sean@geac.UUCP (Sean Phelan) (02/15/89)
I've just received a message from a colleague in Australia. The local
representative of Wyse Technology, whose terminals we are starting to
use all over the world, is saying that the terminals have to be aligned
differently in the Southern hemisphere, because the magnetic flux of the
Earth goes the opposite way.
Now, this sounds to me like complete b*llsh*t, perhaps the kind of story
a salesman uses to get a local order. When I try dividing the Earth's
magnetic flux into it's x,y,z vector components and look at how they
affect a terminal, I conclude that a North facing terminal in the Northern
hemisphere is going to be affect in EXACTLY the same way as a South facing
terminal in the Southern hemisphere.
However, I might have overlooked something. So my questions to the Net are :
Does a terminal experience any effects from the Earth's magnetic field, and
if so do these effect differ between the Northern and Southern hemispheres ?
Thanks,
Sean
PS - if, as I very strongly suspect, the Wyse salesman is just trying it on,
I would NOT suggest that anybody call their Wyse rep. complaining that
they have received a Southern hemisphere terminal at a Northern
hemisphere site. To do so would be very irresponsible indeed.
I advise against it.
--
Sean Phelan Geac Computer Corporation, Markham, Ontario
sean@geac
{uunet!mnetor,yunexus,unicus,utgpu}!geac!seanjmunro@wyse.wyse.com (Jim Munro) (02/16/89)
In article <6569@geac.UUCP> sean@geac.UUCP (Sean Phelan) writes: >I've just received a message from a colleague in Australia. The local >representative of Wyse Technology, whose terminals we are starting to >use all over the world, is saying that the terminals have to be aligned >differently in the Southern hemisphere, because the magnetic flux of the >Earth goes the opposite way. > >Now, this sounds to me like complete b*llsh*t, perhaps the kind of story >a salesman uses to get a local order. When I try dividing the Earth's Beleive it or not, this is all true. Terminals are indeed affected by the earth's magnetic field and will appear out of allignment if they are shipped from one hemisphere to another. The effect is a 'rotation of the screen image'. This is not a very big mis-allignment but it is enough for major customers to reject profduct because they may no longer meet our stringent allignment specs. Wyse has installed a system in our Taiwan plant which can emulate the magnetic field in any part of the world. This is used to allign units going to the southern hemisphere. Years ago, we had a similar problem with units going to Europe. At that time the solution was to allign the units while they were facing north-south. This solves the problem for Europe but not for Austrlaia. I hope this restores your trust in our sales reps. Jim Munro WYSE Technology. ZZ
palmer@tybalt.caltech.edu (David Palmer) (02/16/89)
In article <6569@geac.UUCP> sean@geac.UUCP (Sean Phelan) writes: >I've just received a message from a colleague in Australia. The local >representative of Wyse Technology, whose terminals we are starting to >use all over the world, is saying that the terminals have to be aligned >differently in the Southern hemisphere, because the magnetic flux of the >Earth goes the opposite way. > >Now, this sounds to me like complete b*llsh*t, perhaps the kind of story >a salesman uses to get a local order. When I try dividing the Earth's >magnetic flux into it's x,y,z vector components and look at how they >affect a terminal, I conclude that a North facing terminal in the Northern >hemisphere is going to be affect in EXACTLY the same way as a South facing >terminal in the Southern hemisphere. The vertical component of the magnetic field is the opposite in the two cases (south facing in south hemi. vs. n-facing in n-hemi) even though the horizontal components are the same (roughly). This causes the electron beam in the CRT to curve to the side in opposite directions in the two cases. The question is, 'Is this important?' For a quantitative understanding, the radius of gyration of a particle with charge Z (-1 for an electron, ignore the minus sign) and energy E keV (~15 keV for a monochrome terminal, more for color, all numbers are approximate) in a field of B gauss (it is ~1/2 for the Earth, the z-component is less still, call it 1/4 gauss just to be simple) is: R (cm) = E (eV)/ (300 Z B (gauss)) R = 200 cm. Over a 20 cm path from the gun to the screen, the beam is deflected by ~ 1mm (20 cm * (1 - cos(20/200 radians)). This means that the whole image is shifted (horizontally) on the order of a millimeter. This may be important for color systems with their shadow masks, but I doubt that it makes much difference in a monochrome system. As a sanity check, pointing the terminal East instead of West should cause a similar vertical shift. This seems to work okay. Just remember, the creature you meet when you talk to customer service is designed to sell, and he doesn't care whether its toothpaste, terminals or weapons systems. As long as he extracts money from your pocket into his company, he is successful. Giving him the benefit of the doubt, he may have noticed that the terminals he gets are often badly aligned. This may be due to rough shipment, but he may think that it is due to the magnetic field. David Palmer palmer@tybalt.caltech.edu ...rutgers!cit-vax!tybalt.caltech.edu!palmer "I was sad that I had no shirt, until I met a man with no torso"
berger@clio.las.uiuc.edu (02/17/89)
And if you think the earth's magnetic field is too weak to have a noticeable effect on anything, you'd have trouble believing that magnetic compasses work. Mike Berger Department of Statistics University of Illinois berger@clio.las.uiuc.edu
) (02/17/89)
In article <6569@geac.UUCP>, sean@geac.UUCP (Sean Phelan) writes: > I've just received a message from a colleague in Australia. The local > representative of Wyse Technology, whose terminals we are starting to > use all over the world, is saying that the terminals have to be aligned > differently in the Southern hemisphere, because the magnetic flux of the > Earth goes the opposite way. I do have problems with my eye-glasses too... I bought them in EUROPE!!! --- ___ ____ ___ ======================= | / | /\ |\ | | | / / \ | | Kianusch SAYAH-KARADJI |/ | / \ | \ | | | \___ | |____| {!pixar!unicom!sayah_k} |\ | /----\ | \ | | | \ | | | ======================= | \ _|_ / \ | \| \___/ ____/ \___/ | |
rauletta@gmu90x.UUCP ( ) (02/20/89)
In article <420@unicom.UUCP> sayah_k@unicom.UUCP (KIANUSCH... Oh, no! It`s this guy again !!!) writes: >In article <6569@geac.UUCP>, sean@geac.UUCP (Sean Phelan) writes: >> I've just received a message from a colleague in Australia. The local >> representative of Wyse Technology, whose terminals we are starting to >> use all over the world, is saying that the terminals have to be aligned >> differently in the Southern hemisphere, because the magnetic flux of the >> Earth goes the opposite way. > >I do have problems with my eye-glasses too... I bought them in EUROPE!!! > In early days of color television it was recommended that the final alignment of the electron beams be performed after the set was installed due to the influence of the Earth's magnetic field has on the convergence of the beam's and the resulting poor alignment of the three colors as seen on the screen. Better sets had Mu-Metal shields to reduce the effects of stray magnetic fields. I have noticed that the convergence of some of my sets seem to get better and worse as their postion is changed. But whether this is due to stray magnetic fields or getting bounced around is anyone's guess. But I don't see how just being in the Southern Hemisphere would make any difference. One side note. The famous compass maker, Brunton, used to require that you tell them whether their top of the line model was to be used in the Northern or Southern Hemisphere. Later on it was announced that the "new and improved" model could be used in both hemispheres with equal accuracy. As far as I know there where no apparent differences in the Southern model and the Northern model. Hope this trivia sheds some light on the question. --Richard Auletta rauletta@gmu90x.gmu.edu
-Rich-@cup.portal.com (Richard Sherman Payne) (02/21/89)
This is a very interesting idea, but conceptually I can see ne reason for it. The corialis force is different in the southern hemisphere, but the magnetic field is in the same direction as in the northern hemisphere. Unless there is some other mechanism involved, it sounds bogus to me. But one difference I can think of is that the power is at a different frequency and voltage in australia. I believe that it is 50 HZ at 220 V, but I am not positive. 60 HZ moniters will not work at 50 HZ, so that might be the reason for the different moniters. Just my idears Rich -Rich-@cup.portal.com
ron@hpfcmr.HP.COM (Ron Miller) (02/23/89)
Re: Magnetic Fields and CRT performance Indeed there is a difference in performance of color CRTs in Australia. Hewlett-Packard has had several different product designs over the last 5 years for color displays. All of them were affected by the difference in the Earth magnetic field between where the unit was aligned and where it was installed in Australia. Not all of them were severely affected but it quite true that there is an effect. One report for a delta gun CRT was that each of the gun colors was shifted by one on a particular unit. (I have my doubts but it makes a good story!) Ron Miller H-P Colorado Computer Manufacturing Operation
mjb@xpiinc.UU.NET (Michael J. Braca) (02/24/89)
OK, here is the scoop. It turns out that the terminal misalignment problem (i.e. a terminal aligned in the US will not appear aligned in the southern hemisphere) is really mostly a problem in Australia only, and is not directly related to hemisphericity. Australia is very close to the magnetic south pole and the magnetic field there deviates significantly from the horizontal. You would have a similar problem near the magnetic north pole. Mike Braca Visual Technology, Inc.
xiaoqin@ccnysci.UUCP (Xiaoqin Guo) (02/25/89)
In article <1765@gmu90x.UUCP> rauletta@gmu90x.UUCP ( ) writes: >In article <420@unicom.UUCP> sayah_k@unicom.UUCP (KIANUSCH... Oh, no! It`s this guy again !!!) writes: >>In article <6569@geac.UUCP>, sean@geac.UUCP (Sean Phelan) writes: >>> I've just received a message from a colleague in Australia. The local >>> representative of Wyse Technology, whose terminals we are starting to >>> use all over the world, is saying that the terminals have to be aligned >>> differently in the Southern hemisphere, because the magnetic flux of the >>> Earth goes the opposite way. >> >>I do have problems with my eye-glasses too... I bought them in EUROPE!!! >> > Better sets had Mu-Metal shields to >reduce the effects of stray magnetic fields. I did the following experiment to see the effect of magnetic field on color TV: I use a permanent magnet in the shape of cylinder with 1" diameter and 1" height. When I put it beside my TV ( Brand Emson, made in Taiwan, 19" ) very little effect. But when I put it in front of TV screen, the portion directly facing the magnet change colors into either purple or red , depending on whether N or S is pointing the screen. The spot size is around 3" . Anyone interested may do the experient. But warning : Don't use a strong magnet. The changed spot will remain the same color even after the magnet is no longer there ! If that happen, try to use the "other " polarity" which causing your problem to demagnetize. base on some calcalation and experiemnce working with electron beams, I think it is possible that the differnce between North and South Hemisphere magnetic field could be a problem . Even if there is u-metal shielding, the field can definitely penetrate, althought significantly reduced, through the screeen plan. This is probably why there is no effect when the magnet is beside the TV.
msb@sq.com (Mark Brader) (02/27/89)
> Australia is very close > to the magnetic south pole and the magnetic field there deviates > significantly from the horizontal. You would have a similar > problem near the magnetic north pole. Some quick computation gives the following rough figures: South Magnetic Pole to Melbourne 1900 miles South Magnetic Pole to Sydney 2200 miles North Magnetic Pole to Winnipeg 1800 miles North Magnetic Pole to Chicago 2350 miles North Magnetic Pole to Toronto 2350 miles North Magnetic Pole to New York 2500 miles In other words, significant parts of North America *are* "near the magnetic north pole"; therefore the problem would be particularly bad if the terminals originated in those areas. Actually, the magnetic dip angle doesn't vary in any simple fashion with distance from the magnetic pole, but I don't have a map at hand showing how whether the situation suggested by the above distances is in fact true. It's a reasonable first guess, though. Mark Brader, Toronto "If the standard says that [things] depend on the utzoo!sq!msb phase of the moon, the programmer should be prepared msb@sq.com to look out the window as necessary." -- Chris Torek