SBAU419 November 2022 TMAG5170
The multi-pole radial ring magnet is a custom magnet type made possible with a ring shape. In this magnet type, the magnet will be divided into alternating sections with radial polarization. Pole count for this magnet type is set by selecting the number of visible poles (North and South) when traversing the outer circumference. The number of poles should always be even.
Due to the radial polarization, the inner circumference shows a pattern of alternating poles, which is opposite that of the outer circumference. This accurately reflects the direction of the field vectors along each circumference, although the inner circumference poles are not included in the total pole count.
A multi-pole ring magnet is useful when implementing rotary encoding using a 2D latch. The magnet pictured in #GUID-CD8DB9F8-7346-406D-8745-96ACD6940A9B produces eight polarity transitions per revolution. This can be divided into four North-South pole pairs. As each pair passes, four unique output states are produced by the 2D latch, with each state change representing a 22.5° change in rotation. Alternately, a 3D linear device can be used to calculate relative angle at a 4:1 turn ratio with the same magnet. Sensors are typically placed radially outward from the magnet center.