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IMU CCALIBRATION TEMPERATURE QUESTION!.. PLS HELP !
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Airspace Explor
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AG0N-Gary Posted at 2016-6-4 17:50
You may be thinking that you are calibrating it to a specific temperature.  You're calibrating it t ...

Does the P3 series have an IMU heater? What is your source for this?
2016-6-5
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dobmatt Posted at 2016-6-5 01:58
I'm not sure about this ... We don't really know if DJI-Ken or DJI-Paladin are a "tech" persons, a ...

Hey! 2 - 3 minutes is 10% less flight time.
2016-6-5
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dobmatt
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Airspace Explor Posted at 2016-6-5 22:20
Hey! 2 - 3 minutes is 10% less flight time.


Absurd, my friend. The drone is warming up on the ground with no idling motors, energy usage is negligible and has no noticeable effect on flying time. You're confusing battery warming up, which indeed may steal some flying time with drone hovering above ground.
2016-6-5
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Rnfaust Posted at 2016-6-4 17:30
The pads seem even enough for this guy.
I level the base first - not that it really matters.
I thi ...

For my most recent IMU calibration, I leveled a base plate when the drone was sitting on it then tested the level of a plate resting on the motor spindles. A bubble level indicates the same - base or top.

I find it easier to read the bubble level when it's placed on the top plate and easier to shim the foot pads than shim a base plate.
2016-6-6
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dobmatt Posted at 2016-6-5 13:25
Absurd, my friend. The drone is warming up on the ground with no idling motors, energy usage is ne ...

Agreed. I meant to say that's time waiting for the UAV to be ready for flight instead of actually flying. For those with a production schedule, or merely impatient, it would be important.
2016-6-6
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Rnfaust
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Airspace Explor Posted at 2016-6-5 22:18
Does the P3 series have an IMU heater? What is your source for this?

Don't you figure it's just a figure of speech?
I can't imagine a need to heat things up beyond what the battery and current do naturally. IMO
2016-6-7
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Not A Speck Of
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Rnfaust Posted at 2016-6-8 04:38
Don't you figure it's just a figure of speech?
I can't imagine a need to heat things up beyond wh ...

My understanding is that the IMU is indeed heated. Whether it uses a "heater" or utilizes heat from current I'm not sure, but the following video uses the term "heater". Start it at the 2:45 point.



2016-6-7
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Rnfaust Posted at 2016-6-7 13:38
Don't you figure it's just a figure of speech?
I can't imagine a need to heat things up beyond wh ...

Some instruments have a temperature controlled oven for the temperature dependent sensors. Some aircraft (not necessarily hobby grade aircraft) undoubtedly do run their sensors at constant temperature. Hobby grade aircraft may use a simpler temperature compensating arrangement for lower cost, lower weight, lower battery draw or they simply tolerate the inevitable inaccuracies over the operational temperature band.

An oven system would not need to be cooled to ambient for calibration. This leads me to believe the sensor system used in Phantom 3 uses a temperature compensating design. If someone were to open the shell and inspect the electronics, they could likely determine which is used.
2016-6-7
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Rnfaust
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Airspace Explor Posted at 2016-6-7 13:48
For my most recent IMU calibration, I leveled a base plate when the drone was sitting on it then t ...

Anecdotally speaking, after a crash a year ago and then me straightening the frame (shell) with a heatgun, one arm is just a bit lower than the other three. Before that, a blade was actually hitting the shell. The landing gear was straight and flat though because it landed upside down. BTW: It still flies and hovers great. So, it might not be the end of the world if it's off slightly. I'm sure however, the IMU would object to even slight vibrations or other movement during calibration.
2016-6-7
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Rnfaust Posted at 2016-6-7 13:54
Anecdotally speaking, after a crash a year ago and then me straightening the frame (shell) with a  ...

In any case, I admire your ingenuity for designing a test fixture from materials at hand.
2016-6-7
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Rnfaust
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Not A Speck Of  Posted at 2016-6-8 04:51
My understanding is that the IMU is indeed heated. Whether it uses a "heater" or utilizes heat fro ...

Thanks for the Video link. But I still think it's a figure of speech. I'll bet things quickly heat up inside the shell.
Too bad all this is basicly folklore, since DJI hasn't offered official guidance (that I've been able to find).
True that the cooler the P3 and battery are during calibration, the faster it subsequently warms up. Beyond that, who knows for sure?
Just wondering though - if the P3 feels it must warm up to a predetermined point to consider the readings usable, why would we want to set that point to an unnaturally low point? Might that cause it to operate in some unintended way? Where are the DJI Engineers when we need them?
2016-6-7
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Rnfaust
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Airspace Explor Posted at 2016-6-8 04:52
Some instruments have a temperature controlled oven for the temperature dependent sensors. Some ai ...

There you go - I'll bet it compensates based on the temp. DJI knows how to work the numbers (obviously).
Thanks. That's my new working theory - until we hear from the team that built it.
2016-6-7
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Rnfaust Posted at 2016-6-7 14:35
Thanks for the Video link. But I still think it's a figure of speech. I'll bet things quickly heat ...

RE: "Where are the DJI Engineers when we need them?"

That question makes calibration temperature seem like a straight-forward one.
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Rnfaust Posted at 2016-6-7 14:35
Thanks for the Video link. But I still think it's a figure of speech. I'll bet things quickly heat ...

RE: "... why would we want to set that point to an unnaturally low point?"

And that's why I calibrate near to the temperature in which I will be operating.

Look, it could be that whomever came up with this "calibrate when cold" theory lived in a climate in which the outside (where flying is done) is cooler than the temperature in a climate controlled building. So, of course, it makes sense to cool the aircraft as far as practical before calibration indoors where it is comfortable. Was that person thinking globally, and seasonably, at the time?
2016-6-7
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Rnfaust
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Airspace Explor Posted at 2016-6-8 06:22
RE: "Where are the DJI Engineers when we need them?"

That question makes calibration temperature  ...

Please go on...
2016-6-7
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Rnfaust Posted at 2016-6-8 07:35
Thanks for the Video link. But I still think it's a figure of speech. I'll bet things quickly heat ...

The issue goes way back to the P2 series and DJI have never explained why.
http://www.phantompilots.com/thr ... -calibration.22688/

I just know that the MC temp warning on the P2 was there for a reason and many argue that it was just a bug. I also know going from hot to cold will cause the bird to take longer for the IMU to warm up.

Best practice for an IMU is to not fly it for an hour and do it in the mornings in cool place. Its also best practice to do it the moment you fire up the P3. The longer you let it idle, the warmer it will be in the shell, the longer the IMU calibration will take (and possibly fail).

On a side note, keeping the X and Y axis level will help the stationary YAW. If its not levelled with the horizon in both X and Y axis, you will find that the bird will have a wider yaw circumference. If the P2/P3 spins in one spot, then the calibration is perfect.

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This DJI tutorial on IMU calibration precautions against overheating during calibration and to calibrate indoors at room temperature from 20°C to 25°C. There's no mention of 'cold'. You can prevent overheating during calibration by starting calibration right after aircraft power-up.

2016-6-12
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