Mobile Mesonet Sensor Array

John Diel

Mar 25, 2004
North Central Oklahoma
Still waiting on Chris Sokol to post his plans on the Radiotion Sheild and array.

Anyone else want to chime in, I know I would certainly be appreciative!

shields up scotty

From pictures i have seen far away of this i am guesstimating the pip to be about a 3" diameter PVC with (2) 3" 90 degree angled corners. They ends seem to be attached to main pipe using screws or bolts not the pvc glue ,
I am assuming this is so u can get at the sensor inside, depending on where that is placed which i have no clue.

The cap on the front or top section has me confused abit only because most pictures i have seen, even those from the NSSL & project vortex dont show how they allow airflow into the pipe. I will assume they drill holes into the pvc but where and how many to allow enough airflow but keep moisture out as much as possible.

The other rumor i heard was some of these have fans inside to grab air in when vehicle is at a dead stop. Would like much feedback on this as I would like to know what power source or where these fans are placed if used at all.

Out of all the instruments I been learning about this simple device has my most attention and curiousity.

May I request to those that offer these answers, some closeup pics of each component I have mentioned and/or a diagram with measurements of ur design.

For those that have regular fan aspirated shields I would like a discussion to compare which works better for mobiles. Cause i notice some in my chasing group here use regular shields not the NSSL design. Ty all for any and all input on this you guys rock on here.
Airflow in shield

The Cap would have to go over some slots of some type allowing the air to flow through the pipe. I suspect an oversize cap is used then threaded with a couple of homemade adapters to accomodate the airflow. Again, this would work as long as you were moving forward and the rain coming from the front or sides of the shield. If the rain was coming from the rear of the shield and being wind driven, it would probably get in the shield. I don't know that there is a 100% solution to this issue.

Getting a 12 volt fan in the size needed, doesn't appear to be much of an issue either. I did a quick search on e-bay and came up with several low priced fans. With some modifications to the fan housing (square to round) I think they can be made to work out pretty well.

What I really have no good idea on is the actual mounting of the sensors inside the shield. I've thought about some type of spider web system (similar to those used on the secondary mirror in a telescope) or simply a small block of plastic mounted inside the tube. I assume the whole issue is to keep the sensor off the insides and centered as much as possible. Anyway, I would think that would be the way to get the best results.

It's also very possible, I'm over engineering the whole thing too!

One other issue. In looking at the Davis Intruments website, it appears that the humidity/Temperatire sensor is this great big square thing with a couple of protuberances. How in the world that would ever work with the system I'm looking at, is beyond me. Since I haven't seen one close up or taken one apart to find out what the actual sensors look like, the whole thing may be a moot point.

Those of you that use the Davis Humidity/Temperature sensors. speak up! What can you tell us? :D

I own a Davis temp/humidity probe & use their special radiation shield to optimize my readings when storm chasing. I'll see if I can upload a couple of pics soon, but basically I devised a way to mount my RM Young aerovane, Davis temp/hum. probe, & serial box converter/electronic compass on top of my Jeep Grand Cherokee by attaching the devices to the top of a standard 1-inch galvanized (rust-proof) metal pole. From my experience with this setup, I can say the white grill-like radiation shield Davis Instruments provides as an accessory to their standard temp/hum. probe works very well in giving me accurate readings on the Davis Monitor. Even under blazing hot sunlight, the radiation grill keeps the probe evenly cool with the surrounding environment while air flows fleely through the entire assembly.
The mount configuration is similar in design to those on NSSL's mobile mesonets, with two metal pipe crossbars going across the front & back of the roof & an upright pole attached to the center of the front bar, extending up just over 5-feet from the roof of the vehicle. Two additional pipes support the upright & are attached by a steel bolt drilled through all 3 poles. Of course, the supports (diagonal poles) are bolstered on the other end by the rear crossbar which, along with the front crossbar, is securely attached to the car by two Yakima clamps. Of course, the best thing about this assembly is no drilling required :p ! (Into the car, anyway)
I'll post some snapshots of this soon. Hope that helps u guys!
Grill versus NSSL "S" PVC Pole

Yes all this information is very helpful but pictures speak 1000 words in this situation :D lol.
The grill shield vs. the NSSL "S" shaped pole.
I know the NSSL pole has to be so high up to get out of the flow of the vehicle but does this apply to the grill shield as well.
Cause I have seen vehicles with the grill cover and its set close to the car for aerodynamic reasons obviously.
I guess what im asking for is the pros and cons of each when used in a mobile situation. And I look forward to all the picture and diagrams you can spit out . LOL
Been a busy year up here in Wisconsin so im trying to get something put together soon.
Thank you all for your inputs and help on this one, :D
Vehicle slipstream

The only thing that really needs to be out of the vehicle slipstream would be the Anemometer. That the only real piece that would be affected since it reports wind speed. Temperature and humidity should not be affected since it's still ambient air traveling over the sensors. The only reason I can think of to move it up some would be to keep it out of the vehicle spray from rain.

No matter where it goes (outside the vehicle) it's still going to be subject to birds, bugs and normal road grit. So far, mine has stood up to a few meadowlarks and come out the victor. Now hail? I've managed to stay out of the major stuff so far this year.
our O/S sensor is covered with a sideing corner. yep sounds dumb but it works fine +/- 2 deg.
Well, since I never heard from Chris (well I did, but he got busy), I've gone through a couple that were posted here. I first went with a scaled down version of the NSSL Sewer tube. It worked out pretty good, but my mounting solution left something to be desired. I now have a Viasla passive shield that, so far, has worked out very well.

Thanks for posting though, I would love to see a close up of your system and set up though. Any ideas would be welcome.