Step Response
Place the sensor on a rotatable test fixture. Let the heading reading settle. Manually rotate the fixture quickly (< 1 second) to a new position and record the heading as it (hopefully) settles to the new position. Then rotate the fixture back to the approximate starting position (to observe the response in both directions).
The general behaviour is approximately as expected - the heading adapts to the new orientation after the move. However, there is often a lot of over- or under-shoot in the response, and it takes many (> 4) seconds to close onto the new heading.
This behaviour is not always seen in the same magnitude and it is not yet known why. Compare the following two tests - the first graph shows a large oscillation as the heading converges; the second converges much more rapidly. However the second graph exhibits another undesirable characteristic - i.e. the heading does not always remain constant once motion has stopped.
This graph shows the output from all three available filters: Madgwick, Mahony, and NXP Fusion.
This graph shows the sensor reading for heading, plus pitch and roll. The latter two parameters are plotted against the second Y-axis, and they can be seen to be of small magnitude and to settle quickly. It is expected that the pitch and roll change with rotation, as the sensor is attached to the spokes of the wheel, which are not orthogonal to the axis of rotation of the wheel.