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Cfixer: Compass degausser or just more Snake Oil ?
1671 23 2018-4-3
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dorbot
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This question may require an informed response from a qualified DJI hardware representitive as it is vaugely technical.

Does anyone have any insight into the validity of the Cfixer degauss device for fixing your compass problems ?
Does the Phantom 4 pro or the phantom series in general have their own built in degauss function during calibration and / or startup?

I build a PC headtracking gadget called the EDTracker and it needs a well calibrated magnetometer for yaw drift compensation. It has a degauss function built into the magnetometer module which we call automatically on each startup.  
I was wondering if the Cfixer was just a con or something that might have some utility, and if phantoms have heir own built in degauss or not?

I also saw some videos where phantom 3 users were moving a magnet round the compass in the landing gear to degauss it but that sounds like a recipe for breaking an otherwise good magnetometer disaster to me..............

Anyone have any thoughts?
I'm going with snake oil for now.........






2018-4-3
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Geebax
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Doesn't it come from Russia?
That should tell you.

Seriously, the web site blurb starts off with "How many times have you seen the message 'Compass Error", Anyone who knows enough about the way the compass works will tell you that when that error comes up, degaussing the compass module is not going to solve the problem. More to the point, the compass module usually uses a MEMS Magnetic field sensor, and there is nothing magnetic in one that requires degaussing.

In fact, try degaussing a normal needle compass and see what happens! Clue: the compass will fail to work completely.


2018-4-3
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Nigel_
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Well, if you follow their instructions for using it then you will indeed fix any compass error

Not because of their device, but because the last step in their instructions is to calibrate the compass!

However, as is often said on this forum, if you are launching from on top of your car as in their example, or from any other location that results in a compass error - do not take off, instead power down the aircraft and move it to somewhere else which does not give a compass error, because if the compass error is caused by the location rather than the aircraft, as they nearly all are, then recalibrating the compass is going to result in a crash!
2018-4-4
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ALABAMA
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You're right......snake oil for sure.
2018-4-4
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Labroides
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Too many people think a compass error is something wrong with the compass which must be "fixed"
When it actually is a perfectly good compass that is warning that it has detected a problem.
2018-4-4
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Bashy
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Nigel_ Posted at 2018-4-4 15:13
Well, if you follow their instructions for using it then you will indeed fix any compass error

Not because of their device, but because the last step in their instructions is to calibrate the compass!

Bear in mind that that compass error may not show until after  take off, and truthfully now, who is actually looking at the screen during take off, nu uh, not me, i am watching the take off with my very own live  view, and i am 99% sure that i didnt hear  any warning saying compass error, so on some occasions there is no way of knowing until its too late, yes, ok, so not taking off from my cars sunroof would have mitigated the risk of an error but hey, stupid me, stupid does, and i honestly thought the glass would be ok after all, it is half the roof, dont grill me, already charred..... but, in the time from the activation of take off, to the error, was literally seconds, it recorded the error at 0.3m and it was in that moment that it then quickly shot off to the left, far too late to respond to the error, by this time you are responding to the infamous Fly Away.
2018-4-4
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ArcticPhoto
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The cfixer worked for me. Ever since my P4A+ was brand new, I have been getting the compass error message all the time and everywhere I have been flying. Calibration and new firmware did not help. I used the cfixer, calibrated the compass and took off on a location I have been before (with lots of compass errors, drifting etc). But now, after degaussing and calibration, it behaved perfect! I emptied two batteries without a single error message, that was unthinkable before. So it definitely helped. My guess is that the P4A somehow has been stored close to strong magnets, maybe some speakers in the electronics warehouse I bought it from.
I had almost given up my P4A and was about to return it to DJI, but now it seems reliable, and I fly much more relaxed
2018-4-13
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Nigel_
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ArcticPhoto Posted at 2018-4-13 05:40
The cfixer worked for me. Ever since my P4A+ was brand new, I have been getting the compass error message all the time and everywhere I have been flying. Calibration and new firmware did not help. I used the cfixer, calibrated the compass and took off on a location I have been before (with lots of compass errors, drifting etc). But now, after degaussing and calibration, it behaved perfect! I emptied two batteries without a single error message, that was unthinkable before. So it definitely helped. My guess is that the P4A somehow has been stored close to strong magnets, maybe some speakers in the electronics warehouse I bought it from.
I had almost given up my P4A and was about to return it to DJI, but now it seems reliable, and I fly much more relaxed

Given that you fly in the Arctic where the Earth's magnetic field is very weak, it is not surprising that you frequently get compass issues.  Maybe you have been lucky with solar and magnetic activity since you got your cfixer and things will soon be back to normal soon?  

I would want to hear the experience of people who fly south of the arctic circle before believing in the snake oil, and also from people who have more than 1 post on the forum!

2018-4-13
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ArcticPhoto
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Nigel_ Posted at 2018-4-13 13:51
Given that you fly in the Arctic where the Earth's magnetic field is very weak, it is not surprising that you frequently get compass issues.  Maybe you have been lucky with solar and magnetic activity since you got your cfixer and things will soon be back to normal soon?  

I would want to hear the experience of people who fly south of the arctic circle before believing in the snake oil, and also from people who have more than 1 post on the forum!

The cfixer is nothing more than a degausser, so the questions are
1. If a Phantom is stored close to strong magnets (speakers for example), will that affect the compasses so that they don't work properly?
2. Degaussing removes unwanted magnetism, so if the compasses in the Phantom have been exposed to strong magnets, degaussing should reset them back to normal. Or am I totally wrong here?
2018-4-14
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Aardvark
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Nigel_ Posted at 2018-4-13 13:51
Given that you fly in the Arctic where the Earth's magnetic field is very weak, it is not surprising that you frequently get compass issues.  Maybe you have been lucky with solar and magnetic activity since you got your cfixer and things will soon be back to normal soon?  

I would want to hear the experience of people who fly south of the arctic circle before believing in the snake oil, and also from people who have more than 1 post on the forum!


"Given that you fly in the Arctic where the Earth's magnetic field is very weak"


The magnetic field is very strong near the poles of the magnet (Earth), however it becomes unreliable as the direction of the field changes as it converges (changing from horizontal to vertical).

A nice article (of which there are many) Here

On page 54 (note 6) of the manual DJI states that the Phantom cannot be used in the Polar regions.

I would agree that there should be nothing to degauss on the Phantom. Last time (and only time) I had anything degaussed it was a 26" CRT tube, where the TV had been sitting right next to a beast of a speaker magnet.
2018-4-14
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KedDK
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ArcticPhoto Posted at 2018-4-14 01:05
The cfixer is nothing more than a degausser, so the questions are
1. If a Phantom is stored close to strong magnets (speakers for example), will that affect the compasses so that they don't work properly?
2. Degaussing removes unwanted magnetism, so if the compasses in the Phantom have been exposed to strong magnets, degaussing should reset them back to normal. Or am I totally wrong here?

I find it hard to believe that anything in the plastic legs where the compass is placed would build up any magnetic field that would need degaussing.
But it should be easy to test, just wave around the legs when powered off with a good old compass and see if the needle get attracted in a specific direction on the legs.
2018-4-14
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KedDK
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Aardvark Posted at 2018-4-14 01:53
"Given that you fly in the Arctic where the Earth's magnetic field is very weak"

The magnetic field is very strong near the poles of the magnet (Earth), however it becomes unreliable as the direction of the field changes as it converges (changing from horizontal to vertical).

Just the other day our news had a story about the magnetic north is moving from Canada toward Siberia at a speed of 50-60km/y. Nothing new that it is moving, i even leaned that in school many years ago but the news was that the movement is accelerating  in speed.
I would think that the south pole move the same but the news was only talking about the north.

Perhaps a compass calibration once a year is the way to go.
2018-4-14
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ArcticPhoto
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Aardvark Posted at 2018-4-14 01:53
"Given that you fly in the Arctic where the Earth's magnetic field is very weak"

The magnetic field is very strong near the poles of the magnet (Earth), however it becomes unreliable as the direction of the field changes as it converges (changing from horizontal to vertical).

"On page 54 (note 6) of the manual DJI states that the Phantom cannot be used in the Polar regions."
Magnetic compasses do not work reliably on the north pole, so I guess a Phantom there would be very confused. I live in an Arctic region, but ordinary compasses work well here, as long as we take the declination into consideration.
I asked DJI to clarify what they mean with polar regions, and here is the response: "With regards to your concern, polar regions are the areas with severe weather conditions like wind exceeding to 10m/s, snow, rain and smog. As we do not recommend to our customers to use their aircraft in such weather condition."
Nothing about compass problems.  People are flying Phantoms on Svalbard without problems, and that is much closer to the North Pole than I am.
2018-4-14
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Nigel_
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ArcticPhoto Posted at 2018-4-14 06:46
People are flying Phantoms on Svalbard without problems, and that is much closer to the North Pole than I am.

No problem on Svalbard, the big problems are North West Greenland and North East Canada, sometimes some issues in North East Alaska.
2018-4-14
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Nigel_
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KedDK Posted at 2018-4-14 02:16
Just the other day our news had a story about the magnetic north is moving from Canada toward Siberia at a speed of 50-60km/y. Nothing new that it is moving, i even leaned that in school many years ago but the news was that the movement is accelerating  in speed.
I would think that the south pole move the same but the news was only talking about the north.

The North and South poles both move around, but are not really connected in the way that a bar magnet north and south are, they move independently, except when the North pole moves down to Antarctica and the South pole comes north, which is currently overdue to happen ... don't know if that would confuse our Phantoms or not?
2018-4-14
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Nigel_
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Aardvark Posted at 2018-4-14 01:53
The magnetic field is very strong near the poles of the magnet (Earth), however it becomes unreliable as the direction of the field changes as it converges (changing from horizontal to vertical).


I think the problem that causes Phantoms to go into atti mode near the magnetic poles is due to the horizontal component of the Earth's magnetic field being very weak near the poles, you are correct that the vertical component becomes strong.
2018-4-14
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Nigel_
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ArcticPhoto Posted at 2018-4-14 01:05
1. If a Phantom is stored close to strong magnets (speakers for example), will that affect the compasses so that they don't work properly?
2. Degaussing removes unwanted magnetism, so if the compasses in the Phantom have been exposed to strong magnets, degaussing should reset them back to normal. Or am I totally wrong here?

Most of the Phantom is made out of non-magnetic materials, plastic, magnesium alloy, copper etc.
The motors contain large permanent magnets which are probably unaffected by being close to other magnets.
Which just leaves a few screws, motor axles and the like which could be magnetized but I doubt that would have much affect on the compasses.
As far as I know the compasses themselves can not be affected.

So any effect will be very minor and doing a compass calibration should completely cancel it, and so degaussing is definitely not required.
2018-4-14
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Geebax
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ArcticPhoto Posted at 2018-4-14 01:05
The cfixer is nothing more than a degausser, so the questions are
1. If a Phantom is stored close to strong magnets (speakers for example), will that affect the compasses so that they don't work properly?
2. Degaussing removes unwanted magnetism, so if the compasses in the Phantom have been exposed to strong magnets, degaussing should reset them back to normal. Or am I totally wrong here?

'2. Degaussing removes unwanted magnetism, so if the compasses in the Phantom have been exposed to strong magnets, degaussing should reset them back to normal. Or am I totally wrong here?'

There is nothing magnetic in the solid state compass device, so a degauser will not have any effect at all on it.
2018-4-14
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ArcticPhoto
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Geebax Posted at 2018-4-14 15:46
'2. Degaussing removes unwanted magnetism, so if the compasses in the Phantom have been exposed to strong magnets, degaussing should reset them back to normal. Or am I totally wrong here?'

There is nothing magnetic in the solid state compass device, so a degauser will not have any effect at all on it.

OK, I do not know how the Phantom compass work. But ever since my P4A was new, I got compass errors all the time while flying. Always, no matter where I was flying. Calibrating did no difference. Then I degaussed the compasses, and as I said, I flew almost two batteries without a single error. That has never happened before.  This was on a location where I have flown before, with errors. Coincidence? I don't know. I need to do more testing and flying before concluding. But if I now can fly without compass error message I must conclude that the degaussing actually helped. No other variables have changed (firmware, location etc).
2018-4-15
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Aardvark
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ArcticPhoto Posted at 2018-4-15 00:36
OK, I do not know how the Phantom compass work. But ever since my P4A was new, I got compass errors all the time while flying. Always, no matter where I was flying. Calibrating did no difference. Then I degaussed the compasses, and as I said, I flew almost two batteries without a single error. That has never happened before.  This was on a location where I have flown before, with errors. Coincidence? I don't know. I need to do more testing and flying before concluding. But if I now can fly without compass error message I must conclude that the degaussing actually helped. No other variables have changed (firmware, location etc).

"I don't know. I need to do more testing and flying before concluding. But if I now can fly without compass error message I must conclude that the degaussing actually helped."

You've just contradicted yourself there. It is extremely unlikely that the degausser actually did anything apart from lighten your wallet a bit, given that there is nothing to degauss.
2018-4-15
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ArcticPhoto
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Aardvark Posted at 2018-4-15 04:26
"I don't know. I need to do more testing and flying before concluding. But if I now can fly without compass error message I must conclude that the degaussing actually helped."

You've just contradicted yourself there. It is extremely unlikely that the degausser actually did anything apart from lighten your wallet a bit, given that there is nothing to degauss.

"You've just contradicted yourself there."

I don't think so. As I said, I flew for around 40 minutes after degaussing, with no error message. Before degaussing I got compass error all the time, about every 30-40 seconds, it lasted for 10-20 seconds until it returned to P-GPS mode. This was in the same location, no other changes to AC or RC.
Flying for so long time with no errors was unthinkable before degaussing. Something has changed that made the error message disappear, I need to fly more in different locations to see if it's a permanent solution.
2018-4-15
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Geebax
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ArcticPhoto Posted at 2018-4-15 04:48
"You've just contradicted yourself there."

I don't think so. As I said, I flew for around 40 minutes after degaussing, with no error message. Before degaussing I got compass error all the time, about every 30-40 seconds, it lasted for 10-20 seconds until it returned to P-GPS mode. This was in the same location, no other changes to AC or RC.

In the instructions for using the degausser, the last stage is to calibrate the compass. That is more likely to solve the problem than the degausser.
2018-4-15
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Most_Brazil
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Hi.
My friend works in DJI repair service and he said that Phantom 4 and 4pro compasses can be magnetised. You can try magnetise them yourself: put magnet to the Ph4p compass (in the center of the legs), them remove magnet. And you can see in Compass state screen how your green status become yellow and red.
2018-4-29
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Bashy
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I know this is old but sommat came up on the DJI FB Page, and this was mentioned


2018-7-6
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