you'll be missed!]

Offline Carson Weather

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Re: Another WMR200 vs. Davis Vantage Pro 2+ discussion
« Reply #14 on: August 06, 2008, 12:18:01 AM »
As a matter of fact, I do have a rock and a string. They are now my *second* backup . If I could find a Rock=>Serial adaptor, they probably would be my primary.

I bought a Davis because:

1. In the past, I have lost communications with the OS temp and of wind appox once a month. Climbing up on the roof to press a reset button is dangerous, if not impossible in the winter. I figured saving my neck was worth the money.
FWIW, I've moved my OS Console to another area of the house (farther from the wind sensor) in May and have not had one lick of trouble from it . (The Davis has not lost comm either)

2. After 5+ years, I owed myself a "present" and from what I had heard, it would be a meaningful upgrade.

On the plus side, we has a party this weekend and the "What's that conglomeration of plastic on a pole in the middle of your backyard" questions, were great conversation starters. :)

-Joe