China Neodymium And Ferrite Magnets Manufacturer & Supplier 
Although all “radial magnets” are magnetized along the diameter, the method for distinguishing polarity varies slightly depending on the magnetization type (standard radial, full radial radiation, radial multi-pole). These will be explained separately below.
First, there is standard radial magnetization, where magnetic field lines divide the magnet into two halves—the left side being N and the right side S, or vice versa. The polarity can be determined using a Gauss meter (which displays N or S pole) or the known-polarity magnet method.
The second type is fully radially radiated magnetization, where the magnetization direction at each point follows the radius, with no demarcated pole regions. Typically ring-shaped, the entire outer surface is the N pole and the inner surface is the S pole, or vice versa—such as outer N → inner S or outer S → inner N. Scanning the outer circumference with a Gauss meter will not reveal alternating N-S patterns. Similarly, magnetic visualization film will show the entire outer circle as a uniform color without alternating black-and-white stripes.
Relevant samples include: Radiation Sintered Ring Ferrite Magnet 25mm x 19.2 x 5 mm
The third type is radial multipole magnetization, with N/S alternation in the circumferential direction, commonly found in the rotor magnetic ring of brushless motors. The best way to distinguish polarity is also to use a Gaussian meter or a magnetic pole observation piece, where the magnetic pole observation viewing can quickly determine how many magnetic poles there are, as shown in the figure below with 16 poles.
The illustration shows a magnetized multipole neodymium ring with an inner circle (inner diameter), while the outer surface exhibits little magnetic properties.
The above outlines three common methods for distinguishing the polarity of radial magnets. Some magnets feature multi-pole skewed magnetization, which can be identified using similar techniques. If a magnet shows no visible changes on its surface, it may be unmagnetized—try attaching iron objects to test its magnetic properties.
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