How does the Series 5’s compass work?

5l4PN1X

macrumors newbie
Original poster
Jan 21, 2020
10
2
Ever since it was announced, I’ve been wondering how the compass in the Series 5 is able to work considering the magnet built into the watch for sticking to the charging puck. I would assume that it would interfere with it. The only mention of it I've ever come across is here, in iFixit's teardown, where he says "...the built-in compass is new, and supposedly uses a very tiny gyroscope (and presumably some very fast math) to compensate for interference from the magnets inside the watch." Now I'm not an engineer or anything, but it's not apparent to me how a gyroscope would help in this situation. Also, as an aside, did previous models of Apple Watch not have a gyroscope?

It has also occurred to me that because the position of the magnet in the watch is fixed, the earth's magnetic field could theoretically still be detected through that of the magnet, but are there really magnetometers with the precision, etc. to do that that can be incorporated into an Apple Watch without raising the price?

Again, I'm no expert, but I do feel like I'm missing something.
 

5l4PN1X

macrumors newbie
Original poster
Jan 21, 2020
10
2
That doesn’t answer my question. Did you read the post?
 

SRLMJ23

macrumors 68020
Jul 11, 2008
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Central New York
I do not know how they get it to work, but it does work absolutely correct.

I can take my real compass and compare it, and it is spot on, so that math or whatever it is doing to compensate for possible interference is working.

Edit: Also, yes, the article above me from Wikipedia does essentially answer your question, in my opinion.

:apple:
 

5l4PN1X

macrumors newbie
Original poster
Jan 21, 2020
10
2
It doesn't explain how it avoids interference from the adjacent magnet. Apple has admitted that bands with magnets in them will affect it, and experiments I've conducted with similar strength magnets at similar distances clearly do. Are you saying that they just are in fact sensitive enough to register the earth's magnetic field on top of the magnet's? If that's the case, then I don't understand what a gyroscope would have to do with this issue of the embedded magnet.
 

Significant1

macrumors 6502a
Dec 20, 2014
795
252
Are you sure the magnets are not only in the charger? It should be easy to check.

I don't understand what the purpose of having magnets in the watch should archive, when orientation of the charger doesn't matter.

Before s5 I thought the reason Apple watch didn't have compass was the metal casing.
 

5l4PN1X

macrumors newbie
Original poster
Jan 21, 2020
10
2
Yes. I have checked, and there is in fact a magnet in both the charger and the Series 5 itself. Unmagnetized pieces of steel, etc. stick to the back of the watch. I've tested this with various items. That this isn't the case was my first thought too until I was able to check for myself.
 

SRLMJ23

macrumors 68020
Jul 11, 2008
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Best explanation I could find:


Yes, certain magnetic bands will most likely mess with the compass, but if you don’t have a magnetic band, it is safe to say in this instance that “it just works.”

:apple:
 

5l4PN1X

macrumors newbie
Original poster
Jan 21, 2020
10
2
Right. What I'm asking here is why the same is not true of the magnet inside the watch that holds it on the charger. It's even closer to the magnetometer than ones in a band would be. Like that article says, Apple can't change the laws of physics. A magnetic field is a magnetic field.

I realize not everyone is as curious about this as me and that most people are content to say "it just works", but I'd like to know how. I guess I'm just weird.
 

matrix07

macrumors 603
Jun 24, 2010
5,259
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Right. What I'm asking here is why the same is not true of the magnet inside the watch that holds it on the charger. It's even closer to the magnetometer than ones in a band would be. Like that article says, Apple can't change the laws of physics. A magnetic field is a magnetic field.

I realize not everyone is as curious about this as me and that most people are content to say "it just works", but I'd like to know how. I guess I'm just weird.
Seems to me like you’ve already answered yourself from the 1st post here

and presumably some very fast math) to compensate for interference from the magnets inside the watch."
Whatever is inside the watch Apple already knows about it and already taken to account while outside changes (like bands) Apple couldn’t possibly compensate for it since they won’t know when or what you’ll use?
 

5l4PN1X

macrumors newbie
Original poster
Jan 21, 2020
10
2
Yes. That's currently my best guess. I'm just shocked that a magnetometer inexpensive enough to be added to the Apple Watch is capable of registering the earth's magnetic field against one that is so much stronger, and iFixit/Craig Lloyd's mention of the issue being solved with a gyroscope also has me confused. I was just hoping that someone here would know more than me and be able to either confirm the former or clarify the latter.
 

oeagleo

macrumors 6502a
Feb 5, 2016
653
368
West Jordan, Utah
Has anyone thought that for Apple, it's easy to offset the field of the INTERNAL magnets; they're stable, they don't change, and they don't come and go. Magnets in watch bands, or other devices may be there, and may come and go with the changing of the bands, etc, and the field isn't stable. Easy to stack BB's when there's no wind, add some wind, and it all goes to sh**.. Just my thinking of "how it works', or why it works sometimes.
 

SRLMJ23

macrumors 68020
Jul 11, 2008
2,119
1,081
Central New York
Right. What I'm asking here is why the same is not true of the magnet inside the watch that holds it on the charger. It's even closer to the magnetometer than ones in a band would be. Like that article says, Apple can't change the laws of physics. A magnetic field is a magnetic field.

I realize not everyone is as curious about this as me and that most people are content to say "it just works", but I'd like to know how. I guess I'm just weird.

I do not think you are weird for wanting to know how Apple compensates for internal magnet. I mean, I am a big tech guy, build my own computers and what not...I like to know and see how things work.

In this case, since none of us here designed the watch, we just have to come up with a good educated guess aka hypothesis. My money is on the S5 System in Package (SiP), doing that really quick math that was mentioned earlier. That is the only way I see how it can work so precise, even with a magnet in it, the hardware and software (mainly the hardware - SiP) work together to overcome that issue.

Best I can guess right now, as I am exhausted!

I still absolutely love my Series 5!

Edit: I just took a quick look on Apple's website and it says this about the compass:

Screen Shot 2020-02-19 at 12.35.43 AM.png


Not sure if that helps or not, but it seems it does some sort of conversion from Magnetic North, too True North. I know you can change that is settings if you want, but that's really all I have for tonight!

:apple:
 
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5l4PN1X

macrumors newbie
Original poster
Jan 21, 2020
10
2
Has anyone thought that for Apple, it's easy to offset the field of the INTERNAL magnets; they're stable, they don't change, and they don't come and go. Magnets in watch bands, or other devices may be there, and may come and go with the changing of the bands, etc, and the field isn't stable. Easy to stack BB's when there's no wind, add some wind, and it all goes to sh**.. Just my thinking of "how it works', or why it works sometimes.
Yes. I mentioned this in my original post as well as post #13. Like I said, it would just be impressive to me if this magnetometer could accurately measure changes that small in a net magnetic field as strong as this would be, and again, what of this talk of gyroscopes?
- - Post merged: - -

I do not think you are weird for wanting to know how Apple compensates for internal magnet. I mean, I am a big tech guy, build my own computers and what not...I like to know and see how things work.

In this case, since none of us here designed the watch, we just have to come up with a good educated guess aka hypothesis. My money is on the S5 System in Package (SiP), doing that really quick math that was mentioned earlier. That is the only way I see how it can work so precise, even with a magnet in it, the hardware and software (mainly the hardware - SiP) work together to overcome that issue.

Best I can guess right now, as I am exhausted!

I still absolutely love my Series 5!

:apple:
The issue is I can't imagine, even as a vague concept, what math there would be to be done to accomplish this.

Edit: And yes, I understand that it converts the magnetic north that it detects to true north using the World Magnetic Model. Calculations accounting for magnetic declination in that way make perfect sense to me. What I'm talking about is how it obtains the magnetic north reading in the first place.
 
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SRLMJ23

macrumors 68020
Jul 11, 2008
2,119
1,081
Central New York
Yes. I mentioned this in my original post as well as post #13. Like I said, it would just be impressive to me if this magnetometer could accurately measure changes that small in a net magnetic field as strong as this would be, and again, what of this talk of gyroscopes?
- - Post merged: - -


The issue is I can't imagine, even as a vague concept, what math there would be to be done to accomplish this.
Apparently that gyroscope is very important in how the SiP and Magnetometer eventually come up with the correct location.

Also, I was just thinking, maybe the GPS chip helps out in some way?

This is where it gets to the point where we are just coming up with our best hypothesis.

I guarantee you someone(s) on this forum knows how this works, you just have to hope that they see the thread and hop in and explain!

:apple:
 
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