Multi-track Gray code · pseudo-random
Absolute Encoder Disc
An absolute encoder disc gives every angular position a unique code, so the encoder knows the shaft position the moment it powers up — no homing run. The two common layouts are multi-track Gray code (n tracks for n bits) and a single pseudo-random track read by a detector array, combined with an incremental track for interpolation.
Also searched as: absolute encoder disk · absolute code disc · Gray code disc · pseudo-random encoder disc · absolute code wheel
- Multi-track Gray code or pseudo-random + incremental track
- Photolithographic patterns with precise track-to-track alignment
- Chrome-on-glass or reflective metal substrates
- Track radii and code layout to your drawing
- 100% AOI on every disc
Specifications
| Parameter | Absolute Encoder Disc |
|---|---|
| Substrates | Optical glass (chrome on glass) · stainless steel (reflective) |
| Optical path | Transmissive or reflective |
| Code | Multi-track Gray code · single-track pseudo-random + incremental track |
| Resolution | Expressed in bits (2ⁿ positions per revolution); to your drawing |
| Pattern process | Photolithography + etching |
| Contour machining | Laser OD cutting · laser bore machining |
| Inspection | 100% AOI machine vision; vision measuring machine; optical density / reflectance testing |
| Capacity | About 30,000 discs per day (all product lines combined) |
What we can customize
- Bit count, code type and number of tracks
- Reading radius of each track
- Incremental track for interpolation
- Outer diameter, bore and thickness
- Centering reference ring and alignment marks
Ordering information
| Quotation | Engineer reviews your drawing for manufacturability, then quotes with sample and production lead times |
|---|---|
| Minimum order quantity (MOQ) | 100 pcs |
| Standard lead time | 5–7 days (confirmed in the quotation) |
| Certifications | ISO 9001 (since 2012) · ISO 14001 |
| Manufacturer | ENC7 — Langfang Jingzheng Optoelectronic Technology Co., Ltd., factory-direct since 2007 |
Typical applications
Why pattern accuracy matters more on absolute discs
An absolute pattern is more complex than an incremental one: several tracks must be aligned to each other and concentric with the bore, and every code transition must land where the decoder expects it. That demands high lithographic accuracy and careful centring — at a 20 mm reading radius, 5 µm of eccentricity already causes about 52″ of angular error (eccentricity error explained). Every ENC7 disc is checked by 100% AOI and a vision measuring machine.
Send your drawing to sales@enc7.com or request a quote.
Glass vs. reflective metal vs. PC encoder discs
| Criterion | Glass (chrome on glass) | Reflective metal | PC (polycarbonate) |
|---|---|---|---|
| Typical optical path | Transmissive | Reflective (source and detector on the same side) | Transmissive |
| High line counts / absolute multi-track | Easiest | Possible, limited by etching and coating | Moderate resolution |
| Thermal expansion (approx.) | Low — about 3.3 (borosilicate) to 9 (soda-lime) ×10⁻⁶/K | Higher — stainless steel about 16–17 ×10⁻⁶/K | Highest — about 65–70 ×10⁻⁶/K |
| Shock and vibration | Sensitive to drops and impact | Very good — does not shatter | Good — tough, not brittle |
| Encoder height | Needs space on both sides | Can be very thin | Needs space on both sides |
| Relative cost | Higher | Lower than glass | Lowest |
| Best for | CNC, rotary tables, metrology, high-resolution servo | Robot joints, slim servo motors, hollow-shaft encoders | High-volume, cost- and weight-sensitive encoders |
Full comparison: Reflective metal or glass encoder disc? How to choose
Quality control on every disc
- 100% AOI — automated optical inspection of graduation integrity, pitch and surface defects (scratches, spots, chips).
- Vision measuring machine — critical dimensions such as outer diameter, bore and pattern-to-bore concentricity are verified.
- Optical density testing — transparent and opaque areas are measured on transmissive discs.
- ISO 9001 quality management system, certified since 2012; ISO 14001 environmental management system.
- MOQ 100 pcs, standard lead time 5–7 days.
Frequently asked questions
When do I need an absolute encoder disc?
How is absolute resolution expressed?
Gray code or pseudo-random?
What should I send for an absolute disc quotation?
Downloads
- Absolute Encoder Disc datasheet (PDF) · available on request: sales@enc7.com
- RFQ checklist: 20 parameters to send with your drawing
Last updated 21 October 2026 · ENC7 Engineering Team