Magnet offset, also known as run out or eccentricity, is when the magnet axis is not concentric with the axis of rotation. So 1 mm of eccentricity corresponds to the magnet center being offset 1 mm from the rotation axis. Figure 2-19 shows conceptually what eccentricity looks like for rotating a magnet 360°. Figure 2-20 and Figure 2-21 show the impact of eccentricity.

Worst case magnet offset considered here is 2 mm, which is 15% the size of the magnet diameter. In this case, the absolute error and standard deviation of difference both increase linearly with the magnet offset for the side by side die, while the stacked die centered on the axis of rotation has comparatively negligible error or variation.