Anemometer Mast Earthing

[glynh]

Hi all,

I will be installing my anemometer this week (hopefully, depending on the weather ) up on my chimney using a 2m ally mast. Is it recommended to get the mast earthed incase of lightning strikes (our nextdoor neighbours tree got struck several years ago) and if so what do I need? Does anyone else have their mast earthed?

I am using a wireless anemometer so there is no wired connection indoors.

Hopefully, once this is in place I can then get my data up on the web.

Cheers

Glyn

[optrex]

Mine isn't earthed for lightning and its a 5m mast, so I would be interested in hearing the consesus of opinion here. I would imagine it would be quite expensive to do.

[johnholmes]

neither is mine, its about 18ft high from the ground

[stormuk]

Any masts at this location are earthed, but then they also have Transmitter/receiver antennae on them.

Easiest way to do it, Buy an Earth rod off E~~~ or builders merchants I think I got mine from Wickes, Jubilee Clamp size of Mast and then run from the earth clamp to the mast Earth cable available from your local Electrical wholesalers - Must be the heavyduty cable, I use 2.5mm solid copper.Use the sleeved stuff.

The earth rod has a screw fitting on the top and the other end just tuck the wire under the Jubilee Clip and tighten.

But I also have lightning arrestors in the coaxial feed for the Radio stuff.Linked in the same way.I only have one metal mast ,the other two are Fiberglass so are insulated anyway(Old windsurfers have their uses)

Don't think there would be a problem with wireless units however It is something I would do on on a wired unit.

Edited January 2, 2006 by stormuk

[Cloudburst]

This is a good question, my mast goes up to about out 31ft, it is attached to my roof and is about half a meter highter than everything else including the near by houses and their chimneys, this is because i wanted good reliable readings. Anyway, i have not yet earthed it, but i should as it is likely to get hit, being on an aluminium 7ft pole, and being higher than all the other houses.

But to earth it all you need to do is attach some copper wire and make a spike that is higher than your pole, so the lightning strikes that first. Then route is safely to earth, basically wire it up to the ground, making sure it satys well away from anything that could get damaged, and you should be O.K then.

[Mondy]

I am using a wireless anemometer so there is no wired connection indoors.

You've answered your own question really I wouldn't bother earthing it - full stop! None of my aerials are earthed (should be, but aren't)! Highest one is over 40ft and that has had numerous lightning storms flashing at it over the years...

If you want to be on the safe side, a lightning arrestor would be ideal

[optrex]

Must be the heavyduty cable, I use 2.5mm solid copper.Use the sleeved stuff.

The earth rod has a screw fitting on the top and the other end just tuck the wire under the Jubilee Clip and tighten.

Just a quick question storm: For lightning protection wouldn't 2.5mm cable melt ? I could understand its use for grounding an antenna but would have thought copper banding would have been required for lighning conduction. (like type seen on tall buildings, churches etc)

[frogesque]

First off I would check your household insurance policy, a pole or aeriel mounted on the chimney stack may be a get-out clause if not properly installed because they may claim you attracted the strike. You may also have public liability in the event of wind damage or other catastrophy.

Earthing for lightning is quite a complicated subject. A full hit can vaporise wood, metal, brick and concrete if it happens to be part of the shortest path to an electrical ground. An industrial chimney stack near here lost 3 foot of brickwork a few years ago due to lightning and the top had to be rebuilt - and that had lightning conductors!

The duration of a bolt is fairly short but votage and current are huge. It's not just enough to provide a wire (normally several heavy copper straps to different parts of the building) but they have to be connected to electrically conducting ground for the energy to disipate. All joints must be electrically sound too. Lightning conductors attract lightning (TS watchers note!) but are designed to take a strike rather than it going through other unprotected parts of the buiding.

Although it refers to a boat, the catamaran Lady Bounty there's quite a good article about lightning here

[Nabraxas]

I'm the same as Mondy on this one; I have a scanner aerial sitting around 40ft above the ground and it isn't earthed, if lightning was to strike it the worst that could happen is it blows the house up...

Right, I'm off to earth it <_<

[glynh]

@frogesque - My insurance policy was one of the things I was thinking about, in that like you said, the small print may hold some disclaimer about such equipment and it's installation. I will have to have a look, when I can be bothered to go up in the loft and get the policy down- although if we magically get struck by lightning in the meantime, it may come down of it's pwn accord.

@everyone - After I posted, it suddenly dawned on me that the majority of peeps have TV/Radio aerials on their roofs, so perhaps I am worrying a bit too much. We don't have an aerial as we are in direct sight of Emely Moor TV Mast but others on the street do. I notice though that a house a bit further up the hill has a lightning conductor on it - think it might be the health clinic so maybe their insurance requires it.

Anyway, thanks for the comments so far. I think I will look at my insurance policy to double check - but my gut feel makes me think I probably won't need to bother. It's probably low risk that lightning will strike it.

Glyn

[Meteorologica]

If you have an Oregon Scientific anemometer then it is a requirement that you earth it, they even have a tag on the end of the anemometer's arm just for this purpose. The anemometer is very susceptible to static buildup and it will simply stop working at some point needing a reset to get it going again if you don't earth it. This isn't lightning protection just a way to drain away any static charges it collects.

[glynh]

Tim,

Cheers for that. I'm off to B&Q today so I may as well get some earth bonding wire (like they use for plumbing etc) and earth it for this purpose.

Glyn

[Cloudburst]

Tim,

Cheers for that. I'm off to B&Q today so I may as well get some earth bonding wire (like they use for plumbing etc) and earth it for this purpose.

Glyn

Well i think i'll just ponder about it for a while longer, as if anythings going to attract the lightning, not far from my house is a full size Radio mast that rises above everything, and in the 15 years the t.v mast has been up and through all the t-storms its never got hit (Touch wood).

[glynh]

CloudBurst - thats my thinking really. I'm only gonna provide a simple earth bond so the static from the anemometer can dissipate easily, so I don't get any spurious readings or it stops working.

Probably will earth it to my outside security light housing.

[Osbourne One-Nil]

I've got a cabled VP2, and have had terrible problems with false anemometer readings because of static. I tried earthing it, but to no avail, and in the end I had to get an optical isolator, which works perfectly. I know it's nothing to do with lightning, but it's worth remembering.

[glynh]

Hi OON,

Could you describe where such a device would be placed and how much it costs. I've never heard of one of them before and Googling it returns some quite technical stuff.

As I haven't erected the anemometer yet, I don't know what probs may be lurking there, but I'll earth it all the same if only to try and alleviate any static probs.

Anyway got me stuff sorted, hired the ladders and Thursday, hopefully, should be the big day (well in my eyes anyway ).

Cheers

Glyn

Edited January 3, 2006 by glynh

[Mondy]

Tbh, Glyn - the higher erected the better. Away from nearby TV aerials, other cables, close-by houses. The static OON has/had is probably man-made ie, something within his house (or more likely his neighbours house) causing the problem..DVD player, TV on standby, Sat dish, neon light bulbs..they all contribute to noise/static levels.

The only static level noise you should have is when a thunderstorm is in the vicinity! This again goes full-circle regarding your original question..

Edited January 3, 2006 by Mondy the clumsy

[Cloudburst]

Tbh, Glyn - the higher erected the better. Away from nearby TV aerials, other cables, close-by houses. The static OON has/had is probably man-made ie, something within his house (or more likely his neighbours house) causing the problem..DVD player, TV on standby, Sat dish, neon light bulbs..they all contribute to noise/static levels.

The only static level noise you should have is when a thunderstorm is in the vicinity! This again goes full-circle regarding your original question..

My wireless anemometer works great and i have had no problems or flase readings what so ever. Its located not far from my TV aerial but works fine, i guess its becuase it is completely wireless so there is no medium to which can interfer with the signal.

As most other people have said ( if it is cabled) then it may be good practice to earth it to release static build up as apposed to a lightning strike. But to be fair if your sensor gets a direct hit its days are over even if it has a conductor.

Edited January 3, 2006 by ¤CloudBurst¤

[Mondy]

i guess its becuase it is completely wireless so there is no medium to which can interfer with the signal.

Out of interest what is the frequency range of a wireless anemometer? Considering a Tv aerial is tuned to approx 60-80Mhz, i'm presuming a wireless anemometer frequency is very much higher? That inturn shouldn't effect the received wireless signal. Which is why you have no probs

It's stuff like PC internal clocks, DVD players, mains-borne interference that can really cause hassle - within close proximity of the anemometer set up..i found it fascinating when i learned about EMC, during my radio exams, but have since forgotten quite a bit :o

EMC

[Cloudburst]

Out of interest what is the frequency range of a wireless anemometer? Considering a Tv aerial is tuned to approx 60-80Mhz, i'm presuming a wireless anemometer frequency is very much higher? :o That inturn shouldn't effect the received wireless signal. Which is why you have no probs

It's stuff like PC internal clocks, DVD players, mains-borne interference that can really cause hassle - within close proximity of the anemometer set up..i found it fascinating when i learned about EMC, during my radio exams, but have since forgotten quite a bit :o

EMC

Yes, my Sensors all work at 433mhz, the VP2 wireless is even higher than that, so at those frequencies very little can interfere with them. As for the rest everything works fine, but i must say that all the sensors are located a good distance from any devices like the ones you mentioned.

[glynh]

Well Mondy and CloudBurst, I have no TV aerial on my roof and neither do any of my neighbours. In fact the closest one is about 100ft away across the street. So hopefully I should have no problems.

I think the lightning conductor idea has gone now. If we get struck, I can't imagine that the anemometer would last anyway, regardless of if there was a proper conductor on it or not.

Just out of interest, has anyone extended the cable from their anemometer to the wireless solar unit (on a WMR928NX) and if so what did you use?

Seems to have provoked some discussion this thread.

Glyn

[Osbourne One-Nil]

Hi OON,

Could you describe where such a device would be placed and how much it costs. I've never heard of one of them before and Googling it returns some quite technical stuff.

As I haven't erected the anemometer yet, I don't know what probs may be lurking there, but I'll earth it all the same if only to try and alleviate any static probs.

Anyway got me stuff sorted, hired the ladders and Thursday, hopefully, should be the big day (well in my eyes anyway ).

Cheers

Glyn

Sorry Glyn, only just seen this.

The problem only affects cabled systems, and then only some of them. But, if you do have the problem (which soon becomes apparent) then the optical isolator I have fits between the USB cable and the computer, in effect breaking the direct connection between the two (it uses fibre optics). It's an expensive option (£150) but the only option, so wait an see if you have the problem first.

Since installing it, I've never had a problem...until today, when my anemometer is reading a permanant 0mph. I wish it wasn't 40ft up.

[glynh]

thx for the reply OON.

Well it is a relief of somesorts that it is only cabled systems that are affected (one less thing for me to worry about ) however until it is installed (hopefully this wed) I won't know. Fingers x'ed.

Glyn