Magnetometer coordinates differ testing on different devices

Hi all!

I am working with a 360 degree image, that one can navigate by moving an iPad around.

I use pictures from Ricoh Theta and bind them to a sphere. Then I get the magnetometer information using @trentbrooks' xCoreMotion (thanks for making the addon and putting this up!!) and make them into a ofQuaternion. At specific x,y,z I then add buttons to play specific sounds on touch.

I test on an iPad mini 4 gen and everything works ok, but I tried an iPad mini 2 and also an iPhone 5C and the magnetometer information is completely different, ranging to completely different numbers..

Am I doing something wrong? It seems unlikely that magnetometer coordinates are device specific or resolution dependent..
just looking at this:

ofVec3f m = coreMotion.getMagnetometerData();
cout<<"magnetometer x,y,z = "<< ofToString(m.x, 3) <<" "<< ofToString(m.y, 3) <<" "<< ofToString(m.z, 3)<<endl;

Many thanks for the help!