My Mobile Mesonet

[Joey Ketcham]

Been working on my mobile mesonet today, so far here's what I've gotten so far.

http://216.110.165.36/car1.jpg
http://216.110.165.36/car2.jpg
http://216.110.165.36/car3.jpg

[Greg Campbell]

What's with the large base rectangle? Are you planning to mount one of those TAP 2 state-of-the-art portable weather observatories? ;)

Seriously, what instruments are you going to install?

-Greg

[Joey Ketcham]

It's just gonna be a big dome on it, nothing inside of it.. just for looks mainly... just kidding. N o it's gonna hold my rain guage, gonna use it to mount my scanner antenna's on plus my anemomenter,a dome covered camera that I can control from inside the car that'll be hooked up to my laptop to record video and also a going to mount an external TV antenna onto it. Mainly just to keep it so I don't have to mount so much to my permanantly.

[Chris Sokol]

A quick heads-up...everybody that I have known that has used magnets to install there wx-station has had the same problem...gone with the wind. You definately need some type of strap system...Wal-Mart has a set of strap-on roof racks for $20. I had a station based on these for 3 years and never had a problem. Also, the foreward mast will need a brace running at an ange from the mast to the rack, and also one from the foreward section to the mast. PVC will flex and break if not braced. I am curious...is the mast where you intend to put the anemometer?

All in all, not a bad basic design.

[Joey Ketcham]

Thanks for the advise Chris, I know what you mean about weather stations that went "gone with the wind". About 6-7 years ago I made a weather station that was basically a single PVC pipe that held a anemometer and barometer and when I tested it.. of it went..

It's still in the workings, that was just what I got done yesterday, my weather station is coming in on Tuesday so I'm gonna finish it then.. including adding front brace supports to the mast

And yes, the front mast is where I'm going to be placing my anemometer at and across the base I will have a thick sheet of plexiglass that will hold other stuff.

[Greg Stumpf]

Originally posted by jketcham
Been working on my mobile mesonet today, so far here's what I've gotten so far.

The placement of your anemometer won't work. It is way too close to the vehicle chassis to get an accurate reading. You will be measuring air speed within the compressed airflow about the car - even if the vehicle is stationary (just think "wind tunnel"). In most situations, your measured wind speed will be an overestimate of the true wind.

NSSL engineers obtained information about the windflow about the vehicles that they mounted the mobile mesonets on. They found that the wind equipment had to be mounted pretty far away from the chassis in order to be effectively out of the vehicle airflow envelope. In later designs, this was about 3 feet high and 2 feet forward of the top side of the windshield.

Also, please strongly consider a weather logging system - make your observations useful to the rest of the community, either via post event logs, or via real-time reports to the NWS.


Greg Stumpf, Norman, OK

[Joey Ketcham]

Greg,

Thanks for the reply and for the advise. I never thought of the airflow and how it'd affect my readings.. but definately makes sense now and I'll get that corrected.

As far as a weather logging system, it's a done deal. I bought a software package with the weather station that will continuously log weather conditions in and around the storm onto my laptop and archieve it with time and date stamp so I will definately be contrubiting that info the NWS and to the rest of the community.


Joey

[Bill Hamilton]

Originally posted by Greg Stumpf
Also, please strongly consider a weather logging system - make your observations useful to the rest of the community, either via post event logs, or via real-time reports to the NWS.

Once he gets his HAM license it will make real-time reports easier to report to the NWS. As far as the mobile meso it will be refined and trustworthy by the next storm season I'm bet. Trial and error will work the kinks out but it is a good start. I am curious to see his final project.
I'm not to crazy about a sunroof in a storm chase vehicle because I have had one shatter before but that is another story. I would use film tint on it though to help keep you from wearing it.

[John Diel]

Just in case you are wondering, the principle associated with the anemometer placement and accurate wind reading is the Bernoulli Effect or Bernoulli's Law:

For horizontal fluid flow, an increase in the velocity of flow will result in a decrease in the static pressure. The equation describing this effect is known as Bernoulli's law. The most practical example of this is in the action of an airfoil. The shape of an airplane wing is such that air flowing over the top of the wing must travel faster than the air flowing under the wing, and so there is less pressure on the top than on the bottom, resulting in lift.

Looking at the Project Vortex stuff, they placed their meters 3 meters above the ground level (just over 9 feet). Depending on the vehicle I would think this was about 4 to 5 feet from the top of the vehicle roof. They also said they solved the issue of wind speed measurements while driving, but they didn't say how. I'm betting it was done post chase using the GPS info and vehicle speed rates in some formula.

John

[David Sallee]

Looks like a good start Joey.... I'm also interested in seeing the final project .... I'm going to be putting me together one this fall... hopefully.. :wink:

Dave

[David Drummond]

Originally posted by Greg Stumpf+--><div class='quotetop'>QUOTE(Greg Stumpf)</div><!--QuoteBegin-jketcham
Been working on my mobile mesonet today, so far here's what I've gotten so far.

The placement of your anemometer won't work. It is way too close to the vehicle chassis to get an accurate reading. You will be measuring air speed within the compressed airflow about the car - even if the vehicle is stationary (just think "wind tunnel"). In most situations, your measured wind speed will be an overestimate of the true wind.

NSSL engineers obtained information about the windflow about the vehicles that they mounted the mobile mesonets on. They found that the wind equipment had to be mounted pretty far away from the chassis in order to be effectively out of the vehicle airflow envelope. In later designs, this was about 3 feet high and 2 feet forward of the top side of the windshield.

Also, please strongly consider a weather logging system - make your observations useful to the rest of the community, either via post event logs, or via real-time reports to the NWS.


Greg Stumpf, Norman, OK[/b]

Hey Greg, I know we had discussed some of this via email...I am wondering.....do you guys have ability to see APRS up there? I know some SKYWARN groups use it and if I remember right you can hook APRS up to a wxstation like a mesonet and broadcast that out with it. I seem to remember they guys at MAF telling me they liked seeing all the stationary ones in the area as it was useful in determining various boundary passings etc.

[John Diel]

I don't see why you couldn't run a packet transmitter during a severe event. I think Columbia Weather Inc. Has one that will interface well enough to do this www.columbiaweather.com (http://www.columbiaweather.com) but I couldn't tell you for sure. Though their systems are a little pricey for me, they appear to be pretty nice. They even have it thought out for vehicle mounting.

But as far as HAM Packet Transmissions, I don't see why you couldn't. I don't know enough about that area to give a good answer, but I would bet it can be done.

[Greg Stumpf]

Originally posted by John Diel
Looking at the Project Vortex stuff, they ... said they solved the issue of wind speed measurements while driving, but they didn't say how. I'm betting it was done post chase using the GPS info and vehicle speed rates in some formula.

GPS was used to subtract the vehicle motion vector from the measured wind in real-time. It is the same concept that R. J. Evans uses in his set-up, while loading up live data to the Web.

However, it was determined that the MMs measured wind best, while "in motion", if the vehicle speed was 40 mph or less, with very little velocity and angular acceleration. We exercised the "smooth, straight, and steady" driving technique when we were taking measurements "in transect" across dry lines or RFD gust fronts, etc.


greg

[Greg Stumpf]

Originally posted by David Drummond
...do you guys have ability to see APRS up there? I know some SKYWARN groups use it and if I remember right you can hook APRS up to a wxstation like a mesonet and broadcast that out with it.

Some of the WFOs use APRS to track spotters and grab their wx data. I'm not up-to-date on what the current NSSL technology is for broadcasting vehicle location and mobile mesonet data live to the Field Coordinator (FC) - I'm guessing a combo of satellite and/or 2-meter packet transmission. I know that the FC can see the location and wx of all vehicles overlaid on radar data (WSR-88D, SMART-R, etc).

Perhaps Scharfenberg knows more...?


greg

[John Diel]

Hi Greg,

It's a darn good thing I don't bet on the ponies. :D
I should have known there would be a real-time solution to that issue. I didn't think they would have had it though in that time frame. Makes sense though, if the MM could transmit the data, then the host computer could make the calculation and display it in real-time.

Thanks for the update. I rather doubt that I will ever get that technical in my area of chasing though. I figure I'm updated enough with a GPS and radio!

John

[Greg Stumpf]

Originally posted by John Diel
I should have known there would be a real-time solution to that issue. I didn't think they would have had it though in that time frame. Makes sense though, if the MM could transmit the data, then the host computer could make the calculation and display it in real-time.

Actually, the GPS vehicle motion subtraction is a rather simple algorithm, and that is done on the fly on the MM laptops. These data are available live inside each vehicle. Then, wx and location data are uploaded to server.


greg

[Kevin Scharfenberg]

Originally posted by Greg Stumpf+--><div class='quotetop'>QUOTE(Greg Stumpf)</div><!--QuoteBegin-David Drummond
...do you guys have ability to see APRS up there? I know some SKYWARN groups use it and if I remember right you can hook APRS up to a wxstation like a mesonet and broadcast that out with it.

Some of the WFOs use APRS to track spotters and grab their wx data. I'm not up-to-date on what the current NSSL technology is for broadcasting vehicle location and mobile mesonet data live to the Field Coordinator (FC) - I'm guessing a combo of satellite and/or 2-meter packet transmission. I know that the FC can see the location and wx of all vehicles overlaid on radar data (WSR-88D, SMART-R, etc).

Perhaps Scharfenberg knows more...?[/b]

I think most of the mobile teams these days are using home grown software for packet transfer over 2 meter, but I don't have any of the details.

[Joey Ketcham]

Just got my Oregon Scientific WM-918 weather station in today along with the software package that'll be on my laptop to continuously record and archieve the weather data.

I'll probably work on finishing my mobile mesonet up this weekend, I'm still unsure about the placement of my temp/humidity sensor. I originally thought about just mounting it towards the back back of the mobile mesonet on the metal bracket that is currently holding my old anemomenter or that or mount it on the backedge of the mast that is also holding the anemometer.

My only concern is that the high winds and rain will damage the sensor, will it or should it be ok?

[Chris Sokol]

It really does not matter where you mount the hydrometer so much as it matters that it is enclosed in a good radiation shield. You want zero actual water to reach the sensor.

[Joey Ketcham]

Thanks Chris, is there any special way to make the radiation shield or just as long as it's enclosed in one? Do you leave the ends opened or use some sort of vent?

[Chris Sokol]

I have the same style as the NSSL shield. It is quite large, but I did have it mounted on a passenger car previously.

http://www.kd5ili.com/images/truck5.JPG

http://www.kd5ili.com/images/truck4.JPG

http://www.kd5ili.com/images/truck3.JPG

Some of the parts needed include 2 drains mounted end to end (with the strainers removed), a cap, elbows and PVC pipe. I should have a detailed parts list on the receipt in my file cabinet. You also need a fan in the back to draw air through when stationary.

[Patrick Ware]

I am in the process of setting up for next season too and would appreciate it if you guys could post some schematics or links on details of how to construct a MM correctly.

I have started with a good Ham Radio with APRS and data link capabilities (Kenwood D700), traded in my sports car for a safer vehicle SUV, and would like to build a MM and get WXWorx ready for next season.

I really would like to hear again the pros & cons regarding WX stations (wireless vs. wired) and manufacturer.

I would also like it if someone could post the "essentials" necessary to equip a vehicle with to better enhance the chase.
Sometimes I believe that a handheld Kestrel 4000 may be just as helpful and useful to a beginner. The last thing I want to do is put up a bunch of equipment on my vehicle which says to everyone "Hey, look at me I'm a storm chaser". :roll:
I'm new to chasing but have been negotiating severe weather flying airliners for over 20 years. I want to study them from the ground. The downside is I can't runaway anymore in a straight line at over 500 KTS so safety and some experience with an experienced chaser would be appreciated.

Thanks in advance for the help and suggestions.

BTW, this forum has been great. I have really enjoyed reading all of your posts.

[David Sallee]

Originally posted by Patrick Ware
I am in the process of setting up for next season too and would appreciate it if you guys could post some schematics or links on details of how to construct a MM correctly.


Me too.... :wink:

[fplowman]

removed by poster to preserve the peace..

[Joey Ketcham]

Fplowman,

In response to what you said, the Kestrel is a nice unit to have but I think it’s better used for hikers and campers and whatnot. I own one, and I really don’t use it much because either it’s raining and I don’t want to get soaked or the inside of my car soaked to simply to a measurement.

One of the reasons I want one is because I wanted a system that will achieve the weather conditions in and around the storm, when I’m within viewing distances of a tornado simply put – I’m not going to want to sit there holding up a Kestrel to get measurements.

So once your chase is done you can go back and look at the achieved logs and use that info on many levels, who knows perhaps you, could even submit those logs to NSSL or local NWS for their purpose as well as share the data with the chase community.

Also something that Greg pointed out, the inspeed anemometer may not be correct due to the wind flow along the car – similar to the wind tunnel affect. Here’s a reprint of what Greg said:


The placement of your anemometer won't work. It is way too close to the vehicle chassis to get an accurate reading. You will be measuring air speed within the compressed airflow about the car - even if the vehicle is stationary (just think \"wind tunnel\"). In most situations, your measured wind speed will be an overestimate of the true wind.

NSSL engineers obtained information about the windflow about the vehicles that they mounted the mobile mesonets on. They found that the wind equipment had to be mounted pretty far away from the chassis in order to be effectively out of the vehicle airflow envelope. In later designs, this was about 3 feet high and 2 feet forward of the top side of the windshield.


So if the same applies to the inspeed, wind speed readings will not be accurate. So that's why chasers have the design that they do is to get the anemometer out of that wind flow for a accurate reading.

[fplowman]

Your right in many aspects Joey,

I was just replying to Pat as he said exactly what i was thinking when i followed your thread since its inception..
Again i didnt want to poke fun.. I was just playing somewhat of devils advocate.. Maybe someday i will see a need for a mobile Mesonet.. Otherwise.. The temperature barometric pressure and all that is recordeed and available through your internet apps for the area in my deduction.. Rain dont really bother me as a chaser.. goes with the territory and If theres a tornado?/ ill be busy punching or filming :D I would honestly like to find a need for one cause they are neato.. Jut not practical or helpful i believe for me at this time..
My 2cents.. No offense joey :wink:

[Dan Robinson]

I have an Inspeed mounted on PVC extending two feet higher than my truck's cab and six inches more out to the right. On calm days the readout is within +-2 MPH of my speedometer when I'm moving. When stationary, it has almost always been right on with the NWS locally observed windspeed.

Like Joey mentioned, it is beneficial to be able to get readings without standing outside in rain or lightning or otherwise diverting your attention from other tasks such as videography. Plus, the readout has maximum speed memory so you can catch the highest gust without having to hold an instrument for the duration of an event.

Some photos of my setup are on their site (I'm not paid by them to plug their product, it has just worked well for me).

I have had my anemometer mounted since October of last year, and it had seen about 25,000 miles of use, 12,000 of those Plains chasing this year. It finally developed a crack in the rotor after recording a 114MPH gust in Geary, OK on 5/29 and obviously didn't work right since. It finally broke off on I-64 near Jasper, Indiana on the way home from my last Plains chase trip. I will definately get a replacement rotor, I really am surprised at how long it held up considering what it has been through.

[Chris Sokol]

In reply to fplowman:

One of the many things that I have learned after 21 years of chasing is that the last thing that I would ever want to do is try to take accurate readings (or any type of readings, for that matter) in the core of a severe thunderstorm by sticking my hand out the window and trying to read the display of a handheld unit. Not to mention that the handheld units are very limited in comparison to full weather stations.

There is absolutely no reason to start this BS again...chase with as much or as little gear as you want, and leave everybody else the hell alone. It is none of anybody's business what any chaser either uses or equips their vehicle with. End of discussion.

You asked why would you "want to put that bohemoth" on your car. Well, the answer is extremely simple...if you do not want to, then don't. Nobody has told you that you need one, or that you have to have one. And you are also right about it being a hobby. And as with any hobby, different people are interested in different aspects of the hobby.

So in closing...you use what you want, I will use what I want, and have a nice day.

[fplowman]

wooooah.. pissed someone off not my intention... im new here and I had no idea this was a touchy subject..

On a lighter note I have an indian weather rock it suspends from a tripod.. It is wet when it rains and it rocks and blows with the wind when its windy.. it warms when its hot and is very cool to the touch in the cool air.. i might place one on my vehicle..

i didnt imply to drive down the road with my arm out the window and a $200 kestral.. Im on the storm at that time and i thought this mesonet tool was to help intercept?? Im unsure.. Sorry i pissed you off.. i thought i was being nice.. and i prefaced it with that.. i guess i am somewhat cantankerous.. oh and the moderator to the board just ripped my ass.. so my day is screwed up already.. 12:03 am here.. so much for the wishes of a nice day.. :?

[fplowman]

Chris.. i did go back and read what it is that i said that pissed you off.. i can appreciate i guess that someone would of taken that as mean spirited .. i didnt mean it that way though.. my appologies

Just went to your website and seen you sell weather units.. no wonder i pissed you off :D no harm dude..

[John Diel]

Now, now, let's all play nice here.

Back to the real question, does anyone have a set of plans or series of photos showing the actual construction of the aspirated shield? I've seen most of the photos before, but it's doesn't' tell me a lot other than it's a PVC tube with a cap on one end.

BTW: I've got a Davis Weather Wizards III on the way and like Joey, I would appreciate any good advice or help in getting the construction out of the way. You folks have the expertise and know what works and what doesn't. We can only benefit frmo that experience.

John

[Sheila_Ward]

Joey, have you looked at this?

http://www.weathervine.com/video/wxlab3.html

Chris Collura has designed a very nice, portable setup.

[Joey Ketcham]

Joey, have you looked at this?

http://www.weathervine.com/video/wxlab3.html

Chris Collura has designed a very nice, portable setup.

Yeah I did see that actually, also saw a video Chris has on his site too featuring it. Great design! My biggest challenege now is designing a shielf for my baraometer.

[John Diel]

Joey,

Just curious here. Why did you choose OSI over Davis on your station choice? Price? Features? Looks?

John

[Joey Ketcham]

Joey,

Just curious here. Why did you choose OSI over Davis on your station choice? Price? Features? Looks?

John

No reason really, I've heard good things about both Davis and OSI so I just picked up the OSI. Price was reasonable on it.

[John Diel]

Joey, Haven't heard from you about your project. I'm really curious to see how you set this up.

Since I will be using a Davis Weather Wizard III (temp and wind speed) with the possibility of moving to a Davis Weather Monitor II (Temp, wind speed, humidity and dewpoint) later on, I've decided to keep it pretty basic.

The sensor mast will be 4 feet tall. Below is a quick schematic of what I hope to see. All wires will be internal to the piping. I haven't decided on aluminum (smaller diameter and sturdy? but hard to fix when bashed by trees) or PVC (larger diameter for strength, but more wind resistance. Priced right, but really ugly).

I's certainly appreciate your's and anyone else, comments or suggestions on this design.

John Diel


http://www.pbase.com/image/30689720http://image.pbase.com/u47/okie34/large/30689720.sensor.jpg

[Joey Ketcham]

Hey John, I should be finishing it up shortly... I got my weather station and well.. had to do it. Mysteriously enough, the weather station got mounted on top of my house on the roof.... :D so I'm gonng order another one shortly to be used for my mesonet.

[Joey Ketcham]

Oh, in regards to the weather station since I mounted it we've had rain but the rain guage on it doesn't appear to be working as my weather station just continuously displays 0.00".. connection is good and I have it on leveled ground.. I even poured water into it and still never measured.

Any ideas?

[John Diel]

Since I've never seen the OSI stuff up close, I would venture a guess it's a bad transmitter. Especially if it's wireless. Here's OSI's trouble shooting page. I's give those a try, then call them if they do't work.

http://www2.oregonscientific.com/service/t.../detail.asp?c=2 (http://www2.oregonscientific.com/service/troubleshooting/detail.asp?c=2)

Still haven't seen any diagrams for an aspirated radiation shield? You would think it would be easy anough, but with the PVC pipe I see most folks using, I'm not quite sure how it all goes together.

Anyone out there listening? Please?? :)

John

[Joey Ketcham]

Actually I got the wired version, the OSI WM918 Weather Station but I'm thinking that when I get the one for my mesonet, I'm thinking about going wireless.. the cables are really long and would be a hassle in my opinion... but we'll see.

I have yet to construct a radiation shield, seems like a simple idea but just trying to come up with a way to make a good one with a good airflow through it.

[Patrick Ware]

My mobile mesonet just arrived today. It's already hooked up and ready to go. :wink:
Just seemed too expensive and too labor intensive to go the other way.

http://homepage1.nifty.com/NERUCO/Kestrel4000specification.files/image008.jpg

[John Diel]

Well, Patrick, I doubt you would have used that a whole lot last night in the areas where I was. I wasn't rolling down windows at all. In fact, I was trying to roll them up tighter!

Sorry man, I just can't see sticking my hand out the window with hail falling or heavy lightning in the vicinity. I'd rather let Davis do that for me.

John

[Joey Ketcham]

Perhaps when you get struck by lightning because your hand is sticking out of the window, then you'll change your mind about mobile mesonets on top of vehicles.

I just read that story recently about the storm chaser from Independence KS that was hit by lightning just simply by hanging his arm out of his window.

I would rather have the vehicle mounted mesonet rather than risking being hit by lightning because my arms is sticking out the window.

[Patrick Ware]

Just out of curiosity, why would someone be more susceptible to a lightning strike hanging their arm out the window while sitting inside a vehicle vs lightning hitting the highest obstacle on the vehicle (ie:a MM)and following the wiring into the vehicle?

I was under the impression that first, lightning usually hits the highest obstacle in the area, and second, inside a vehicle you are insulated from ground by four rubber tires.

I am not saying that this hasn't happened, but it would seem that just sitting in a vehicle in a lightning storm, with or without a MM, can be perilous.

How is your design coming?
You going to post some pictures?

[Joey Ketcham]

Patrick,

I'm not saying one would be more at risk by hanging their arm out of the car, but if your arm is hanging out of the car and your car is hit by lightning then you will sustain severe injuries. As far as the mobile mesonet, that's why you use wireless weather station so you don't have no wires running into the car. So that argument is invalid.

If you're inside your vehicle, no arms hanging out, and the lightning strikes your mesonet it'll travel around you via the shell of the vehicle and you should be fine. But even then, the mesonet is made out of PVC Pipe so it's not that great of a conductor to begin with.

So again, I would rather a mesonet get hit by lightning than having my arm hanging out and lightning hit the car.

I'm waiting to get my wireless station and then I should be near completion.

Once done, I'll get some pics uploaded.

[John Diel]

As far as lightning strikes go, the lightning will usually go the hight charged thing around the charged area of the ground. Most often this is the highest object in the vicinity. A tree, power pole, house, etc. Vehicles are not usually the thing struck. Even those running a 50 Watt HAM radio. Mostly because the vehicle is generally in motion, and it usually is not the highest grounded object. That's not to say it doesn't happen! We have a gentleman right here on this board that got a good jolt, most likely from a near strike. We've seen the viseo of the moving car getting zapped right on the hood. We've all heard of the photographer that got a good jolt from a near strike via his tripod. We know it's a possiblity. The odds are in our favor, but we definately increase those odds of getting hit, by purposely being in the area.

The biggest reason I've built an MM, is to be able to give reasonably accurate reports to a listening base of poeple in our radio coverage area. They wasnt to know what's coming at them and I don't guestimate wind speeds very well in the dark (not in the daylight either!). The harvest is pretty much over in this part of the state, but there are a lot of farmers that want to know what's happening in their fields. Most of them will be out on the tractor or combine and listening to the radio. Accurate reports will help him know how long he has before he has to pack it in or if he'll have a field left after a hail storm. There's another reason. I don't relish the idea of sticking my hand out and getting hit by a large hailstone. I really don't like sticking it out and getting it all soaked (plus the interior of my truck) and then trying to drive. It just makes more sense to have all that outside with me as comfy as possible inside. :D

All that aside, I finally got it all put together, though it will most likely remain a work in progress. What I ended up doing, was using a photography monopod I had laying around and mounted that to the back of the camper shell. That allows me to telescope the entire sensor array up about 5 feet above the top of the vehicle and also keeps me from bashing trees around the house. The down side is the monopod is permanently mounted. not a major issue, but one I would have liked to avoid. I'll put up photos in a day or so. I'm hoping NC OK get a little weather tomorrow (monday) so I can actually give this things a decent run through.

I also will be replacing the weather wizard III with a weather monitor II. That will give me the humidity and dewpoint reading missing from the wizard.

Later folks!

John

[Joey Ketcham]

Kinda along the same line as you John, something I did when I mounted my weather station on top of my house.... I do a lot of photography and I had an extra light tripod sitting around, one of the heavy duty all metal ones that extends to about 7 or so foot high... worked out well for my weather station.

I took it and mounted my anemometer on it, then mounted the tripod onto the top of my house to a pole by taking the tripod legs off and then once it was bolted and mounted I just extended it up into place and is study as can be.!

[Chris Sokol]

Joey...did you remove the cover off the rain gauge and remove the ties on the tipping mechanism? Davis haz zip ties on theirs when you receive them to keep it from being damaged during shipping. OSI may do the same...it sounds like the problem that you are having.

[John Diel]

Well, it's not the best picture in town, but here is the "Ugly Green Truck"

http://www.pbase.com/image/31035542

The antennas on the roof are: Scanner, 2M Ham, Cell Phone. The mast in back is telescoping another 3 feet up and carried the Davis Wind Direction and Speed meters.

I got to test the mast in some pretty serious wind this morning. I recorded gusts up to 63 mph while in the Tonkawa area. Moving at 70 mph with 15 to 25 mph winds was also a good test (Down I-35 monday afternoon). The issue I had was the sensor itself coming loose and starting to twist. This was especially true with the 18 wheelers flying by.

The mast is simply held in by 6 inch cable bolts and mounted to the camper shell. This mount in reinforced by the shell braces and was really very stable in heavy winds.

John

[Joey Ketcham]

Hey Chris, I got the rain gauge to work.. I felt like a tard' too. Guess that's what I get for not reading direction :oops: then I would of seen that there is tape on the inside holding down the tipping device inside. It now works.

John,

I like your setup, it's nice and simple and gets the job done. If only I had a truck now... once I can get my wireless weather station I'll go back to working on mine.

[Dan Starker]

Hey John,
Was reading this old post as im kinda new to this forum and as I was reading I knew the answer because I had the same thing happen to me.
So I kept reading the posts to see if you figured it out and on the last post you finally did. lol good job glad ya got it. I know i felt dumb when i figured it out . :D
Reading this thread to see if you figured it out was like reading a suspense thriller book and at the end he gets the girl.

Once again great work and ty for all your info on this forum, you and others have been very helpful plus its good to see im not alone in the challenges we all face in getting the right equipment for the art we love so much.

[Mike Sharp]

Hi,
Regarding APRS, check out www.byronics.com they to a WXversion of their Tiny Track3 and links to forums dedicated to APRS
No connections other than satisfied customer .
you can also find out which weather stations are supported.
Just one thing at present Ui-View which is a brilliant piece of APRS software is not available as a full blown version because its author is in Hospital full details on that forum.


Finally to the moderators sorry if this is borderline just trying to help with what works over here .

[Mike Sharp]

websit adress wrong should be [www.byonics.com][/url]

[John Diel]

Well, it's finally done. I finished up the radiation shield today. Now I don't have photos just yet (next couple of days?) but here the list:

1 - 2 foot section of 2" PVC Pipe $1.39
1 - PVC Pipe connector $.79
1 - 45 degree PVC Elbow $.79
1 - 2 1/2" PVC Cap
1- Glue $3.00
1 - 12V DC fan (Radio Shack) $13.00

I listed a 2 foot section of pipe as that was the smallest I could get it in. Any way, I cut a 7 inch section off this to be the body. 45Degree elbow is on the bottom pointed away from the vehicle. The connector fits over the top pipe and has holes drilled in it for ventilation and wire leads. The Davis Thermometer lead is no larger than standard phone line, the power leads for the fan are tiny.

As far as the temp sensor touching the sides? I found that it really doesn't make a lot of different with the Davis sensor. I ran up and down the road with it touching and with it weighted down with fishing weights (not touching the sensor) and found no difference in the temp.

The Cap is just large enough to let air move around with the benefit of the fan. Cuts were made to 1/2 inch to accomodate the fan, which if the cuts are about 1/8 inch wide, they will hold the fan tightly.

I also have two screws on either side of the cap as I didn't trust my gluing job. The whole thing is about 9 inches long and it secured with wire ties (poor man's bungie) to the sensor mast.

Since I doubt that I will be getting the temp/humidity sensor anytime soon, I'll stick with this and the sling psychrometer (yes, I still use one). Anyway, after talking to Davis Support, there isn't a really good way of mounting the sensor without their radiation shield. I really don't think I wat to pay out $400 bucks when what I have does a reasonable job of things.

John

[Jack Beven]

Originally posted by Greg Stumpf+--><div class='quotetop'>QUOTE(Greg Stumpf)</div><!--QuoteBegin-jketcham
Been working on my mobile mesonet today, so far here's what I've gotten so far.

The placement of your anemometer won't work. It is way too close to the vehicle chassis to get an accurate reading. You will be measuring air speed within the compressed airflow about the car - even if the vehicle is stationary (just think "wind tunnel"). In most situations, your measured wind speed will be an overestimate of the true wind.

NSSL engineers obtained information about the windflow about the vehicles that they mounted the mobile mesonets on. They found that the wind equipment had to be mounted pretty far away from the chassis in order to be effectively out of the vehicle airflow envelope. In later designs, this was about 3 feet high and 2 feet forward of the top side of the windshield.[/b]

Greg, is there anything published on how far away from the chassis the anemometer need to be? We've had several reports from such units from Hurricane Alex (inlcuding a gust of 120 mph), and I got one from Hurricane Claudette last year that looked like a significant overestimate.
I'd like to tap some of your and NSSL's expertise on how to evaluate these reports.

Jack Beven
jbeven@mindspring.com

[John Diel]

here's the updates I promised


http://www.pbase.com/image/32326722
http://www.pbase.com/image/32326734
http://www.pbase.com/image/32326772
http://www.pbase.com/image/32326776
http://www.pbase.com/image/32326778
http://www.pbase.com/image/32326784

I'll be building another one pretty soon (hopefully a little bit cleaner) and I'll get photos of the contruction process

(edited to remove bad hotlinked images)

[Gaetan Cormier]

Originally posted by John Diel
here's the updates I promised


http://www.pbase.com/image/32326722
http://www.pbase.com/image/32326734
http://www.pbase.com/image/32326772
http://www.pbase.com/image/32326776
http://www.pbase.com/image/32326778
http://www.pbase.com/image/32326784

I'll be building another one pretty soon (hopefully a little bit cleaner) and I'll get photos of the contruction process

(edited to remove bad hotlinked images)

Good work John,

In your shield, how is your sensor placed and also the fan... is the fan on top or underneath your sensor?

Thanks

[John Diel]

Hi Gaetan!

The fan is way up in the top of the tube (over the sensor). The sensor is simply hanging (actually a one loop coil) inside the tube.

The Davis standard Temp Sensor is no bigger than a thick telephone cord. I did some experimenting (used toothpicks to keep the sensor reasonably centered in the tube) and came to the conclusion that the actual temperature reading has a +/- 1 degree F variance if centered or not. I was using the Ponca City Airport reports as a guide line, as well as taking my own readings locally, and then used the average of the two as the guide. The fan is key to the whole affair to keep the air moving over the sensor. Otherwise it will slowly build up. My expereince showed about 5 to 8 degrees over the average readings (same as above), depending on wind speed and direction.

Here is a quick schematic I did. Not the best, but it will give you an idea of what the inside looks like:

http://www.pbase.com/image/32365403

Hope this helps!

[John Erwin]

John;

First of all, thank you for posting the details of your work. I've been waiting (like a lot of people it seems) to see a schematic of the NSSL design, but your design seems to look very sound as well.

Some questions; did you notice much variation in temperature between moving and when stopped? How about when the fan is used/not used when stopped. I ask about the fan because I'm aware of the need to move air across the probe...but I'm wondering how much air is needed before it begins to affect the temp by a chilling effect.

Thanks once again for your hard work!

[John Diel]

Hi John.

Again, I compared my results with the Airport (reports "Official" Temperature to NWS) and my own local reading using a sling psychometer and another Weather Wizard III and then using the average as the guide.

The fan keeps enough air moving across the sensor to to keep the temp within 2 degrees of the average. The vehicle moving also kept the 2 degree variation.

So, for the purposes I will be using it for, I would say it's well within acceptable limits. I know there's a formula someplace that will give you the volume of air needed to keep things right, but the little bity fan is just enough to keep the column clear with ambient air. Moving down the road at 70 mph, of course, overpowers the fan (I simply turn it off rather than burn out the motor) but there was no significant differences unless the vehicle was stopped, the fan wasn't running and there was little air movement (5 mph or less wind). Then I saw the temps rise about 5 to 8 degrees from the compared average.

Now if Davis only made a humidity sensor small enough to fit that!

John

[Gaetan Cormier]

Hi Gaetan!

The fan is way up in the top of the tube (over the sensor). The sensor is simply hanging (actually a one loop coil) inside the tube.
...........
Here is a quick schematic I did. Not the best, but it will give you an idea of what the inside looks like:

http://www.pbase.com/image/32365403

Hope this helps!

John!

Thanks alot for sharing the schematics with us.. I will definetely apply this to my mobile mesonet too, cause the way I'm mounted right now, I get wrong readings when I'm stationnary.... Well, I guess I will be totally ready and geared for next year.. since the season here is getting close to an end.