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How cold is too cold for IMU cold cal?

Discussion in 'Pro/Adv Discussion' started by Wolfiesden, Feb 10, 2016.

  1. Wolfiesden

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    I am getting long IMU warmups due to the cold temps here. (15f). So how cold is too cold for doing an IMU cal? Is 10-15f too cold?

    And as spring rolls around, is it wise to re-cal the IMU as the temps rise?
     
  2. shockwave199

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    Never heard of too cold. Leave it out in those temps for 10-15 minutes and bring it in and do a calibration. I don't think you have to recalibrate for warm temps.
     
  3. Wolfiesden

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    Why not just leave it out and let it cal outside? Whats the reason to bring it inside and let it warm up while doing the cal?
     
  4. nix240z

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    you could leave it outside to do the IMU but you want a level surface while going a IMU calibration. I use a bubble level on a large piece of tile left over from a bathroom remodel
     
  5. Pete Leare

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    I only bring it in to use my pool table - perfectly flat! otherwise I would do it outside.
     
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  6. Wolfiesden

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    Appreciate that, I know it needs to be level. I have a shooting bench i can set up in the garage (to shield against wind). I can level that so a marble won't roll off it.
     
  7. shockwave199

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    It's not necessary to do the calibration in the cold too but if circumstances are right than fine.
     
  8. JickMagger

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    Is an occasional gust of wind enough to knock the calibration off? And does it matter if the copter is near metal when doing IMU calibration?
     
  9. Pete Leare

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    Yes, a (strong) wind gust would not be good. Even inside, you should not walk nearby when it's calibrating in fear of a floor vibration. Perfectly flat and perfectly still is the recipe. If you can't achieve that then move to where you can.



    Sent from my iPhone using Tapatalk
     
  10. JickMagger

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    So indoors it is, unless it's is a rare calm day. What about metal? Hard to find somewhere inside with no nearby metal.
     
  11. Pete Leare

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    It depends on your definition of nearby. If the cal fails but all the conditions were good then move it and try again. I have successfully calibrated within 6 feet of my home electrical panel if that helps?


    Sent from my iPhone using Tapatalk
     
  12. TheRealNick

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    Part of why I don't recommend doing an IMU calibration unless you have an issue....anyone know what temp DJI uses at the factory? Also you guys are leveling the skids....I would guess DJI uses a fixture that the arms sit on....if I even did one I would probably level the arms...
     
  13. tcope

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    Here is my take on the IMU temp... feel free to chime in if you think it's incorrect.

    The system components need to be at operating temps in order to be accurate (at least the barometer). So if you set it at 75F and go out into 35F temps, those components need to warm up to 75F before they can calibrate correctly. This means you need to wait. By calibrating at 45F you don't need to wait as long. However, calibration might be a little off if it's set when the temp is 35F and its already 75F.

    So here is _my_ recommendation... an indoor IMU calibration is just fine and only means you need to wait 30 seconds or so for warm up in colder weather. If you want to do a cold calibration, don't use really cold freezing temp... rather, something close to the current temps outside. If it warms up and is usually above those temps, recalibrate. So perhaps once in the winter and once in the spring.

    I think it's perhaps more safe to do a warm calibration and wait for the Phantom to warm up. But slightly cooler is not a big deal.
     
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  14. RedHotPoker

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    I have chilled my Phantom 3 Pro outside on the balcony, in the refrigerator and both methods seem to be adequate.
    A 15 minute chill down, directly before doing an IMU calibration seems about right. I allow my drone to do the initial start up, then press the IMU calibration button... My normal startup times have been reduced drastically. ;-)

    More time to fly, more reasons to smile.

    RedHotPoker
     
  15. neven

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    By "allow my drone to do the initial start up" you don't mean waiting for IMU warm up to finish before calibrating, right?
     
  16. shockwave199

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    A lot has been documented on this in a number of threads. There's no need for dramatics. Chill down the bird, bring it in, do an IMU immediately as soon as you can start it in the software, done. Warm up times in cold climates can be much more than 30 seconds. A cold IMU calibration really does solve the issue. I have had not a single problem since doing one back in the fall when the temps dropped and the warm up started delaying my flights for unknown amounts of time each flight, which was not acceptable for my purposes. That no longer happens. Worth it. If you have the luxury of waiting for warm up, so be it.
     
  17. RedHotPoker

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    @neven,
    Sorry I never replied back to you earlier, I must have missed the notification.
    No, I never allow it to warm up first. By initial start up, what I mean, is place it on a flat square surface & when you first plug in the battery to the chilled down drone, (the battery is removed for the cooling off period) turn it on, and once the esc's squeal, and the gimbal dance is done, hit the calibration button in the app. I get the RC ready and Go app on the correct page, ready to run it. As soon as the gimbal stops, then I tap the Calibrate IMU button. And don't touch the drone until it reaches 100%.
    After that, I do an actual gimbal calibration, then walk out side and complete a fresh Compass calibration. Done.

    RedHotPoker
     
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