Hallo.
Also. Da hier ja allgemeine Unstimmigkeit zu herrschen scheint, ob Magnetfelder (oder durch sie induzierte Spannung) der Pumpe den Computer beeinflussen können, habe ich mal meinen Lieblingsreviwer Dan von www.dansdata.com befragt. (Dazu habe ich schamlos Lothars Messergebnisse zitiert.)
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Ich:
On German watercooling fora, the newest buzz is that the
magnetic field and the current induced by water pumps are harmful to computer circuitry and hard disks.
Dan:
Well, maybe, if you've got a nasty sparky brush motor in your pump. I strongly doubt magnetically coupled pump motors pose any threat. Their external magnetic field is laughably small compared with what's needed to wipe a floppy disk, much less a hard drive, and the induced voltages you
mention...
The results:
directly at the pumps casing (in mVeff)
-on top: 4 mV
-at the side: 7 mV
-back: 1 mV
-front: 0.6 mV
at a disctance of 8cm
-on top: 0.7 mV
-at the side: 0.2 mV
-back: 0.2 mV
-front: 0.2 mV
...are a long, LONG way below the one-point-something volts that's the lowest signal voltage that I think you'll find anywhere in a modern PC. Unless something in the PC's really, _really_ good at picking up these emissions, and really, _really_ sensitive to noise, I don't think you'll see any effect.
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Betreffend PC-Speaker und ihre Wirkung auf Platten antwortete er letztens einem anderen besorgten Leser seiner Seite (siehe
http://www.dansdata.com/io014.htm):
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The way to wipe data on magnetic media is by applying a field beyond a certain threshold strength, determined by the kind of magnetic media you're talking about, and then, preferably, causing that field to oscillate.
A hard disk platter spinning through the field created by a small magnet will experience considerable changes in the relative field strength over each part of its surface as it rotates. Which gives you your oscillation. PC speakers all fail the first test, though, even if you press them up against the outside of the drive. They're just not strong enough.
The coercivity (field strength needed to erase data) of a modern hard disk platter is a few thousand Oersteds; you need a magnetic field strength of exactly the same number of Gauss to affect it. If the field strength is below the coercivity, it'll make no difference at all to the data. It won't slowly wear it away over time. It'll do nothing. Welcome to quantum physics, please enjoy your stay.
As a general rule of thumb, magnetic field strength drops off as the inverse cube of the distance from the middle of the magnet. That's not exactly how it works, but it's all you need to know for computer- protection purposes.
A ferrite-magnet speaker will have a peak field strength, measured right on the magnet surface, of about one thousand Gauss. That's already too little to hurt a hard drive. Move a centimetre or two away, which is where drive platters will be relative to the magnet if the speaker's resting on top of the drive casing, and you'll already be down to a couple of hundred Gauss, if that.
In a normal PC case, even one with a drive cage right over the speaker, no part of the platter will see more than a hundred Gauss. Plain 3.5 inch high density floppies have a coercivity of 720 Oersteds; you can't even wipe a floppy with a speaker magnet that isn't almost touching it.
On top of all this, some PC speakers are magnetically shielded, with a second, reversed magnet glued onto the back of the main magnet assembly, usually under a metal cap. They've got not much external field, no matter where you measure it.
The tiny electromagnets in disk drive write heads manage to do their job because the strength of their weeny little field is actually rather high, and they're very, very close to the platter.
Rare earth permanent magnets have a surface field strength of about 10,000 Gauss; laying a good-sized one of those on top of a hard drive might well wipe some data. But ferrite speaker magnets haven't a hope, no matter where they are.
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Ich hoffe das hilft jemandem.
Wraith.