My setup; what do you think?

23m (75 feet) AGL…

Does anybody here outgust the local airport using the normal DVP2 Anenometer?
(without using offsets naturaly)

Cheers

is the setup wired or wireless ?

if wired, do you have lightning protection ? 8O

If wireless… how do you change the batteries? #-o

Dwain

no batteries, its just the davsi VP anenometer, wired

if foggy gets a direct hit by lightning, he will die happy, at least
:lol:

looking good foggy!

Now that looks fine… I wonder if my wife would let me do that in the name of science? :glasses5: ( dear there is a man from Chicago by the name of Rocko who wants to discuss your wanting to put the thing on the roof again.)

Nice work! Mine is on a tower about 40 feet up and 12 feet or so above the peak of my roof. With no mature trees to obstruct the flow my readings usually match our local airport but are almost always higher than the nearby CWOP stations. That’s most likely because most residential areas don’t have the best exposure for wind and not everyone can have their anemometer as the standard 10m height. My guess is that you may indeed outgust the competition (sounds like a commercial).

[quote author=cyclone link=topic=12459.msg95139#msg95139 date=1132486054]
is the setup wired or wireless ?

if wired, do you have lightning protection ?

kind of like the old joke “where does a 600 pound gorilla sleep?” any where it wants to.

You should ground the metal pole to be on the safe side.

But does grounding the pole make it more likely to be hit?

I don’t think so… Since it is the highest object in the area, a proper grounding would be of a benefit. Notice “proper” using the right wire, stand offs etc.

I suppose he could try it out without, the cost of a new anenometer is about 125 US and the console a bit more and assuming that if it is connected to his computer, the console fries first…

I don’t know… My unit is grounded

You mean that thick copper strapping about 2 inches wide by half an inch thick? I bet that’s expensive #-o

I’ve done some research on lightning last month:

Grounding does NOT attract lightning.
the earth cable doesn’t have to be that thick, you will get away with 4mm2, because lightning only last a fraction of a second.

Oh also, do not have multiply earth stakes, if you must have multiple earth stakes, they must be bonded together.

My lightning theory isn’t recent, but I was always told that a grounded pointy spike acted as a focal point for lightning. If I remember correctly the theory was something about it removing localised charge in the atmosphere (due to the grounding) which generated a positive field around the grounded spike. Opposites attract so the highly negatively charged lightning strike preferred a route with a positive charge. Clearly a grounded spike isn’t going to attract lightning from miles away, but I would have thought that if a strike was going to occur within 50-100 ft of a grounded spike the spike effect may have some effect.

I’m also amazed that a 4mm² cable could dissipate a strike. A quick Google suggests that people supplying lightning conductor cable sell cables that are around 1/2 inch diameter or greater. These are multi-core, but if solid they’d have a cross section of over 100mm² or 25 times greater than your suggestion. Ther suggestion is that the weight of the cable is more important than it’s diameter…figures of around 200lb/1000ft are mentioned and I can’t see a 4mm² cable reaching that kind of weight.

WARNING: I am not an expert, so anyone trying to do this for real should consult an expert!

maybe its a case of the bigger the conductor, the bigger the strike you will encourage, too?
(i.e as it could be just a very small hair filament spark thats all is needed to do damage (there was a posting on this forum about exactly thats what happened, from a nearby strike)

Found this on the National Lightning Safety Insitute. They aren’t selling anything so may be more inclined not to strech the truth.

Lightning Rods
In Franklin’s day, lightning rods conducted current away from buildings to earth. Lightning rods, now known as air terminals, are believed to send Streamers upward at varying distances and times according to shape, height and other factors. Different designs of air terminals may be employed according to different protection requirements. For example, the utility industry prefers overhead shielding wires for electrical substations. In some cases, no use whatsoever of air terminals is appropriate (example: munitions bunkers). Air terminals do not provide for safety to modern electronics within structures.

Air terminal design may alter Streamer behavior. In equivalent e-fields, a blunt pointed rod is seen to behave differently than a sharp pointed rod. Faraday Cage and overhead shield designs produce yet other effects. Air terminal design and performance is a controversial and unresolved issue. Commercial claims of the “elimination” of lightning deserve a skeptical reception. Further research and testing is on-going in order to understand more fully the behavior of various air terminals.

–Dave

I suppose there are a number of things to consider…the main strike, a side-strike and induced voltages from a nearby strike. I know from personal experience that induced voltages can fry hard disk controller cards and modems. It happened to me 10-12 years ago from a strike which blew a hole in the roof of a shed 4 doors away.

If air terminals aren’t suitable for munitions stores, then it would appear that they must have some effect!

I wouldn’t bother grounding it. Surely if it gets hit by lightning then you’re anemometer is going to be damaged regardless of whether the pole is grounded or not. Unless I’m missing something? Also if its grounded wouldn’t it make it an easier path for lightning to go to ground than if it wasn’t, seeing as electricity takes the easiest route to ground.

Surely if it gets hit by lightning then you're anemometer is going to be damaged regardless of whether the pole is grounded or not

Thats possible to some degree, especially from the static point of view. But still the static or lightning (if its a direct hit) will follow the path of least resistance. So the theory is that in both cases that is down your pole/mast to earth, rather than via your gear to earth.

the earth cable doesn't have to be that thick, you will get away with 4mm2, because lightning only last a fraction of a second

That may prevent static buildups but lighting strikes can deliver hundreds of amps in a fraction of a second. A thin grounding cable will vaporise in far shorter time than some strikes will last for, leaving the lightning to then find the next least resistive path, probably your equipment. Have a look at a professional installatin on a comms tower. The lightning strap will be solid metal a couple of inches wide (or more) and 1/4 inch thick. And it normally runs all the way from the rod at the top of the tower to the ground to make sure it is the path of least resistance.

The best way overall (IMHO) is to have a totally seperate pole, higher than your equipment, acting solely as a lightning conductor. But that is often not practical (or affordable). We each need to do our own cost analysis and determine if its worth it.

going to find out more about this