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Unable to get correct calibrated values from magnetometer

Question asked by Arthur van der Wal on Aug 4, 2014
Latest reply on Aug 11, 2014 by Arthur van der Wal



We are using the Freescal magnetometer sensor and accelerometer in order to determine 'an absolute' orientation.


We are calibrating the magneto data by subtracting an offset form the measurements. This offset is determined by finding extremes in all dimensions during during a calibration period, in which the user rotates the sensor around all axes.


After calibrating, we get a 360 rotation in the xy plane, however when the sensor is tilted, the readings start to make less sense. Also we see that the distribution of rotation is not lineair / uniform. It seems that the angular rotation in certain areas is much higher than others (I saw a related post on this forum, that remained unanswered:


mag3110 magnetometer calibration


If we plot the calibrated readings in a point cloud and rotate the sensor 360 degrees around all it's orthogonal axes, we don't see 3 'circles / ellipses' that are orthogonal to each other, this is quite troubling.


Our goal with the Freescale magnetometer sensor is to use it in combination with an accelerometer to determine an 'absolute' orientation, my question is, is this at all possible? Currently with the current data and readings we are unable to use the data of the magnetometer.


Thanks very much