How to calculate the pole pitch of a multipole magnetic ring?

Multipole magnetic rings are primarily used in magnetic encoders, motors, and sensors, where their core function is to provide regularly distributed magnetic pole signals for measuring angle, speed, or displacement. During design and application, the spacing between magnetic poles (magnetic pitch) is a critical parameter that directly impacts sensor resolution and signal quality.

Regarding magnetic pitch, for those less familiar with the term, it refers to the circumferential distance between adjacent poles (N pole to S pole) on a magnetic ring, also known as the magnetic gap. Proper magnetic pitch ensures the magnetic sensor accurately detects each pole change, enabling precise angle or position measurement.

How to calculate the pole pitch of a multi-pole magnetic ring?

To calculate the pole pitch of a multi-pole magnetic ring, you need to know the ring's outer diameter, inner diameter, and total number of poles (one pair of poles equals two poles). For example, an 8-pair magnetic ring has a total of 16 poles.

63-pole 64-pole dual-channel magnetic ring

For example, a multi-pole ring magnet with an outer diameter of 65mm, inner diameter of 58mm, and 128 poles uses the formula: 2πR (circumference) / number of poles

Radius = (Outer diameter + Inner diameter) / 4 = (65 + 58) / 4 = 30.75mm, or (65/2 + 58/2) / 2, yielding the same result.

Then divide the circumference by the number of poles: 2 × 3.1416 × 30.75 / 128 ≈ 1.51 mm.

Alternatively, use π × D ≈ 3.1416 × 61.5 mm ≈ 193.2 mm. How did we get 61.5 mm? It's 65 mm + 58 mm / 2 = 61.5 mm.

Then divide 193.2 by 128, which is approximately 1.51 mm.

The above outlines the calculation formula for the magnetic spacing of multi-pole magnetic rings. A physical spacing of 1.51 mm indicates extremely dense magnetic poles. When installing sensors, the air gap (distance between the sensor and the magnetic ring surface) must be extremely small and stable. Otherwise, the magnetic field signal will become blurred, leading to measurement errors.

Direct link to the Multipolar Magnetic Ring Products section on the website: https://www.couragemagnet.com/motor-multipole-magnets/

Are you curious?

Is the number of magnetizing poles of a magnet unlimited?