Speed Up Deodexing with JoelDroid Batch Deodexer

Android 5.0 Lollipop brings many under-the-hood changes like changing the default compiler … more

Top 5 Apps for 2014 + Top Xposed Mod of 2014 – XDA TV

Its that time of year where you look back and remember the things that happened … more

NVIDIA SHIELD Tablet Gets Android 5.0.1, OTA Available

The NVIDIA SHIELD Tablet is the latest Android-powered device released by famed GPU … more

FXP Team Delivers Lollipop to Various Xperia Devices!

From all of us here at XDA-Developers, we’d like to wish you Happy Holidays! If … more

Welcome to XDA

Search to go directly to your device's forum

Register an account

Unlock full posting privileges

Ask a question

No registration required
Post Reply

NFC Antenna (Back Cover) can be magnetized and will affect compass

OP chadrockey

8th January 2011, 10:38 PM   |  #1  
OP Junior Member
Flag Cleveland
Thanks Meter: 4
 
28 posts
Join Date:Joined: Apr 2009
More
So I've been noticing that my compass would always misbehave (in terms of accuracy, not stability a la Sky Maps). I would get a pretty large static error (30 to 40 degrees obviously not declination); rotations would not be consistent (IE, a 180 degree turn would yield 100 degrees change.); and the magnitude of raw measurements was not like that of the magnetometer I got from Sparkfun.

Turns out the neodymium magnets I had near my desk actually latched onto my phone and magnetized the NFC antenna. I tested this by removing the cover and putting the magnet near the antenna and it sticks. :P Without the cover on, the compass worked much better.

I've mostly demagnetized my NFC antenna now by doing some magnet sweeps and leaving it near the heater, but I've learned to keep the magnets away.

If anyone is having problems with the compass overall accuracy, removing the back cover may help.
Attached Thumbnails
Click image for larger version

Name:	IMG_20110108_163323.jpg
Views:	518
Size:	102.7 KB
ID:	484233  
The Following 2 Users Say Thank You to chadrockey For This Useful Post: [ View ]
9th January 2011, 02:15 AM   |  #2  
Senior Member
Flag Perth, WA
Thanks Meter: 254
 
1,223 posts
Join Date:Joined: Dec 2010
Donate to Me
More
Quote:
Originally Posted by chadrockey

Turns out the neodymium magnets I had near my desk actually latched onto my phone and magnetized the NFC antenna. I tested this by removing the cover and putting the magnet near the antenna and it sticks. :P Without the cover on, the compass worked much better.

I've mostly demagnetized my NFC antenna now by doing some magnet sweeps and leaving it near the heater, but I've learned to keep the magnets away.

Why did you have such strong magnets near your desk? lol

Quote:
Originally Posted by chadrockey

I've mostly demagnetized my NFC antenna now by doing some magnet sweeps and leaving it near the heater, but I've learned to keep the magnets away.

Phones + magnets = bad same as with hard drives, but I guess at least you don't loose files with magnets and phones that would suck...
9th January 2011, 02:26 AM   |  #3  
OP Junior Member
Flag Cleveland
Thanks Meter: 4
 
28 posts
Join Date:Joined: Apr 2009
More
I use them to test various things, such as magnetic interference on magnetometers in phones/compasses/inertial measurement systems. :P The magnets used to hold doors closed are very powerful and affect compass heading. Rare earth magnets are also extremely cool.

That's mostly a myth with the hard drives. Floppy disks/cassette tapes sure. I think it takes something like .2 to .5 Telsa to actually start affect hard drives. My largest magnet is only something like .1. In large spinning drives, they all contain a neodymium magnet in the center.

Mostly I was surprised that the NFC antenna could be imprinted by a magnetic field. I was getting a pretty significant field too. The change was something like 10 uT.

Sources:
http://www.pcworld.com/article/11657..._pc_myths.html
http://en.wikipedia.org/wiki/Neodymium_magnet
9th January 2011, 04:22 AM   |  #4  
Senior Member
Flag Perth, WA
Thanks Meter: 254
 
1,223 posts
Join Date:Joined: Dec 2010
Donate to Me
More
Quote:
Originally Posted by chadrockey

I use them to test various things, such as magnetic interference on magnetometers in phones/compasses/inertial measurement systems. :P The magnets used to hold doors closed are very powerful and affect compass heading. Rare earth magnets are also extremely cool.

That's mostly a myth with the hard drives. Floppy disks/cassette tapes sure. I think it takes something like .2 to .5 Telsa to actually start affect hard drives. My largest magnet is only something like .1. In large spinning drives, they all contain a neodymium magnet in the center.

I took apart several old hard drives and found those magnets, so I knew about it but they are exceptionally strong! the two magnets are near impossible to pull away from each other when stuck, you have to slide them I have since lost them though
28th September 2012, 04:37 AM   |  #5  
Senior Member
Thanks Meter: 147
 
623 posts
Join Date:Joined: Sep 2010
Thanks for the tip here! Removing the back cover does indeed bring my compass back to sanity. However, I have no idea how to demagnetize the NFC antenna. What are magnet sweeps? Any suggestions?
28th September 2012, 11:35 AM   |  #6  
Senior Member
Thanks Meter: 76
 
627 posts
Join Date:Joined: May 2010
More
Didn't saw this thread either.

Thanks will check it later if compass works fine without the back cover
1st October 2012, 02:47 AM   |  #7  
Senior Member
Thanks Meter: 76
 
627 posts
Join Date:Joined: May 2010
More
Tried without cover and it works ok!

Now need to find a way to de-magnetize thus damn cover :-\
1st October 2012, 04:02 PM   |  #8  
Senior Member
Thanks Meter: 147
 
623 posts
Join Date:Joined: Sep 2010
If you figure out how please let us know.
4th October 2012, 04:02 AM   |  #9  
jeremy112683's Avatar
Senior Member
Thanks Meter: 32
 
488 posts
Join Date:Joined: Jan 2011
Google how to demagnetize metal...


Sent from my Nexus S 4G using xda app-developers app

Post Reply Subscribe to Thread
Previous Thread Next Thread
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes