[time-nuts] [OT] degausing
dave.martindale at gmail.com
Thu Apr 15 20:34:59 EDT 2010
In the case of compasses, a balanced needle tends to tilt to align with the
vertical as well as horizontal component of the earth's magnetic field - so
it's level at the equator, north end low in the northern hemisphere, and
south end low in the southern hemisphere. But you want the needle level so
it doesn't drag on the capsule and so the pivot works the way it was
designed. So northern hemisphere compasses have excess weight on the south
side in order to give an approximately level needle despite the tilt in the
magnetic field in that area.
Recta makes compasses with magnet and pointer as two separate parts, linked
by a bearing whose axis goes east-west. The magnet is free to tilt. The
needle indicates the azimuth portion of the magnet position, but ignores any
tilt component and remains level in the capsule. They call it a "global"
compass because a single version works everywhere (that a compass can be
used at all).
However, I don't see how the earth's tilted field prevents a CRT from being
used in both hemispheres. I can see how it might need to be realigned,
since it uses permanent magnets on the yoke and their field will be
influenced by the earth's local field. But a different model for the
On Thu, Apr 15, 2010 at 5:07 PM, wa1zms at att.net <wa1zms at att.net> wrote:
> FWIW.....A good high quality compass needs to be designed based on what
> region of the earth you plan to use it in. The Suunto ones I have are marked
> with a US region code.
> -Brian, WA1ZMS
> On Apr 15, 2010, at 7:58 PM, Kit Scally <kScally at BYTECAN.com.au> wrote:
>> If memory serves me correctly, Philips "better quality" PAL colour TV's
>> in the late 70's to early 80's "inverted" the CRT for us in the Southern
>> Hemisphere. The TV's were clearly marked as such on the packing box.
>> For reasons unknown, Japanese-made colour TV's never seemed to have this
>> problem. Even though I was working professionally with these beasts at
>> the time in a TV station, I never figured out why Jap TV's seemed immune
>> to this problem whilst those made by our Dutch friends were not.
>> OOLLM I guess.
>> Message: 4
>> Date: Thu, 15 Apr 2010 08:21:03 -0700
>> From: "Craig S McCartney" <CMcCartney at on-sitetraining.com>
>> Subject: Re: [time-nuts] [OT] degausing
>> To: "Discussion of precise time and frequency measurement"
>> <time-nuts at febo.com>
>> <9FEDD04E51E8C045BC6FBCBC49346072381C86 at smbuserver.On-SiteTraining.local
>> Content-Type: text/plain; charset="us-ascii"
>> A bit off topic, but likely interesting to time-nuts:
>>> So, we had a HDTV monitor that doubled as a earth hemisphere detector,
>> using magnetic flux differential. Needless to say, we only used it in
>> northern hemisphere shows after that.
>> Craig McCartney
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