Compass interference issues

ArduCopter Copter 4.4
1

I have put the propellers such that quad pushes itself down. I then armed the motors in stabilize mode and increased throttle to 60%. I also moved the throttle stick up and down quickly to get surge of current. During this I was checking my total magnetic field reading in the status of mission planner which did not vary by more than 50 mGauss.
Also EKF variance was less than 0.5 all times as seen in HUD.
But when I do compass-mot calibration in mission planner i see huge interference of 70-80% at 40% throttle.
If there is interference why does it not seen in the first case.
I did a small test on auto mode as well, log attached below.
The EKF normalized innovation does not seem to cross 0.5
Log

Can you please look at the compass logs here and share some insights?

2

No point in doing that, old stuff. Use Magfit.

1 Like
3

Edit: Don’t use these values after all…Not yet at least. See more below.

Ran Magfit on the log file:

COMPASS_OFS_X -83
COMPASS_OFS_Y 13
COMPASS_OFS_Z 44
COMPASS_DIA_X 1.200
COMPASS_DIA_Y 1.200
COMPASS_DIA_Z 0.877
COMPASS_ODI_X -0.022
COMPASS_ODI_Y 0.048
COMPASS_ODI_Z 0.094
COMPASS_MOT_X -2.304
COMPASS_MOT_Y -7.267
COMPASS_MOT_Z 10.000
COMPASS_SCALE 1.00
COMPASS_MOTCT 2
4

Z is at max so that’s a problem.

5

Agreed. Since I posted that I’ve been looking closer at the graphs and something doesn’t seem right. There’s something else going on here.

6

Yea, this looks fairly awful:

Mag THo
Mag THo3388Ă—1128 187 KB

I don’t suppose any “fit” will work well. Li-Ion battery?

@Brianoconner At least update to current Stable and work from there.

7

BAT.Volt_BAT.Curr
BAT.Volt_BAT.Curr1200Ă—600 109 KB

Seems we’re chasing the same idea.

@Brianoconner Is this LiPo or LiIon?

8

@dkemxr @Allister Thank you for your replies.

This is Li-ion battery, 4s.
When i run magfit for this same flight I donot get any values for compass_dia_ and compass_odi_. You are able to get these values as well.

I am using mozilla firefox web browser for magfit web tool.
Also I am not able to check boxes of “offsets and scale”, “offsets and iron boxes” in magfit.

9

I ran magfit in MavExplorer, so I was able to get those values. I noticed the same as you on the web tools.

Li-Ion batteries can be known for their interference. Is there anything you can do to get it further away from the compass?

10

This is small quad. I cannot put the compass further away from battery. The distance is 4 cm now.
Can you please tell some other way to arrest this magnetic interference?

11

Some people have had luck with shielding but I’ve never had to use it so I can’t offer much help here.

Have a read of this:

1 Like
12

Not much you can do on a small quad. I changed to a Lipo on a small craft with the same problem.

1 Like