Topic: Erratic VP2 Anemometer

[Paul]

My previous anemometer died after 6+ years service so I purchased a replacement 6140 to use with my existing transmitter.

Due to its placement up on the roof I paid an Aerial fitter to help me install.
All seemed well.

Winds have been light so I didn't pay it much attention but I suspected something wasn't right.

Today is an unusually windy day here in the UK and things clearly aren't right with it, not getting anywhere near the readings I should.

So I observed it and it seems all over the place, it will spin seemingly normal for a couple of seconds then stop, sometimes even going 'backwards'.
The vane also seems to be spinning quite erratically.
When there is a sustained gust it will 'spin-up', not as high as it should be though, but wont sustain and readings will drop.

I notice that the mounting pole isn't quite vertical so that may have an effect.

Not sure what to do, don't really want to pay a load more money for someone to go up on the roof if I can't be guaranteed to fix it. Very disappointed.

Anyone have any thoughts?

[johnd]

Of course it's best if the pole is truly vertical but I doubt that slight deviations from vertical are going to make much difference.

There really isn't too much to go wrong with the speed sensing. Provided the cups are not grossly malformed (which I'm sure you would have noticed on installation) and are tight on the spindle then rotation of the cups is down to pure aerodynamics and the design of the 6410 cups is tried and tested, including careful wind tunnel calibration. I suppose it's possible that the bearing is faulty, but again you would probably have noticed on installation and any excess friction is unlikely to have developed in a relatively new anemometer.

My best guess would be that you're seeing genuine speeds as a result of the wind swirling and eddying around the roof structure (yours plus any other nearby houses, large trees etc). But that can obviously only be a guess without more detailed knowledge of the installation.

[Paul]

Thanks for the reply John.

Looking at it again and you could be right. It is mounted in a different place compared to the old one, slightly lower and directly north of the Aerial which is on another pole.

With the current southerlies that could definitely impact it. Lets see what happens when it swings around more to the west which should be impeded less.

[Mapantz]

Out of interest, how much did you have to pay the aerial person to do it? If you don't mind me asking.. I'm dithering whether or not, to stick mine up on my chimney .. It means having to buy a wireless transmitter (not sure how much they are)
I live in a house owned by a housing association, so the maintenance guys have roof ladders etc.. I was thinking of chucking them 20 quid to do it. I have a bracket that is ready to be screwed in, that will hold an 8' pole, so 4' would be above the chimney pots. The chimney itself is 11m up, it'd be a nightmare is something fails on the anemometer again.

[dalecoy]

So I observed it and it seems all over the place, it will spin seemingly normal for a couple of seconds then stop, sometimes even going 'backwards'.
The vane also seems to be spinning quite erratically.

Those observations (particularly the erratic wind vane) suggest an "extreme local" situation.

A useful longer-term observation would be whether the erratic nature of the measurements depends on wind direction (e.g., more reasonable when wind is from the North than when wind is from the West...)

One or two pictures of the area might help us understand.

[ocala]

Out of interest, how much did you have to pay the aerial person to do it? If you don't mind me asking.. I'm dithering whether or not, to stick mine up on my chimney .. It means having to buy a wireless transmitter (not sure how much they are)
I live in a house owned by a housing association, so the maintenance guys have roof ladders etc.. I was thinking of chucking them 20 quid to do it. I have a bracket that is ready to be screwed in, that will hold an 8' pole, so 4' would be above the chimney pots. The chimney itself is 11m up, it'd be a nightmare is something fails on the anemometer again.

Just curious. Are those chimneys still in use?

[Mapantz]

Not any more, as I have central heating now. The chimney got rebuilt two years ago, as it started to crumble and bricks fell down inside (not surprising when it is 112 years old) and there was monumental leaking. It's double chimney too, so it's rather large.

[Paul]

Out of interest, how much did you have to pay the aerial person to do it? If you don't mind me asking.. I'm dithering whether or not, to stick mine up on my chimney .. It means having to buy a wireless transmitter (not sure how much they are)
I live in a house owned by a housing association, so the maintenance guys have roof ladders etc.. I was thinking of chucking them 20 quid to do it.

About 3-4 times that which I thought was steep, should have got multiple quotes but I was keen to get it up there!
Though to be fair he was there quite a while and did resite it with an extra clamp on the pole.

[Paul]

Well mystery solved and frankly I am almost too embarrassed to share why 

In my defence the Aerial guy fitted the new anemometer into the black mounting bracket whilst I was working on the transmitter.
Though of course I should of immediately spotted it, expensive mistake.

Out came the camera today... zoomed in...
Ready? Here we go....

 [ You are not allowed to view attachments ]

So the arm needs rotating 180 degrees and we should be all sorted.
Don't know whether to laugh or cry!

[Mapantz]

Pohahahhahhaha !!

I shouldn't laugh, but that has to the best picture I have ever seen!

The aerial guy should rectify that free of charge to be fair. Props to you for sharing the photo though.

[dalecoy]

One or two pictures of the area might help us understand.

I'm pleased that I could assist................

[CW2274]

I......I.....um....I......

[ocala]

Ah, that's funny.
Made my day.

[Paul]

Glad I have provided some amusement 

Yes dalecoy, good idea, thanks.

[dalecoy]

I suppose I should also take credit for observing:

Those observations (particularly the erratic wind vane) suggest an "extreme local" situation.

 

[ocala]

I suppose I should also take credit for observing:

Those observations (particularly the erratic wind vane) suggest an "extreme local" situation.

 

Awesome

[CW2274]

Glad I have provided some amusement 

Yes dalecoy, good idea, thanks.

You didn't give him anything sharp, or let him work on the rest of your place, did ya?

[WxLover16]

I can just imagine this guy installing it and thinking to himself "what the hell is this and how does it go?" lol definitely would get him to rectify the situation free of charge. His screw up. Ever seen the movie observe and report? You should do that. You observed a mistake, now report it to the guy.

[Paul]

To be fair to the guy, it is entirely my fault.
We had the pole down on the ground to replace it and I somehow just didn't notice it before he took it up on the roof.

[dalecoy]

To be fair to the guy, it is entirely my fault.
We had the pole down on the ground to replace it and I somehow just didn't notice it before he took it up on the roof.

Many of us (myself included) have made "did not notice until it was too late" errors.

Few of us have publicly acknowledged that, with pictures.

Thanks, Paul!

[Paul]

Many of us (myself included) have made "did not notice until it was too late" errors.

Few of us have publicly acknowledged that, with pictures.

Thanks, Paul!

  Indeed, i've made many, but usually I keep them to myself!

[Old Tele man]

Maybe time to do some casual reading on the subject of wind "Vortex Shedding"?

[dalecoy]

Maybe time to do some casual reading on the subject of wind "Vortex Shedding"?

Do you really think that was the major problem shown here?

[Old Tele man]

Maybe time to do some casual reading on the subject of wind "Vortex Shedding"?

Do you really think that was the major problem shown here?

Nah, label on the box reads: OTHER SIDE UP.

Just anticipating possible future 'problems' from one specific wind direction (wink,wink).

[CW2274]

Yeah, but, if he gets under a micro-burst, he'll be all set.