China Neodymium And Ferrite Magnets Manufacturer & Supplier 
In the previous article, we introduced what a dual-track (code track) magnetic ring encoder is. Today's article will cover the technical requirements for dual-code-track magnetic disks/magnetic rings used in magnetic encoders.
1. Precision Arrangement of Magnetic Poles
Phase Difference Design
The dual-track magnetic ring consists of a primary track (Track 1) and a secondary track (Track 2). The magnetic pole periods of the two tracks exhibit a slight difference:
Primary track period λ
Secondary track period λ' = λ ± Δλ
The phase difference Δθ introduced by Δλ creates a “vernier effect,” enabling resolution subdivision. For example:
Main track period λ = 2 mm
Secondary track period λ' = 1.95 mm
This achieves a theoretical resolution of 0.05 mm per revolution.
In practical products, common design configurations include 32/31 pole pairs or 64/63 pole pairs, balancing precision with manufacturing feasibility.
Alignment Accuracy
The relative positional accuracy between dual tracks is critical. If the relative error exceeds ±5 μm, it will cause fine decoding errors, directly affecting the encoder's resolution and stability. Therefore, the manufacturing of dual-track magnetic rings requires extremely high precision in magnetic pole printing and magnetization process control.
Dual-track magnetic rings with different poles are used for encoders.
2. Magnetic Signal Quality and Consistency
High-quality magnetic signals are essential for reliable encoder operation. The magnetic properties of dual-track magnetic rings must meet the following requirements:
1. Surface magnetic flux density must reach at least 20 mT to ensure stable recognition by the magnetic sensing chip.
2. The difference in magnetization intensity between dual tracks must be less than 5% to prevent decoding errors caused by inconsistent signal amplitudes.
3. Single-pole deviation should be controlled within 1.5% to ensure uniform spacing and amplitude between magnetic poles, thereby guaranteeing stable output waveforms.
3. Mechanical Structure Requirements
Beyond magnetic signals, the mechanical properties of magnetic rings are equally critical. Since encoders are typically mounted on motor shafts or rotating components, their geometric precision directly impacts signal quality. Key requirements include, Radial runout tolerance ≤ 0.05 mm. Axial end-face parallelism ≤ 0.03 mm. Mounting coaxiality ≤ 0.1 mm (relative to shaft centerline)
This concludes the article. For inquiries regarding encoder multi-pole ring magnet samples or pricing, please send us an inquiry.
Some samples;
128 poles and 126-poles multipole magnetic encoder ring magnets