Optical absolute encoder
Hengstler ACURO AD37 optical absolute encoder
Compact safety motor feedback encoder, 29 mm deep, with 20-bit single-turn and 12-bit multi-turn resolution, ±36 arcsec accuracy and SIL 3 / PL e Cat. 3 certification, sending position and winding temperature over one cable up to 100 m.
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Select everything you need. A motor, drive and gearbox can be specified together as one axis.
Key specifications
| Speed (max) | 12,000 rpm |
|---|---|
| Temperature (max) | 120 °C |
| Resolution (max) | 32 bit |
| Accuracy | ±36 arcsec; repeatability better than ±10 arcsec |
| Interface | ACURO link (10 Mbaud, up to 100 m, single cable) |
| Safety | SIL 3 / PL e Cat. 3 |
| Resolution | 20 bit single-turn + 12 bit multi-turn |
| Vibration | up to 300 m/s² (10–2,000 Hz) |
| Shaft | 1:3 (13°) tapered shaft |
| Depth | 29 |
Summarised in our own words from Ralliant Corporation (Hengstler GmbH, part of Hengstler-Dynapar)'s published data; series maxima, individual models vary. Last checked 2026-10-30. Source 1 · Source 2
Notes on this data
Sensing principle not stated on the pages read; classed as optical in line with the ACURO range (assumption, check before publishing as fact). Supply voltage not stated.
Specify Motion is not affiliated with Ralliant Corporation (Hengstler GmbH, part of Hengstler-Dynapar). Hengstler and ACURO AD37 are used only to identify the product. Comparisons use published figures; always confirm against the current datasheet.
Hengstler ACURO AD37 replacement and alternative options
Use these supply-network options as a starting point for an engineering check. We can also help source the original Hengstler part. Published series figures do not establish an exact-model or drop-in replacement: confirm ratings, fit, interfaces and approvals for your application.
Multi-turn absolute hollow-shaft capacitive encoder that holds position through power loss, so no re-homing.
| Published maximum | ACURO AD37 | VLM |
|---|---|---|
| Resolution | 32 bit | 32 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.
Typical applications
What an optical absolute encoder is
An optical absolute encoder reads a unique code pattern on a disc or scale, so every position has its own digital value and position is known immediately at power-up. Single-turn encoders give position within one revolution; multi-turn encoders also count revolutions using gears or electronic counters. Position is sent over a serial interface such as SSI or BiSS, a manufacturer-specific protocol, or a fieldbus. Optical scanning gives high resolution, typically 17 bits per revolution or more in servo encoders, and good accuracy.
When engineers choose an optical absolute encoder
Choose an optical absolute encoder where knowing position at power-up matters, such as robots, machine tools, multi-axis machines and axes that cannot be homed safely. It removes homing routines and supports safety functions. The trade-offs are cost, interface compatibility and contamination sensitivity. Battery-backed multi-turn types need battery maintenance; gear or energy-harvesting types avoid that. In very dirty environments, magnetic or inductive absolute encoders may suit better.
How to specify the Hengstler ACURO AD37
Send these with your enquiry and an engineer can confirm the right ACURO AD37 variant or an equivalent:
- Single-turn resolution (bits)
- Multi-turn range (revolutions)
- Interface: SSI, BiSS, proprietary serial or fieldbus
- Accuracy (arcsec)
- Shaft or hollow shaft size (mm)
- Speed (rpm)
- Environment and safety rating
Common mistakes to avoid
- Choosing an interface the drive does not support
- Forgetting battery maintenance on battery-backed multi-turn types
- Confusing resolution with accuracy
- Ignoring cable length limits for serial interfaces
Hengstler ACURO AD37: frequently asked questions
Can you help replace Hengstler ACURO AD37 or source the original?
Send the full model code, quantity and required date. Our engineers can check original-part availability and assess suitable alternatives, including supply-network options where appropriate. We confirm compatibility and any changes needed before recommending a replacement.
What is the Hengstler ACURO AD37?
Compact safety motor feedback encoder, 29 mm deep, with 20-bit single-turn and 12-bit multi-turn resolution, ±36 arcsec accuracy and SIL 3 / PL e Cat. 3 certification, sending position and winding temperature over one cable up to 100 m. Published series figures include speed 12,000 rpm, temperature 120 °C, resolution 32 bit. It is made by Ralliant Corporation (Hengstler GmbH, part of Hengstler-Dynapar); Specify Motion can help source it or propose an equivalent.
Who makes the Hengstler ACURO AD37?
The Hengstler ACURO AD37 is made by Hengstler (Ralliant Corporation (Hengstler GmbH, part of Hengstler-Dynapar)) and is listed here for engineers comparing options. Specify Motion is not affiliated with Ralliant Corporation (Hengstler GmbH, part of Hengstler-Dynapar); brand names are used only to identify the product.
What is the speed of the Hengstler ACURO AD37?
The published series maximum speed is 12,000 rpm. Individual models and sizes in the ACURO AD37 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 Hengstler ACURO AD37?
We can assess suitable replacement options. On published figures, Netzer Precision VLM is options to assess from our supply network. An engineer confirms the fit against your application before recommending anything.
What is the difference between single-turn and multi-turn absolute encoders?
A single-turn absolute encoder knows its angle within one revolution. A multi-turn absolute encoder also counts complete revolutions, so it knows total position over many turns even after power loss. Multi-turn encoders avoid homing on axes driven through screws or gears.
Which interface should an absolute encoder use?
Use the interface supported by the drive or controller. SSI is simple and widely supported, BiSS-C is an open bidirectional protocol, and several manufacturer-specific protocols are common on machine tools and servo drives. Fieldbus encoders suit PLC networks. Check cable lengths and update rates for the control loop.
Further reading: Absolute vs incremental encoders · How to select an encoder · Encoders and feedback
Other optical absolute encoder series
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