Welcome to PhantomPilots.com

Sign up for a weekly email of the latest drone news & information

IMU calibration issue on brand new P3Pro...

Discussion in 'Pro/Adv Discussion' started by Jtrjr, Mar 19, 2016.

  1. Jtrjr

    Joined:
    Mar 28, 2015
    Messages:
    444
    Likes Received:
    277
    Location:
    South Dakota
    (I already posted this on the "other" board but thought it was important enough to post it here as well. I did a search here and on the other board trying to find out what I should do if the compass mod value in the advanced IMU calibration was over the acceptable range and couldn't find anything but degaussing.)


    I spent many hours today trying to properly set-up my new P3Pro. This is my 3rd Phantom, a P2V+ and two P3Pro's. I fly a lot and have quite a bit of experience with these birds. I'm pretty thorough and careful with my birds and take my time making sure they're set-up properly before they ever hit the air. As part of the initial set-up I think it's wise and prudent to do an advanced IMU calibration, a gimbal/camera calibration, an RC calibration and a good compass calibration. I've done all of these functions many times before so it's no big deal.

    Today I received a new P3Pro. I did as I always do and carefully unboxed everything, got all of my numbers and documents photographed and in order. I charged my RC and new battery. Once the charging was completed, I fired up everything and registered the bird with DJI. Checked all of the basic settings and changed them to my normal preferences. I figured I'd wait until the wife and dogs went to bed and then I'd do the calibrations so there wouldn't be any movement.

    It's nice and cold out (27F) so I figured I could get a good cold IMU cal first. I left the bird outside (minus the battery and SD card) for about a half an hour and set up my perfectly level, wood table in the center of a large room with no chance of interference. I brought the cold bird in, set it up on the table, fired up my Tablet and RC and then the bird. I went directly into the IMU calibration screen and noticed the compass mod was floating around 1,920 to 2,100 (way higher than the norm of 1,500-1,800) and hit the cal button. During the cal the numbers stayed in that unacceptable range. Cal completed at about 1,950, no good. The other mod numbers were good. I figured I'd just give it another go. Half an hour outside and back at it, same result. I started searching the threads and couldn't really find much on it.

    Long story a little bit shorter, I did it another couple of times then got another P3Pro to check it (maybe the environment was somehow screwed up?). I fired up the other P3 and it checked out good at about 1,550. I figured I'd try it one more time and if I couldn't get it I'd get it picked up by Amazon Prime (you've gotta love Amazon Prime!) in the morning. No good again, same result. As a last ditch effort I figured I'd go ahead and do a regular compass cal. Got a good compass cal, went into the IMU screen and bingo! Mod value is now around 1,580! Shut her down, put her back outside to let it get cold, brought it in, did the cal and all is good at about 1,540. Did the rest of my set-up with no further issues.

    The moral of the story, if your numbers are off, do a compass cal before you do the advanced IMU cal or you could be the next one up until 3:00am trying to get it done! Hope it helps someone in the future.

    Jerry
     
    bunkphenomenon likes this.
  2. Quadcopterpilot

    Joined:
    Nov 25, 2015
    Messages:
    260
    Likes Received:
    67
    Location:
    Grimsby, Ontario, Canada
    Good to know, thanks
     
  3. Oso

    Oso

    Joined:
    May 19, 2015
    Messages:
    2,526
    Likes Received:
    1,477
    Location:
    Sacramento CA
    I'm curious. Were you expecting an IMU cal to also calibrate your compass mod numbers into the normal range or am I misunderstanding your post?
     
  4. Erroll

    Joined:
    May 15, 2015
    Messages:
    501
    Likes Received:
    212
    Location:
    South Africa
    That is what I also understood from his post.
     
    Oso likes this.
  5. eaglegoaltender

    Joined:
    Jan 13, 2016
    Messages:
    741
    Likes Received:
    273
    That's great info to know about and I am sure it will help out others............thank you for that Jtrjr

    Sounds like you do like your "birds" and are a careful and responsible pilot!

    Yikes.....what's so "nice" about that --- LOL.
     
  6. rockydog

    Joined:
    May 25, 2015
    Messages:
    881
    Likes Received:
    248
    Location:
    London UK
    As @Oso and@Erroll are intimating above, it sounds as though you are expecting an IMU calibration to calibrate your compass as part of the procedure. These are completely separate operations, and if it's how you've set up your previous Phantoms, you've just been lucky that the compass happened to be ok when you did the IMU calibration.
     
  7. Jtrjr

    Joined:
    Mar 28, 2015
    Messages:
    444
    Likes Received:
    277
    Location:
    South Dakota
    Oso,

    No, I wasn't. My normal procedure for a brand new bird is to do an IMU cal straight from the box and then do the compass cal when I prepped for my first flight. I haven't had this issue before and I knew where the numbers were supposed to be. I didn't really think about the compass cal before the IMU cal. Just never did it that way before. I'm just trying to save others from wasting hours doing the IMU first. Thanks for the reply!

    Jerry
     
  8. Jtrjr

    Joined:
    Mar 28, 2015
    Messages:
    444
    Likes Received:
    277
    Location:
    South Dakota
    Rocky and others,

    I got it guys! Just trying to prevent others from making the same mistake as I stated in post #7. Thanks for the replies!

    Jerry
     
  9. Erroll

    Joined:
    May 15, 2015
    Messages:
    501
    Likes Received:
    212
    Location:
    South Africa
    This still doesn't make any sense. Quite simply calibrate the IMU, then calibrate the compass. No issue, no time wasted.
    The IMU calibration does not affect the compass Mod values.
     
    Oso likes this.
  10. Oso

    Oso

    Joined:
    May 19, 2015
    Messages:
    2,526
    Likes Received:
    1,477
    Location:
    Sacramento CA
    If the mod values other than compass were good as you noted, why did you then try another IMU cal and stay up until 3am? What were you trying to accomplish with the subsequent IMU calibrations? I'm sure I must not be understanding what you posted.
     
    Erroll likes this.
  11. Jtrjr

    Joined:
    Mar 28, 2015
    Messages:
    444
    Likes Received:
    277
    Location:
    South Dakota
    Obviously, my intent here was in vain. No biggie guys. Sorry I didn't catch it before I went through the process I described. I couldn't find an answer by searching. I hoped that if someone (in the future) made the same mistake and tried to do a search they'd find this post. That's all, that's it. I made a simple mistake and created an issue for myself, just trying to prevent others from doing the same. I'm not sure why that doesn't make sense but so be it. Thanks for the replies.

    Jerry
     
  12. Oso

    Oso

    Joined:
    May 19, 2015
    Messages:
    2,526
    Likes Received:
    1,477
    Location:
    Sacramento CA
    Now it does make more sense to me at least. There was no mention in your initial post that you knew you made a simple mistake, so your story was sounding like you somehow actually thought an IMU cal would fix your compass mod issues. That seemed contradictory to me based on your stated experience, so I wanted to know more in case there was a gap in my own understanding of the separate calibrations.

    I'm sure I speak for the others when I say that I do appreciate you trying to save any new pilots from making the same mistake you made. Cheers sir.
     
    Erroll and Jtrjr like this.
  13. Jtrjr

    Joined:
    Mar 28, 2015
    Messages:
    444
    Likes Received:
    277
    Location:
    South Dakota
    Oso,

    Thanks for the breathing room. The original post was at about 3am? I tried to be as clear as I could be at that time. I thought the post was rambling too much but felt a responsibility to get it out there. I searched everywhere I could about this issue and found nothing. I probably should have waited and gathered my thoughts. I'm not an expert at any of this stuff and never have claimed to be. I've learned a great deal from forums like this and try to share when I can. I'm usually pretty careful to proclaim that my findings are my "opinions" or "observations" only. From that standpoint, lesson learned. I do believe that my OP may possibly save someone the aggravation that I experienced by using the search tool on several forums. I sure hope it does!

    Thanks again for your responses!

    Jerry
     
    eaglegoaltender likes this.