Magnetometer interference?

[Jim Bauer]

I am hoping you can shed a little light on a problem I am having with the BerryIMU v2. I am building an instrument to provide location and orientation information for a small aircraft, I am using the BerryIMU v2 with a Raspberry PI 3 to provide the attitude data. I have mounted the IMU directly to the RPi’s 40-pin GPIO header using the supplied 6 pin header. I have been successful with roll and pitch but, I am struggling with heading; when I rotate the unit, the heading values do not vary as expected so, I am wondering if there is a possible magnetic interference issue between the magnetometers and the metallic bits of the Raspberry Pi… is this something you have seen in the past? Of course, the other possibility is that I have messed up my coordinate orientation because of how I have mounted the IMU within the system… skull logo facing forward and rotated 90deg clockwise to direction of forward level motion.

[Mark Williams]

Hi Jim,  you would need to calibrate the compass to get a good heading. Here is some information about the types of interference an that can effect a magnetometer https://ozzmaker.com/compass3/

The biggest one is hard iron distortion.

If you are using python, you can use this script to get your calibratation values.
https://github.com/ozzmaker/BerryIMU/blob/master/python-BerryIMU-gryo-accel-compass/calibrateBerryIMU.py

 

 

Mark --OzzMaker.com --

[Jim Bauer]

Thank you Mark, I have gone through your _EXCELLENT_ tutorials on calibration and, seem to be making some progress… I am struggling a little now with understanding the coordinate transformation for heading (esp. including tilt compensation) … I will go through your tutorials in some more detail but, I may end up with more questions 🙂

Thanks again for your help!

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