Discussions

HELP! Compass calibration.

Posted by Tamás L. Páll (Tom) on December 22, 2014 at 1:09pm

Hi all,

I need your opinion on some calibration data I got from the last pixhawk I have received:

COMPASS_OFS_X,-102
COMPASS_OFS_Y,-4
COMPASS_OFS_Z,267
COMPASS_OFS2_X,84
COMPASS_OFS2_Y,-325
COMPASS_OFS2_Z,-312

in the 20 minutes I was working on something else I had several "BAD COMPASS HEALTH" notification. 

I also have an APM 2.6 and the same type of compass(UBlox)

the calibration data of the APM is

COMPASS_OFS_X,-56.83081
COMPASS_OFS_Y,-4.790942
COMPASS_OFS_Z,-19.75378

Calibration has been done in the same room under identical conditions.

Can you please tell me if this Pixhawk and Ublox is safe to use or not?

Thanks in advance!

Tom

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Replies

  • Louis Wise February 1, 2015 at 6:37am

    I've found that AMP Planner 2.0 on my Mac doesn't do a good cal. I switched to Mission Planner on a Windows machine and got a better cal after upgrading to 3.2 on my Pixhawk. 

    Louis

  • Gustav Kuhn December 23, 2014 at 6:10am

    Indoors or outdoors?

    Any RF transmitting stuff near the actual GPS ?

    Pictures of your installation ?

    The only thing "Safe" is to sit in your favourite chair, and drink purified water :-)

    • Tamás L. Páll (Tom) > Gustav Kuhn December 23, 2014 at 10:49pm

      Testing has been done indoors

      Pic attached.

      with all the junk in orbit my favourite chair is not safe at all :-)

      IMG_0520.JPG

      • Moderator
        Graham Dyer > Tamás L. Páll (Tom) December 24, 2014 at 5:57am

        Compass calibration should only be done when installed on your airframe just before the first flight as it takes into account all the metal (screws, wire, etc) on the airframe and it's location relative to those metal bits. If you do it now it will have to be done again anyway when it's ready to fly. It should always be done outside away from cars, metal roofs, railings, etc. Apparently even underground pipes and cables can have a small effect. 

        • Tamás L. Páll (Tom) > Graham Dyer December 25, 2014 at 10:27pm

          Graham,

          I will definitely do a re-calibration once it is in the air-frame, if I ever put it in an air-frame. I don't want to wreck my Maja, and my fx-79 is pretty unstable since the crash with the Pixhawk. 

          I am unsure if I should try this at all or should I just send it back to the supplier.This is the second Pixhawk with compass problems that I am getting from the same supplier. The first one crashed 2.2km from takeoff location and the entire flight looked like the flight of a drunk duck. 

          Question: 

          Is it possible for an EM/magnetic field to have a permanent/long lasting effect on the magnetometer? 

          Which FW version you suggest to use? 3.0.3 or 3.2?

      • Greg > Tamás L. Páll (Tom) December 24, 2014 at 5:40am

        The physical proximity of all that to your compass may be part of your issue.   Mount that gear up on your copter and get that compass separated as best you can from the rest and see if things get better.

  • Tamás L. Páll (Tom) December 23, 2014 at 1:51am
    Thanks Greg! I am a little worried about the "Bad compass health" notification. Is that normal fron 10-10 minutes?
    • Greg > Tamás L. Páll (Tom) December 23, 2014 at 5:16am

      Have you tried recalibrating.

  • Greg December 22, 2014 at 3:32pm

    I had Z of over 550 until getting a replacement.  I manually set it down to -499 and flew just fine, although I didn't entirely trust it. 

    I doubt you will have flight problems with those values if they are repeatably in the same range.

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