If you know the Hz, that is full cycles per second, 2pi radians/sec per Hz. At steady 80Hz you get steady 160pi rad/s.
If you could put a pot on the end of the bar, could you put a short bar magnet aligned across the spin axis center?
A linear Hall sensor positioned over the center of that, when the sense axis is aligned with the magnet axis will read max (might need tuning) while off-alignment reads give cosine of angle factored values.