My Mobile Mesonet

Just got mine up and running today!

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
 
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.!
 
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.
 
Not the best, but here it is

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
 
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.
 
Rain gauge

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.
 
APRS

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 .
 
Finally got it all built

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
 
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
[email protected]
 
Re: update w/ pix

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
 
Fan and Sensor

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!
 
temp shield

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!
 
Fan air movement

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
 
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