Do not buy Holsters with Magnet Latches!!!

[extorian]

Well, I also agree that it's better to be safe than sorry, sure - and that's anyone's perogative.

It's also a good point that there may be other ferrous materials in the phone near to the chip that sense the Hall effect. Indeed, if these became sufficiently magnetised it could throw the sensor off. However, I do doubt this as firstly I doubt there's sufficient, if any, ferrous materials near by (they're liable to rust), and I doubt they'd become sufficiently magnetised.

I don't know how long it takes the phone to dynamically recalibrate after being near a magnet, but what I do know is that my phone is next to the magnetic clasp on a "Krusell Horizon Leather Case with Multidapt - S-Wide" most of the time, and by the time I've removed my phone from the holster, unlocked the screen, and opened the compass app, it all seems to work absolutely spot on. So why would my phone be fine next to such magnets and other's require being hit to fix it? Ok, perhaps it's because the magnet is in a different position on my holster relative to the phone...

While I don't doubt your experience at all, what I would be wary of is advocating that people hit or bang their phone in order to fix this problem. It's not very scientific, and the G1 has no moving parts (other than the buttons, hinge, keys, etc), so I don't see how hitting it could fix it unless it's a temporary fix (such as a cold solder joint, loose connection, etc). If you have solder joint problems then the phone wants replacing. However, one thing I am certain of, is that hitting or banging your phone is liable to damage it, and there will be people out there who after reading this thread will lay their phone face down as instructed, and hit it phone hard enough to snap the "chin" off.

[CJ Chitwood]

Well, I don't think I advocated beating the phone up... I did mention that tapping the phone just right seemed to help. Then again, it may have been a coincidence that the act of turning the phone sideways to open the keyboard, then turning it over to tap it on the wrist, may have had a calibrating effect on the sensor, and the physical contact of the phone with the wrist had no beneficial effect at all.

I feel I know more about my phone now. If the HE sensor is completely unaffected by strong magnets, then I should be able to play with the phone for a bit and then get the same readings after playing with it as I did before. We'll see.

Also, one last question. If there exists no such material as to shield magnetic force, what does cause the magnets used in hard drives (and no doubt other applications) to be so directionally strengthened? I'm sincerely curious on this subject... I think I might just google it...

[extorian]

If there exists no such material as to shield magnetic force, what does cause the magnets used in hard drives (and no doubt other applications) to be so directionally strengthened?

Well, this isn't true. There are a number of materials that shield from magnetic fields and these are used all the time (especially around speakers, for example, to prevent them damaging old TVs). I believe any ferrous material will do this, but there are also some specialist non-ferrous materials such as http://www.lessemf.com/mag-shld.html

I think what the post you were referring to meant was that there is no such shielding between the magnets and the disk surface in a hard drive. This is because it's not needed there.

Yes - the magnets are extremely powerful. But they're polarised so the magnetic force is most powerful above and below their flat surface, not out of the ends of them. As the magnets lay flat inside the hard drive, the magnetic force is mostly directed towards adjacent casing. The magnetic force that is directed towards the disk is hence very weak.

Finally, to damage the data on the disk you need a powerful magnetic force that's extremely close (i.e. under a millimetre) from the surface of the disk, with the field directed directly at the surface. This arrangement is not present in a hard drive - the edge of the magnet (weak side) points towards the edge of the disk (not the top/bottom surface).

If the magnets were held flat a fraction of a millimetre flat above the disc's surface that would be a different story... but they're not.

[RueTheDay]

So has it been positively determined that magnetic latches do NOT cause any PERMANENT issues with the G1? InspectorGadget's post was pretty convincing.

Also, I have tested the magnetic latch on the MDA case I have with a pen knife - the magnetic attraction is strong on the outside of the case, but undetectable on the inside of the case. They must have some very good shielding material between the latch and the case.

[extorian]

Yes - my G1 is still fine. I've had a magnetic clasp case getting on for 2 months now, and my G1 is usually right next to a very strong magnet from it (Krussel Horizon S-Wide case).

Hall effect ICs are not affected permanently by strong magnetic fields - they're DESIGNED to measure them close up.

In the highly unlikely event that material inside your phone became magnetised then the IC will recalibrate itself within a few seconds anyway - just like it does with the relatively strong magnets already close to it in the microphone and speaker!

I use the compass feature frequently with GeoBeagle when Geocaching. It's spot on still.

One thing to note is that the compass is only reliable when the phone is face up with the keyboard closed. You are likely to get weird results if you stand up holding the phone upright with the screen facing towards your face. Some people mentioned in this thread weird results (spinning around etc). That's expected if the phone is not face up to the sky.

I don't know why having the keyboard open makes any difference, it's just something I read once, it may be an urban myth.

[CJ Chitwood]

I'm going to try one more time. When I last posted to this thread, I played with the phone and a magnet. Less than a day later, my compass AND accelerometer BOTH quit working 100% altogether. It HAS to be a coincidence, I'm sure, but it sure is annoying doing that hard reset.

So I'll try one more time tonight and see if/when they stop working again. Then again, it can't be a hardware issue if a hard reset cures it. Has to be software / driver.


Edit: FWIW, I believe Extorian et al. It's just one hell of a coincidence for the phone to quit working right after messing with a magnet near it.

[extorian]

For what it's worth, if I'd had your experience, I would be sceptical of the supposed safety of magnets around the G1 too. There's no harm in caution.