EHEIM pump EMI
 

Hi all!
I was wondering how much if any EMI the EHEIM 1250 pump puts out. I have 4 HDDs that wil sit about 1", 2", 3" and 4" away respectively. Just wanted to know if there might be any magnetic fields which degrade my HDDs. Thanks!

The 1250 has a very low EMI, so i don't think it will be a problem.

Actually, at work we tried to kill a 10 gig drive (IBM) with a huge frickin magnet from some PA speaker. We let the magnet rest on the drive for a few days but all of the data was intact. That was a mind-blower..
So I'm not a least bit concerned about wiping data of my drives anytime soon.. the drive will have failed due to mechanical problems before that.

Wow! Thanks for that great info, Nordic!

Magnets themselves have a magnetic field, but don't actually generate EMI field, but a MOVING magnet does! In the test above, the disk drive platter was spinning at at least 5400 rpm (right Nordic?) which has the same result.

EMI comes from just about any AC powered device, simply because the voltage changes from 0 to +170V to 0 to -170V (hence 120 Vac, which is RMS, with a peak at 170V) in a nice sine wave.

Actually static magnets (fields) are the most disruptive for magnetically stored media, so we didn't have the disk plugged in - the magnet and disk were "not moving". Actually the data stored on disk is less prone to damage when it's running because of the reason you mentioned!
EMI might disrupt data communication between disk and motherboard but you need the correct amplitude and frequency to cause transmission errors.

Heh, I better talk to the electrical engineer at work who got the idea, in case my claims aren't correct. :)

Sooo... whatever magnetic field is produced by the pump will not corrupt data or send the head crashing into the platter. Sounds good. Thanks!

Check with him...

Fixed magnets are bad for magnetically stored media, because the movement of the magnet towards the media creates an increase in magnetic field strength (from the tape/HD point of view) which is a varying magnetic field, aka EMI. Keep them at a fair distance, and everything is fine, but rev up the HD platter to 5400 rpm, and wait...

Try the HD thing again, but power it up, not connected to a PC. I can guarantee you that you will never see a HD so messed up:eek:

The explanation I got was:
A professional degausser/eraser works with fluctuating magnetic fields but the purpose of that is to totally randomize the data. The effect of applying a static magnetic field is that you would be able to distinguish recorded data easier as some parts of the media were probably already aligned with the tape but the parts that weren't will still differ slightly (less and less the stronger the field).

(translated to english from swedish)

Actually, I've tried an AC degausser/demagnetizer on floppy disks: it's just a big coil. Surprisingly, some floppies actually came out intact! (Thanks Radio-Scrap!):mad:

Again though, because the voltage changes (AC), it creates a varying magnetic field. The variation in magnetic field can be translated in some unit of measure (I don't remember which, that part of physics was a long time ago!). A fixed magnet's field doesn't move, unless you move the magnet, or move the object near/around the magnet...

c'mon... won't you try to trash that HD for us? In the interest of science...:dome:

But with regards to watercooling and pumps, there is absolutely no problem with having an aquarium pump inside your computer. They are shielded to begin with (all EHEIMs are), and so are hard drives. An immense magnetic field is required to erase even a floppy disk and my engineering friend assures me that I have nothing to worry about. He said something about the non-existance of a device that could completely wipe a modern hard-drive, that sounds wicked!

As a test I put my pump in front of my monitor and noticed only slight discoloration when the pump housing was a couple of centimeters from the glass, even the smallest loudspeaker has a stronger field than that.

I will try to find that drive again, it's on a shelf somewhere in storage. In the name of science, yeah ;)

Yep, right on! We really don't have to worry about EMI from a pump inside a case. (Shielded or not, if you ask me).

Monitors though are sensitive to fixed magnets (and EMI too!), because the point of color is actually an electron beam hitting the screen, and it is directed by magnetic deflection (hence the big coils behing the tube). So a magnet will make a monitor/tv do weird things...

Not to say that they'll break or anything: they'll just discolor, temporarily. Monitors usually degauss themselves on startup now (wasn't like that 10 years ago). TVs though, don't usually have a degauss circuit...

I sat my 1250 next to my TV. No effect, while even a speaker distorted it.

yeah, but was the pump on??

Yes, of course my pump was running. Don't know about redleader's..

yeah, i was talking about redleader's :p

Magnetic fields units-> Tesla i believe.

tesla coils are sick

My Eheim 1048 isn't shielded too well, if I move set i too close to my monitor, then it starts flickering, it has to be atleast 60cm's away from it :confused:

WoW! That's not my experience at all, I had to bring it up real close to the monitor to experience color perturbation. Of course your monitor might not be as well shielded as my Trinitron, but in any case I wouldn't worry. Electron guns are very sensitive to magnetic fields as you can imagine and can't be compared to magnetic media.