Absolute Magnetic Rotary Encoder — OMR Series
The OMR series is a high‑precision absolute magnetic rotary encoder system, designed for industrial motion control, robotic joints, and servo feedback applications. It serves as a core feedback element for position and velocity control loops.
- Ultra-high resolution down to 0.1 arcsecond (~0.000028°)
- Multi-protocol output: BiSS-C, SSI, MODBUS-RTU, Tamagawa
- IP67 rated, operating range –20°C to +80°C
- Compact 53 × 14 × 12.5 mm aluminum housing
What Is the OMR Absolute Magnetic Rotary Encoder?
The encoder system operates on a non‑contact absolute measurement principle, incorporating a highly reliable safety chip and a precision dual‑track magnetic ring to ensure long‑term stability in harsh industrial environments.
1. Anatomy of the OMR Encoder System
The OMR combines three core elements to deliver absolute angular position feedback:
Magnetic Ring (Target)
A precision dual‑track magnetic disc with a master track (2 mm pole pitch, N/S alternating) and a nonius track for the absolute reference. The ring is the rotating element mounted to the shaft.
Hall-Effect Sensor Array
A high‑performance Hall‑effect sensor array reads both the master and vernier tracks simultaneously, detecting the alternating magnetic field generated by the precision magnetic ring.
ASIC Signal Processing & Output
The raw signals are processed in a dedicated ASIC through signal conditioning and proprietary algorithms to determine absolute position, then output via BiSS-C, SSI, MODBUS-RTU, or Tamagawa.
2. Measurement Principle
The OMR uses a dual‑track magnetic disc (ring) as its measurement reference. The magnetic layer is magnetized through an elastomer layer with two tracks: the master track is magnetized with a 2 mm pole pitch (N/S alternating), while the nonius track provides the absolute reference. This rotary magnetic scale (nonius) architecture is what enables true absolute, single-turn measurement without a homing sequence.
The encoder integrates a high‑performance Hall‑effect sensor array to read both the master and vernier tracks. The alternating magnetic field generated by the precision magnetic ring is processed in the dedicated ASIC through signal conditioning and proprietary algorithms to determine the absolute position.
Why Industrial Motion Control Needs the OMR Series
Four scenarios where the OMR absolute magnetic rotary encoder is the right feedback solution.
1. Absolute Position on Startup
True absolute measurement means no homing sequence on every power-up. Absolute position is available within 300 ms at power-up — critical for fast startups and safe emergency stops.
2. Harsh Environment Immunity
IP67 protection against dust and moisture, plus 0.5 mT immunity to external magnetic fields — reliable even near motors and other strong stray-field sources.
3. High-Speed Real-Time Feedback
Position updates complete in less than 5 µs, supporting high-speed real-time control loops for servo and motion applications.
4. Flexible Multi-Protocol Integration
Native support for BiSS-C, SSI, MODBUS-RTU, and Tamagawa over RS422/RS485 — drop-in compatibility across a wide range of industrial controllers.
Key Features of the OMR Series
Engineered for precision, durability, and seamless industrial integration.
True Absolute Measurement
Dual‑track nonius encoding delivers a unique absolute position within one revolution — no battery, no homing, no incremental accumulation errors.
Contamination-Proof
IP67 rated against dust and moisture ingress. Unlike optical encoders, the magnetic principle has no optical path to obstruct.
Non-Contact & Wear-Free
Non-contact magnetic sensing means zero mechanical wear and a long operational lifespan — ideal for sealed, maintenance-free assemblies.
Ultra-High Resolution
Resolution down to 0.1 arcsecond (~0.000028°) with absolute accuracy ≤0.05° and repeat accuracy of 0.005°.
Flexible Output Interfaces
Full support for BiSS-C (10 MHz), SSI (1 MHz), MODBUS-RTU (256 Kbps), and Tamagawa (2.5 Mbps) over differential RS422 and serial RS485.
Integrated Diagnostics
A built-in LED provides real-time visual status — normal operation, over-temperature warning, and error states for rapid field troubleshooting.
OMR Encoder Series
OMR Series Specifications
Mechanical, electrical, and performance specifications for the OMR absolute magnetic rotary encoder.
Mechanical
The encoder housing is made of aluminum, with dimensions of 53 × 14 × 12.5 mm and a mounting hole spacing of 46 mm. Its compact form factor enables easy integration into space‑constrained applications.
Electrical
Operates from a 5 V ±5% supply, drawing less than 160 mA (no‑load, 25°C). Output types: differential RS422 and serial RS485, with ±40 mA load capability. Cable length: 0.5 m to 10 m.
Environmental
Rated IP67, operating range –20°C to +80°C. External magnetic field immunity: 0.5 mT, ensuring reliable operation near motors and stray-field sources.
Communication Interfaces
The OMR supports a wide range of industrial communication protocols for flexible integration:
| Protocol | Interface | Maximum Rate |
|---|---|---|
| BiSS-C | RS422 | 10 MHz clock |
| SSI | RS422 | 1 MHz clock |
| MODBUS-RTU | RS485 | 256 Kbps |
| Tamagawa | RS485 | 2,500,000 bps |
Performance Specifications
The OMR delivers outstanding angular measurement performance:
| Parameter | Specification |
|---|---|
| Resolution | 0.1 arcsecond (~0.000028°) |
| Repeat accuracy | 0.005° (at 0.3 mm air gap) |
| Absolute accuracy | ≤0.05° |
| Maximum measuring length | 16.4 m |
| Maximum speed – magnetic ring | up to 10,000 rpm (HDA82 high‑speed version) |
| Maximum speed – linear scale | up to 8 m/s |
| Sensing gap | ≤0.6 mm, optimal at 0.3 ± 0.1 mm |
Status Indication and Diagnostics
A built‑in LED on the top of the encoder provides clear visual status feedback:
| LED State | Meaning |
|---|---|
| Solid blue | Normal operation – position data valid |
| Flashing blue | Warning – internal temperature exceeds 80°C |
| Solid purple | Error – position data invalid (possible causes: demagnetized ring, or the encoder left and re‑entered the magnetic field during operation) |
| Solid red | Error – position data invalid (possible causes: excessive air gap, no magnetic ring detected, or internal fault) |
| Irregular alternating red/purple | Error – encoder is misaligned with the magnetic ring |
| LED off | No power supply connected |
Compatible Magnetic Rings
The OMR series supports the following standard magnetic ring models (ID, OD, and height H are configurable). For non-standard sizes, see our custom magnetic encoder ring capabilities and the full precision magnetic rings and encoder disks range:
| Model | Outer Diameter (mm) | Inner Diameter (mm) | Height (mm) |
|---|---|---|---|
| ME-MRR-082 | 81.53 | 60 | 14 |
| ME-MRR-122 | 122.29 | 100 | 14 |
| ME-MRR-163 | 162.97 | 140 | 14 |
| ME-MRR-204 | 203.82 | 174 | 12 |
| ME-MRR-223 | 229.18 | 190 | 12 |
| ME-MRR-326 | 325.94 | 285 | 12 |
Common Questions About the OMR Series
What is an absolute magnetic rotary encoder?
It is a position sensor that reads the magnetic field of a rotating dual-track ring using a Hall-effect array to determine a unique absolute angle — no homing, battery, or optical components required.
Which communication protocols does the OMR support?
The OMR outputs BiSS-C and SSI over RS422, plus MODBUS-RTU and Tamagawa over RS485, for seamless integration with a wide range of industrial controllers.
How do I select the correct magnetic ring for the OMR?
Choose from six standard ring models (81.5 mm to 326 mm OD). ID, OD, and height are configurable — for non-standard sizes, we offer full custom magnetic encoder rings.
What sensing gap should I maintain?
The sensing gap should be ≤0.6 mm, with an optimal value of 0.3 ± 0.1 mm, to ensure reliable signal quality and accuracy.
What is the OMR operating temperature range?
The OMR operates from –20°C to +80°C and is rated IP67 for dust and moisture ingress. It also tolerates external magnetic fields up to 0.5 mT.
Can the OMR be customized?
Yes — cable length (0.5 m to 10 m), output protocol, and magnetic ring dimensions can all be configured to your requirements. Contact our engineering team for a tailored solution.
Ready to Spec Your OMR Encoder?
With its high precision, non‑contact measurement, flexible communication interfaces, and compact mechanical design, the OMR series absolute magnetic rotary encoder is an ideal position feedback solution for industrial automation, robotics, and servo control applications. Tell us your protocol, mechanical constraints, and accuracy goals — we’ll recommend the optimal configuration.
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