Electricity ****** *******s

[mdklatt]

How do I know if I'm dealing with an "electrically noisy environment", thus necessitating a (more expensive) Hall effect anemometer instead of a regular anemometer. The environment in question is apparently an 80 foot stadium light tower out in the middle of BFE.

[ChickSoonerFan]

Well I understood the BFE part...the rest was a little fuzzy.

[skycat]

Do you have a part number, or better yet a link to the spec of the Hall effect sensor in question?

That light tower is going to produce 60 cycle noise. Depending on the type of lighting elements, there could be more noise on top of that. To quantify that, you'd have to get an E-field sensor. But even if you know the kind of noise you'd have to put some kind of limits on how electrically noisy an enviornment your instrument can handle.

Long story short, need more info.

[BlondeSoonerGirl]

I think he needs to tighten his ricktabacken.

[12]

That's just cockytalk.

[mdklatt]

Do you have a part number, or better yet a link to the spec of the Hall effect sensor in question?

That light tower is going to produce 60 cycle noise. Depending on the type of lighting elements, there could be more noise on top of that. To quantify that, you'd have to get an E-field sensor. But even if you know the kind of noise you'd have to put some kind of limits on how electrically noisy an enviornment your instrument can handle.

Long story short, need more info.


regular anemometer (http://www.nrgsystems.com/store/product_detail.php?cd=11&s=1899)


Hall effect anemometer (http://www.nrgsystems.com/store/product_detail.php?cd=11&s=1901)


We're also installing a wind vane (http://www.nrgsystems.com/store/product_detail.php?cd=11&s=1904). There is no Hall effect wind vane available. The wind vane signal is voltage instead of frequency, so I guess we don't have to worry about interference?

:confused:

[sooner_born_1960]

I usually just look at the trees and say something like; "Pretty windy, huh?".

[mdklatt]

I usually just look at the trees and say something like; "Pretty windy, huh?".

That makes it difficult to calculate the wind power density. :cool:

[sooner_born_1960]

OK, you got me. I'm not an electricity ****** *******, nor did I stay in a Holiday Inn Express.

[Howzit]

I stuck a coat hanger in a wall socket when I was a kid, if that helps...

[mdklatt]

I stuck a coat hanger in a wall socket when I was a kid, if that helps...

It does explain a lot.

[Howzit]

Why is that always the response when I tell that story?

[mdklatt]

Why is that always the response when I tell that story?

I know somebody who was struck by lightning twice. I told him he needs to tell people that as soon as they meet him because it answers a lot of questions. :D

[afs]

Long story short, need more info.

or you could put up the first one and if you can tell your readings aren't accurate then you buy the more expensive one.

duh

[mdklatt]

or you could put up the first one and if you can tell your readings aren't accurate then you buy the more expensive one.

duh

Except for the twelve-hour round trip to the installation site this isn't a bad idea.

:twinkies:

[Czar Soonerov]

How do I know if I'm dealing with an "electrically noisy environment", thus necessitating a (more expensive) Hall effect anemometer instead of a regular anemometer. The environment in question is apparently an 80 foot stadium light tower out in the middle of BFE.

Yeah. 220... 221, whatever it takes.

[Sooner Eclipse]

How do I know if I'm dealing with an "electrically noisy environment", thus necessitating a (more expensive) Hall effect anemometer instead of a regular anemometer. The environment in question is apparently an 80 foot stadium light tower out in the middle of BFE.

Is there any other electrical equipment that will have wiring in the same proximity as this device?

Does the tower actually have lights on it? Any other measuring equipment or just the anemometer?

If it is going to be the only device on the tower, then it is definately not going to be exposed to "electrical noise". However if there are other devices on the tower then it just depends on what they are, AC vs. DC, and how much current the other devices are using.

If the pole has lights stadium lights on it (A/C, high current, high voltage) then if the signal wire from the anemometer will need to be kept well away from the power wires for the lights or at least well shielded. (grounded cover surrounding the signal wire)

If the pole just has other low voltage measuring equipment on it than most likely that the analog device(regular) will be fine. If you are worried about "noise" being induced from other devices then get the digital device. (hall effect)

BTW, if you go with the hall effect device you will need to supply it with a DC current. If you use the analog device it will not need an external power supply.

[12]

Behold the beauty of the South Oval!

[Sooner_Bob]

Just don't pee on an electric fence.

[mdklatt]

If the pole has lights stadium lights on it (A/C, high current, high voltage) then if the signal wire from the anemometer will need to be kept well away from the power wires for the lights or at least well shielded. (grounded cover surrounding the signal wire)


The "wire" in this case is actually two or three wire insulated wires plus a bare wire all inside a sheath of insulation. The manufacturer calls this a shielded cable with drain wire (http://www.nrgsystems.com/store/product_detail.php?cd=11&s=1930).




If the pole just has other low voltage measuring equipment on it than most likely that the analog device(regular) will be fine. If you are worried about "noise" being induced from other devices then get the digital device. (hall effect)


We've installed sensors on cell towers in some cases--same problem as the light pole? I wasn't involved with those, so I have no idea if Hall effect sensors were used.



BTW, if you go with the hall effect device you will need to supply it with a DC current. If you use the analog device it will not need an external power supply.

The sensors and the data logger we're using are all from the same manufacturer and are designed to work together. The high-dollar anemometer requires an extra connection to the logger. I have no idea why, but maybe this is to supply power from the battery-powered logger. How much power/current are we talking about? The logger runs on two 9V batteries in parallel. I think...whichever arrangment give you the same voltage with two batteries as with one.

[nanimonai]

Just remeber to adjust the TG scope to EXACTLY 124587.29 X 1477(-7) that way it will allow enough slack for the TS scope to fluctuate within a safe range of around 97.2 cycles per second. If you want to bypass the TG/TS altogether you could simply maginify the RS signal by reversing the positive flow to around 36.7hz.

[12]

Well, DUH!!?!!

[Sooner Eclipse]

The "wire" in this case is actually two or three wire insulated wires plus a bare wire all inside a sheath of insulation. The manufacturer calls this a shielded cable with drain wire (http://www.nrgsystems.com/store/product_detail.php?cd=11&s=1930).

Most analog devices need only a signal wire and a signal ground. (2 wires) The shielding you describe sounds more than adequate. This setup would probably work but only an electrical engineer could tell you for sure after knowing the practicals of the location.



We've installed sensors on cell towers in some cases--same problem as the light pole? I wasn't involved with those, so I have no idea if Hall effect sensors were used.

I have no experience with cell towers but would guess that the use an awful lot of power. Anything that uses a lot of current, especially A/C current will generate magnetic fields. These fields are what induce interference into other wires in range of the field as these fields collapse and expand (at 60Hz for AC current) So yea, probably the same problem


The sensors and the data logger we're using are all from the same manufacturer and are designed to work together. The high-dollar anemometer requires an extra connection to the logger. I have no idea why, but maybe this is to supply power from the battery-powered logger. How much power/current are we talking about? The logger runs on two 9V batteries in parallel. I think...whichever arrangment give you the same voltage with two batteries as with one.

Thats exactly why. It(the digital) needs an extra wire to supply between 5-24 Volts DC to operate based on the link you supplied earlier. Hooking 2 9V batts together in parallel still give you 9V, just twice the reserve capacity.

If you are mounting it on cell towers, the digital is probably the safe bet.

[Sooner Eclipse]

Just remeber to adjust the TG scope to EXACTLY 124587.29 X 1477(-7) that way it will allow enough slack for the TS scope to fluctuate within a safe range of around 97.2 cycles per second. If you want to bypass the TG/TS altogether you could simply maginify the RS signal by reversing the positive flow to around 36.7hz.

Damn..... everybody's a smartass around here.:D

Just tryin to help a sooner out.;)

[AlbqSooner]

Here is the extent of my knowledge of electricity:

1. It is invisible.

2. It will bite, and can kill, you.

3. It does not countenance a fool.

4. I can hire someone else to deal with it.

[skycat]

Jeebus I wish I could get away with writing specs like those. Almost none of the data that I was after was in that.

I did find this in the copy of the cheaper version though:


Our equipment was tested for interference during our application for a 'CE' mark, so we can supply this information upon request. Our Symphonie logger is also certified for compliance with FCC standards (the FFC is the government agency that oversees broadcast-related issues in the USA).

From that my guess is that as long as you hook everything up correctly, you'll be A-OK with the chearper version. Just do your best to stay away from the lines that are powering the lights and keep all of the wiring as short as possible.

The cell towers would be radiating a crap-ton more interference than the power lines in this stand, so that's not a real good comparison.

Of course, EMC isn't my area, but if it were me, and the price difference is any more than trivial, I'd go with the cheaper one.

[OklahomaRed]

Just don't pee on an electric fence.


Actually, if you standing on the back of a cotton trailer you can. Don't ask me how I know that. :)

[mdklatt]

From that my guess is that as long as you hook everything up correctly, you'll be A-OK with the chearper version. Just do your best to stay away from the lines that are powering the lights and keep all of the wiring as short as possible.


We're supposed to get pictures of the tower, but we won't lay eyes on it until we drive out to the panhandle for the installation. I don't even know if our mounting hardware will fit on it. All the stuff we have is designed mainly for the purpose-built towers provided by the manufacturer. And do I need to add I've never done any of this before?



Of course, EMC isn't my area, but if it were me, and the price difference is any more than trivial, I'd go with the cheaper one.

The difference is definitely more than trival for us. We already have regular anemometers we can use.

Thanks for all the advice. Do you know of any good online references for this stuff that I can show the boss person?

[skycat]

Off the top of my head, I don't know of anywhere specific to look. And when I google EMC or radiated emissions I see a bunch of stuff that's probably a bit more detailed than your boss wants to look at.

The division expert on EMC (electromagnetic compatibility by the way for anyone silly enough to read this and who is curious) sits down the hall from me, I'll ask him tomorrow assuming he's in. He's always off-site on some boondoggle or another.

[mdklatt]

He's always off-site on some boondoggle or another.

Does he ever get out to the panhandle? ;)

[RacerX]

I feel the need to type flux capacitor.

[Sooner_Bob]

http://www.hboasia.com/images/posters/378x195/back_to_the_future.jpg

[mdklatt]

Some more questions. If there is EM interference from the light tower it will only happen when the lights are on, right? And the nature of the interference will be a very strong signal at 60 Hz, right? According to the transfer function for the anemometer, 60 Hz corresponds to a wind speed of 46 m/s. That's way outside the normal range of wind speeds the tower will experience, so if we get 46 m/s wind speeds every time the lights are on we know interference is a problem, right? And we don't need to worry about interferance with the wind vane because it's signal is voltage, not frequency?

[skycat]

Well, the EMC guy isn't here today. That guy is never around. But I'll try to answer some of your questions.


Some more questions. If there is EM interference from the light tower it will only happen when the lights are on, right?

Unless they've got something else they're powering up there than yes, which is why I think you'll be fine.


And the nature of the interference will be a very strong signal at 60 Hz, right?

yup


According to the transfer function for the anemometer, 60 Hz corresponds to a wind speed of 46 m/s. That's way outside the normal range of wind speeds the tower will experience, so if we get 46 m/s wind speeds every time the lights are on we know interference is a problem, right?

Well, maybe, maybe not. Probably the noise won't be so strong as to completely overwhelm the signal. Perhaps more likely will be your signal and the noise overlapping. Imagine a sinusoid at 60Hz on top of another at 20 Hz.

Another possiblity is that the noise will be picked up in the sensor itself, which could also cause you to have nonsensical data.

But your underlying point is valid. If you find that the data goes crazy Friday nights at 5:30 and goes back to normal at 10:00, you'll know what the problem is.


And we don't need to worry about interferance with the wind vane because it's signal is voltage, not frequency?

Pretty much. A steady state signal doesn't radiate very much EM interference. Besides that, it won't have much power behind it.

But overall, I'm still going to guess that even when the lights are on, you're shielding will be adequate to give you a signal. I do expect you to have glitches whenever the lights are powered on or off though. But I'm guessing that doesn't bother you too much.

[afs]

ttt