Why does an IMU need to warm up?

[Mako79]

I'm surprised nobody answered.... Because it was cold.....

This actually true. It needs to warm up because its cold.

Usually IMU's don't need to be warmed up (third party gimbals, track cars, etc...) An IMU just has a gyro and accelerometer.
IMUs on quads are different. They have a barometer built in. The barometer works by pressure and heat affects pressure.
If you are finding it long for the IMU to warm up, then you need to recalibrate your IMU via the PC/MAC assistance software.
This is to do with climate - DJI claims they have climate controlled room where the calibration happens. The only problem is that its not your country's climate.
If its 25 degrees in the DJI climate controlled room and you take it to a place that 10 degrees then the Mavic/Quad may take 5 minutes to warm up. This can be bad if you are trying to quick launch. What's the point of having a Mavic if it takes you 10 minutes to launch??

Just remember, when you do your IMU calibration, don't fly your mavic for an hour or so and keep it in a cool room (do not refrigerate - condensation). Try doing the calibration immediately the moment you turn on the mavic (the cooler the Mavic is, the better). If the Mavic is too hot, the calibration may be inaccurate and could fail. Remove props and gimbal locks and read the screen instructions as it will instruct you to rotate the mavic in 5 different axisissisis. And do it on a flat levelled surface as this minimises yaw drift.

Many will say not to do the IMU calibration, but I think it should be done as DJI does not know the Mavic owners will be flying.

 

[ChayD]

A bit late to the conversation here, and sort of unrelated (well it does relate to a DJI product so...). I noticed the circuit board for the IMUs on some faulty DJI OSMO 2 and 3 gimbals were getting quite toasty (based on touching the board with a finger) and assumed that the IMU had an internal short and had died, however in retrospect it looks like they have surrounded the IMU with some resistors that are deliberately designed to preheat it and it was those that were getting hot and not the IMU itself. The board around the IMU had been milled out in order to prevent the heat from escaping and enable better thermal control. Quite a neat bit of design.