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  1.    #1  
    Just curious,
    The Pre 3 DOES have a built in Compass (Magnetometer), just like many other phones today.
    However, the touchstone does in fact also have a strong magnet that 'clamps' the phone in place whilst charging.

    I'm wondering, would the strong magnetic field over time, 'corrupt' & strongly magnetise the pre 3's built in Magnetometer, thus ruining it?
    A) That's not how they work and it'll be fine,
    B) The designers thought of that, and the phone will be OK long term,
    C) The phone's Magnetometer WILL eventually get f*cked, & the designers deliberately didn't care, because it's a consumer item, that's not meant to last...?

    If C, should we all STOP using our touchstone's & revert to charging via USB only?

    Just curious....
  2. #2  
    That's been a debate when folks looked at TouchStoning other devices. Some people have advocated installing magnets in the TS plate to make it stick better for heavier phones. I warned that this would for sure render the compass useless. As for the physics of it, the standard Palm back plate doesn't actually have magnets. The strong magnets are in the base, the cover has four magnetic (but unmagnetized) metal slugs.

    So just now I installed Jason's Quick Compass app (nice, Jason!). My phone's many months old, I use a Touchstone almost daily, and still it immediately got an accurate heading and was very smooth and responsive. Very useful compass, actually! But then again, it hasn't seen a Touchstone for a couple of days. (I charge by the port at home, TS at work.)

    This tells me that whatever effect the Touchstone has, it at least doesn't appear to be permanent.

    Then I put it near a refrigerator magnet. Of course that messes it up, but when I remove the magnet it's normal again.

    Then I put it on an active Touchstone. It goes crazy! Two things mess with it. 1) TouchStone field is quickly alternating, not "DC." 2) The magnets that hold it are strong steady fields.

    Okay... then take it off. Now the compass is stuck. The likely reason is the hysteresis in the magnetic disks. The "magnetic memory" of ferromagnets. Apparently the slugs are now magnetized and attracting the compass point. Either that or the compass itself is placed in such a way that it picks up its own magnetization.

    The latter seems unlikely given how perfectly it was working just before I put it on the Touchstone though.

    Anyway, go nab Quick Compass from the Catalog and have a look. At least in the few minutes it took to write this post, the compass is still stuck after being on the TS!
  3. #3  
    Oh, wowzers. I just removed the back plate with Quick Compass running and it's still stuck. So what's going on?

    THEN I also recall Rod saying something about some soft calibrations/tracking for the compass when he was TSing his Nexus. So let's see, if I perform a device reboot...

    Yup! Now it's back to normal even with the cover on. So it seems the TS can scramble something or other, but a reboot seems to fix it. So it's likely not a strong enough physical magnetization to permanently cripple the compass, just enough to confuse the digital sensor temporarily.
  4.    #4  
    Hi ananimus,
    Very kind of you to run this little experiment. Personally I've not seen any permanent problem with the built in compass, even though I've been charging my Pre 3 on the TS ever since i got it. All i seem to have to do is give the phone a gentle figure of 8 shake.
    One thing i have noticed about my built in compass sensor, it is very fussy about being kept 'level' ...(similar to a real compass i guess?) ... But when level and placed on a surface, it does seem quite accurate.
    Best
    Al
  5. #5  
    Mine wasn't quite that twitchy. It's better level, but still seems pretty accurate when only mostly level. At any rate, yeah. It's still just a compass at heart so level's good.

    I've never really played with it before, but Quick Compass might be handy while walking new streets. She's a fine compass!
  6. #6  
    Quote Originally Posted by ananimus View Post
    Oh, wowzers. I just removed the back plate with Quick Compass running and it's still stuck. So what's going on?

    THEN I also recall Rod saying something about some soft calibrations/tracking for the compass when he was TSing his Nexus. So let's see, if I perform a device reboot...

    Yup! Now it's back to normal even with the cover on. So it seems the TS can scramble something or other, but a reboot seems to fix it. So it's likely not a strong enough physical magnetization to permanently cripple the compass, just enough to confuse the digital sensor temporarily.
    That, and if it ever gets stuck, try doing figure 8s with the phone. Actually I found that trick from several Android compass apps, they actually tell you to do that to "calibrate" it.
    Palm IIIc -> Sony CLIÉ T650C -> Sony TJ-37 -> Palm TX -> Palm Centro -> Palm Pre Bell -> Palm Pre Plus Bell/Verizon Hybrid -> HP Veer -> HP Pre 3 NA -> BlackBerry Classic -> BlackBerry Priv

    It's a Late Goodbye, such a Late Goodbye.

    Need OEM Palm Pre parts? See here

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