AL228 + SC20 · Compact absolute feedback
AL228 Compact Absolute Magnetic Linear Encoder
Absolute position feedback for motion assemblies where every millimetre matters.
The AL228 pairs a 28 × 14 × 10 mm magnetic readhead with the matched SC20 coded magnetic scale. It delivers non-contact, battery-free absolute linear measurement over travel up to 2 m, with selectable 0.1, 0.5 or 1 µm resolution.
Choose BiSS-C, SSI or an RS-485 protocol option to match your controller.
Designed around available space
Compact absolute feedback for positioning stages and automation axes
AL228 is a compact absolute linear encoder for space-constrained motion assemblies. The separate readhead and magnetic scale let you integrate feedback alongside an axis while retaining access to the mounting points and cable.
Small readhead footprint
A 28 mm body and two M3 mounting positions at 20 mm pitch suit compact positioning stages and automation axes. Check the cable route and recommended air gap in your assembly.
Battery-free position sensing
The coded SC20 scale provides the absolute position reference without a backup battery. Specified absolute-position startup time is less than 400 ms.
Controller-matched feedback
Select resolution and one communication variant when ordering. BiSS-C, SSI and RS-485 protocol options support different control architectures; confirm the exact format before integration.
AL228 technical specifications
Choose the resolution, protocol and matched scale as one feedback system. Resolution describes the position increment; it does not state the accuracy of the installed axis.
| Parameter | AL228 specification |
|---|---|
| Measurement principle | Non-contact, battery-free absolute magnetic linear measurement |
| Matched scale | SC20 absolute code track + incremental track |
| Readhead dimensions | 28 × 14 × 10 mm |
| Resolution options | 0.1 µm / 0.5 µm / 1 µm |
| Maximum measuring travel | 2 m |
| Repeatability | Within ±1 µm at 1 µm resolution and 0.3 mm sensing gap |
| Positioning accuracy | ≤30 µm, module-dependent; confirm the required system accuracy with the selected scale |
| Maximum linear speed | 10 m/s |
| Position update time | <5 µs during communication; end-to-end controller latency is not specified |
| Absolute-position startup | <400 ms |
| Supply / no-load current | 5 V DC ±5%; <120 mA at 25°C |
| Sensing gap | Recommended 0.30 ±0.10 mm; maximum specified ≤0.8 mm |
| Mounting / indication | 2 × M3 at 20 mm pitch; LED indication |
| Protection | IP67 readhead housing |
| Cable / termination | 0.5 m standard; up to 10 m available; flying leads, DB9 or DB15 male |
BiSS-C, SSI and RS-485 interface options
Order one communication variant for your AL228 readhead. BiSS-C and SSI use differential RS-422 signaling; RS-485 variants use the protocol and data format selected for the controller.
| Ordered protocol option | Electrical signaling | Specified rate / data format |
|---|---|---|
| BiSS-C | Differential RS-422 | Clock up to 10 MHz; 26 effective position-data bits |
| SSI | Differential RS-422 | Clock up to 250 kHz; 26 effective position-data bits |
| Modbus RTU | RS-485 | Baud rate up to 256 kbit/s |
| Tamagawa-compatible format | RS-485 | 2.5 Mbit/s; 24-bit format |
| Panasonic-compatible format | Confirm for ordered variant | 48-bit format listed; confirm timing and electrical interface |
Cable and connector
Choose flying leads, a DB9 male connector or a DB15 male connector. The standard cable is 0.5 m; lengths up to 10 m are available.
Wiring confirmation
Obtain the wiring drawing for the ordered variant before applying power. Connector pin assignments are not defined in the product specification.
Communication timing
Confirm clock or baud rate, data format, cable length and signal integrity together. Data-field width does not increase the specified 2 m travel or define positioning accuracy.
Readhead dimensions and SC20 magnetic scale installation
Mount AL228 with the two M3 positions and maintain a recommended 0.30 ±0.10 mm assembly air gap. Align the readhead with the absolute and incremental tracks as shown, then verify the counting direction and full-travel behavior in the final assembly.
Matched SC20 absolute magnetic scale
Use the SC20 coding and track layout specifically matched to AL228. Generic scale-family pole pitches and supply lengths do not imply interchangeability.
- Scale operating temperature: 0 to +50°C.
- Maximum relative humidity: 95%, non-condensing.
- Minimum bend radius: 100 mm.
- Thermal expansion coefficient: approximately 16 × 10⁻⁶ K⁻¹.
- AL228 effective measuring travel remains ≤2 m.
For other magnetic tape requirements, see the magnetic linear scale and encoder tape collection.
Adhesive mounting sequence
- Thoroughly clean the mounting surface.
- Remove the magnetic scale backing liner and press the scale firmly into position.
- Clean the exposed scale surface.
- Remove the cover-foil backing liner, then press the foil firmly onto the scale.
- Secure the cover-foil ends against lifting and fit end caps where supplied.
Keep the coded scale away from strong magnets and magnetic objects. Maintain the minimum bend radius during handling. Once bonded, the scale cannot be removed intact and reused. Confirm mounting torque, allowable angular alignment and cable bend radius for your installation.
Compare OTV absolute magnetic linear encoder series
Choose AL228 when readhead size and integration space are the main constraints. For longer travel or a larger installation gap, compare the other OTV series.
| Series | Primary selection need | Resolution | Travel / distinguishing specification |
|---|---|---|---|
| AL228 | Compact motion assemblies | 0.1 / 0.5 / 1 µm | Up to 2 m; 28 × 14 × 10 mm readhead |
| AL200 | Fine-resolution feedback over longer axes | Down to 0.1 µm | Up to 16 m |
| AMG | Long-travel absolute feedback | 1 µm | Up to 82 m |
| AL500 | Larger mounting clearance | 1 µm | Mounting gap up to 1.6 mm |
Explore the absolute magnetic linear encoder range for the wider product selection. Confirm the final interface, scale and performance specifications for each ordered system.
AL228 compact encoder FAQs
How small is the AL228 magnetic linear encoder readhead?
The readhead envelope is 28 × 14 × 10 mm. It mounts at two M3 positions with a 20 mm pitch. Allow space for the cable and maintain the recommended 0.30 ±0.10 mm sensing gap.
Is AL228 suitable when I need a miniature absolute linear encoder?
AL228 is an option for compact assemblies that can accommodate its 28 × 14 × 10 mm readhead and separate SC20 scale. Check the available space, travel up to 2 m, required accuracy and controller interface against your design.
Does AL228 need a backup battery?
No. AL228 reads absolute position from the coded magnetic scale without a backup battery. The specified absolute-position startup time is less than 400 ms.
Does 0.1 µm resolution mean 0.1 µm positioning accuracy?
No. Resolution, repeatability and positioning accuracy are separate specifications. AL228 offers 0.1, 0.5 and 1 µm resolution options; installed performance also depends on the matched scale, travel, temperature and mounting conditions.
Can AL228 measure 50 m with a long SC20 scale?
No. The AL228 encoder system is specified for measuring travel up to 2 m. General SC20 supply-length options do not extend this travel. For longer axes, compare AL200 or AMG.
Can one readhead switch between SSI, BiSS-C and RS-485?
Select one protocol option for the ordered readhead. Confirm the controller format, electrical interface and wiring drawing with OTV Sensing; do not assume that every variant supports every protocol.
Configure your AL228 + SC20 system
Request an AL228 encoder quote
Tell us your measuring travel, target accuracy, resolution, controller and protocol, cable length, termination and available mounting space. OTV Sensing will confirm the matched readhead, scale layout and wiring requirements.
Specifications: AL228 / SC20 Product Specification, OTV-AL228-SPEC-001, Revision 1.0, 4 November 2026. Configuration and installed system performance are subject to confirmation.