Magnetic rotary encoder
RLS AksIM-2 magnetic rotary encoder
Off-axis absolute magnetic kit encoder for hollow shafts, with up to 20-bit resolution, ±0.004° to ±0.020° accuracy after self-calibration, 10,000 rpm and ring inner diameters from 8 to 68 mm.
Key specifications
| Speed (max) | 10,000 rpm |
|---|---|
| Bore (min) | 8 mm |
| Inner diameter (max) | 68 mm |
| Temperature | -40–105 °C |
| Data / bus | BiSS C, SSI, asynchronous serial |
| Supply | 4.5–5.5 V |
| Resolution (max) | 20 bit |
| Accuracy | ±0.004° to ±0.020° (±14 to ±72 arcsec) after self-calibration |
Summarised in our own words from RLS Merilna tehnika d.o.o. (Renishaw associate company, 50 % owned by Renishaw)'s published data; series maxima, individual models vary. Last checked 2026-10-30. Source 1
Specify Motion is not affiliated with RLS Merilna tehnika d.o.o. (Renishaw associate company, 50 % owned by Renishaw). RLS and AksIM-2 are used only to identify the product. Comparisons use published figures; always confirm against the current datasheet.
Typical applications
Alternatives that meet or exceed these figures
Engineers often come to us with a RLS part number and leave with an alternative that is easier to source, quicker to deliver or a better fit for the machine. These 3 series from our supply network are the closest match on published figures.
Absolute magnetic sensing head for linear and rotary scales, with a multi-turn MT variant; tiny FFC or Molex packages.
| Published maximum | AksIM-2 | AKS16 / AKS16-MT |
|---|---|---|
| Resolution | 20 bit | 20 bit meets or exceeds |
Highest-resolution Bogen absolute head, 21 to 24 bit, for linear and rotary scales.
| Published maximum | AksIM-2 | AKS17 |
|---|---|---|
| Resolution | 20 bit | 24 bit meets or exceeds |
Open PCB-style absolute head (IP00) at 18-20 bit for integration into OEM assemblies.
| Published maximum | AksIM-2 | AKP18 |
|---|---|---|
| Resolution | 20 bit | 20 bit meets or exceeds |
Figures are the highest published for each series and are not always measured the same way. A higher figure is not automatically a better choice: mounting, duty cycle, feedback, connectors and approvals matter too. An engineer will check the fit against your application before recommending anything.
What a magnetic rotary encoder is
A magnetic rotary encoder measures angle by sensing the field of a magnet with Hall-effect or magnetoresistive sensors. On-axis designs place a diametrically magnetised magnet on the shaft end above a sensor chip; off-axis designs read a multi-pole magnetic ring around a hollow shaft. Signal processing turns the field into absolute or incremental position. Because there is no optical path, magnetic encoders tolerate dust, oil, moisture and vibration, typically with moderate resolution and accuracy at low cost.
When engineers choose a magnetic rotary encoder
Choose a magnetic rotary encoder for robust, compact feedback in harsh or cost-sensitive applications, such as motors, AGVs, robotics, agricultural and mobile machinery. Off-axis rings suit hollow joints. The trade-offs are accuracy and magnetic interference: accuracy is typically lower than optical, and strong stray fields from brakes or motors can affect the reading. For high precision, choose optical. Consider shielding and mounting tolerances carefully.
How to specify the RLS AksIM-2
Send these with your enquiry and an engineer can confirm the right AksIM-2 variant or an equivalent:
- Resolution (bits or counts)
- Accuracy (degrees or arcmin)
- Absolute or incremental output
- On-axis or off-axis ring mounting
- Interface: SSI, BiSS, SPI, PWM or analogue
- Mounting tolerances: gap and runout (mm)
- Environment and IP code
Common mistakes to avoid
- Mounting near brakes or motor magnets without shielding
- Exceeding the allowed air gap or runout
- Expecting optical accuracy from a magnetic encoder
- Overlooking calibration after installation
RLS AksIM-2: frequently asked questions
What is the RLS AksIM-2?
Off-axis absolute magnetic kit encoder for hollow shafts, with up to 20-bit resolution, ±0.004° to ±0.020° accuracy after self-calibration, 10,000 rpm and ring inner diameters from 8 to 68 mm. Published series figures include speed 10,000 rpm, bore 8 mm, inner diameter 68 mm, temperature -40 °C. It is made by RLS Merilna tehnika d.o.o. (Renishaw associate company, 50 % owned by Renishaw); Specify Motion can help source it or propose an equivalent.
Who makes the RLS AksIM-2?
The RLS AksIM-2 is made by RLS (RLS Merilna tehnika d.o.o. (Renishaw associate company, 50 % owned by Renishaw)) and is listed here for engineers comparing options. Specify Motion is not affiliated with RLS Merilna tehnika d.o.o. (Renishaw associate company, 50 % owned by Renishaw); brand names are used only to identify the product.
What is the speed of the RLS AksIM-2?
The published series maximum speed is 10,000 rpm. Individual models and sizes in the AksIM-2 range vary, so check the exact variant against your duty cycle, mounting and environment, or ask our engineers to confirm the right size for you.
Is there an alternative to the RLS AksIM-2?
Yes. On published figures, Bogen AKS16 / AKS16-MT and Bogen AKS17 are the closest match from our supply network. An engineer confirms the fit against your application before recommending anything.
Are magnetic encoders as accurate as optical encoders?
Typically not. Magnetic encoders tolerate contamination and vibration well but usually have lower accuracy and resolution than optical encoders of similar size. Self-calibration and good mounting can improve results. For high-precision positioning and metrology, optical encoders remain the usual choice, while magnetic types win on robustness and cost.
What is the difference between on-axis and off-axis magnetic encoders?
On-axis encoders read a single magnet on the end of a shaft, which is simple and compact. Off-axis encoders read a magnetic ring around a shaft, which leaves the centre free for hollow shafts or cables. Off-axis designs are more sensitive to mounting tolerances.
Further reading: Magnetic vs capacitive vs optical encoders · How to select an encoder · Encoders and feedback
Other magnetic rotary encoder series
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