PRODUCT OVERVIEW
Absolute Magnetic Linear Encoder — OTV-AL200 Series
True Dual-Track Absolute Encoding · IP67 · BiSS-C / SSI / RS-485 · 0.1 μm Resolution
1. What Is an Absolute Magnetic Linear Encoder?
In linear motion control, magnetic encoders have overtaken optical systems as the preferred choice in harsh industrial environments. The reason is straightforward: non-contact, wear-free operation with no glass disc to break and no optical path to keep clean.
The OTV-AL200 Series is a true dual-track absolute magnetic linear encoder system — a complete solution that includes a readhead paired with a high-quality linear magnetic encoder strip. Unlike incremental systems that lose position at power-off, the AL200 delivers a valid, unique absolute position within 350 ms of power-up. No homing routine. No battery backup. No incremental counter to lose.
2. How It Works: Dual-Track Magnetic Encoding
The AL200 readhead integrates a sensor IC (compatible with iC-MU and iC-MU200 series) that reads two parallel magnetic tracks on the encoder strip simultaneously:
Incremental Track (Master)
A precise alternating N-S pole pattern with a standard 2 mm pole pitch. This track provides high-resolution relative position data through the sensor’s onboard interpolator.
Absolute Track (Nonius)
A uniquely coded binary pattern that repeats only once over the entire 16,384 mm measurement range. The readhead compares the phase difference between the two tracks — using the Nonius (Vernier) principle — to compute a unique absolute position within one code cycle.
Because sensing is non-contact, there is zero mechanical wear. Signal processing latency is extremely low (< 62.5 μs), making the AL200 suitable for high-bandwidth servo control loops.
Key advantage over incremental encoders: No reference mark search on startup. If a machine axis loses power mid-operation, it recovers its exact position immediately — critical for safe restart in automated production lines, semiconductor handling, and multi-axis gantry systems.
3. Performance Specifications
The OTV-AL200 is engineered for stability and broad controller compatibility. Below are the parameters that matter for system integration.
| Parameter | Specification | Notes |
|---|---|---|
| Absolute Resolution | Up to 0.1 μm | Sub-micron precision control |
| Max Travel Speed | 5 m/s | Suitable for high-speed linear motors |
| Unique Code Length | 16,384 mm | Unique absolute position over 16.38 m |
| System Accuracy | ±20 μm/m | Tape accuracy; can be improved with calibration |
| Communication Protocols | BiSS-C, SSI, RS-485, Panasonic, Tamagawa | Broad drive and controller compatibility |
| Supply Voltage | 4.75 – 5.5 VDC | Reverse polarity protected |
| Protection Class | IP67 (epoxy potted) | Waterproof, oil-proof, dust-resistant |
| Position Update Latency | < 62.5 μs | Suitable for high-bandwidth servo loops |
| Startup Time | ~350 ms | Absolute position available; no homing |
Environmental & Mechanical
| Parameter | Specification |
|---|---|
| Readhead Operating Temp | –10 °C to +55 °C |
| Readhead Storage Temp | –20 °C to +85 °C |
| Magnetic Tape Temp Range | –20 °C to +70 °C |
| Vibration Resistance | 300 m/s² (~30 G), 55–2000 Hz (IEC 60068-2-6) |
| Shock Resistance | 300 m/s² (~30 G), 11 ms |
| EMC Immunity | EN IEC 61000-6-2:2019 |
| EMC Emission | EN IEC 61000-6-4:2019 |
| Max External Magnetic Field | < 1 mT (operating); > 25 mT causes irreversible tape damage |
| Housing Material | Stainless steel — rugged, excellent EMC compatibility |
4. Installation Guide
The relative position between the readhead and the linear magnetic encoder strip is critical to achieving rated performance. Magnetic encoder accuracy depends directly on maintaining the correct air gap and alignment tolerances.
4.1 Key Installation Tolerances
| Parameter | Tolerance |
|---|---|
| Recommended Air Gap | 0.3 ± 0.1 mm |
| Lateral Offset | Readhead centered over tape; excessive offset reduces field strength and degrades accuracy |
4.2 LED-Assisted Alignment
The OTV-AL200 features a built-in status LED for real-time alignment verification:
| LED State | Meaning | Action |
|---|---|---|
| Solid Green | Signal optimal — installation correct | None |
| Red Flashing | Marginal signal — gap near limit | Re-check air gap and alignment |
| Solid Red | No signal — gap too large, tape demagnetized, or readhead misaligned | Verify tape presence and gap; inspect for external magnetic field exposure |
Installation tip: Use a 0.3 mm plastic feeler gauge between the readhead and tape during mounting. After securing the readhead, move it along the full travel length and verify the LED remains solid green at every position before commissioning the axis.
5. Applications
- Semiconductor Equipment: Wafer handling stages, inspection systems, lithography positioning
- Lithium Battery Manufacturing: Electrode winding, slitting, stacking, calendaring
- Linear Motors & Direct Drive: Iron-core and ironless linear stages, voice coil actuators
- CNC & Precision Machining: Linear axes on grinding machines, milling centers, EDM
- Medical & Laboratory Automation: Precision positioning stages, scanning systems, liquid handling
- 3C & Electronics Assembly: Pick-and-place, dispensing, automated inspection
6. Why Choose the OTV-AL200?
- True absolute on startup: 350 ms to valid position. No homing. No battery. No lost reference marks.
- Contamination-proof: IP67 epoxy-potted readhead. Magnetic sensing — no optical path to obstruct.
- Broad protocol support: BiSS-C, SSI, RS-485, Panasonic, Tamagawa — compatible with mainstream drives and controllers.
- Sub-micron resolution: 0.1 μm absolute resolution supports the most demanding positioning applications.
- Long measurement range: 16.38 m unique absolute code length; tapes can be joined for longer axes.
- Stainless steel housing: Rugged mechanical design with excellent EMC compatibility for industrial environments.
7. Frequently Asked Questions
Q: What is the difference between absolute and incremental magnetic linear encoders?
A: An absolute encoder outputs a unique position value immediately after power-up �� no homing or reference mark search required. An incremental encoder counts pulses from a known reference and loses position when power is removed. The OTV-AL200 is a true absolute system: valid position data is available within 350 ms of power-on.
Q: What air gap is required between the readhead and magnetic tape?
A: The recommended air gap is 0.3 �� 0.1 mm. Use the supplied 0.3 mm plastic feeler gauge during installation. The readhead LED provides real-time gap feedback �� solid green indicates correct alignment across the full travel range.
Q: Which communication protocols are supported?
A: BiSS-C, SSI, RS-485, Panasonic, and Tamagawa protocols are all supported. Select your protocol at time of order �� the readhead hardware is common across all options.
Q: Can the magnetic tape be cut to length on site?
A: Yes. The MSA series magnetic tape is supplied cut to your specified length. For lengths exceeding the 16,384 mm unique code cycle, multiple tape segments can be joined. Contact OTV for joining instructions and longer-axis reference designs.
Q: What is the maximum measurement length?
A: A single tape segment provides a unique absolute code over 16,384 mm (16.38 m). For longer axes, multiple tapes can be joined. The readhead seamlessly transitions between segments.
Q: Can the OTV-AL200 operate in harsh environments?
A: Yes. The readhead is IP67-rated and epoxy-potted for protection against water, oil, and dust. The magnetic sensing principle has no optical components to foul. The stainless steel housing provides excellent EMC shielding. Operating temperature range is -10 ��C to +55 ��C (readhead) and -20 ��C to +70 ��C (magnetic tape).
Q: Is the OTV-AL200 compatible with standard servo drives?
A: Yes. With BiSS-C, SSI, and RS-485 protocol support, the AL200 interfaces directly with mainstream industrial servo drives and motion controllers from vendors including Elmo, Copley, Beckhoff, Siemens, and Mitsubishi.
Need an Absolute Linear Encoder for Your Application?
OTV Sensing provides complete absolute magnetic linear encoder systems — readhead + magnetic tape — with full technical support from installation to commissioning. Tell us your stroke length, accuracy requirements, and controller protocol.
Request a Quote or Technical Consultation →OTV Precision Sensing — Absolute Magnetic Linear Encoder Series. Specifications subject to change without notice. Document: OTV-AL200-TS-EN-2026.