We had an enquiry from a customer designing a small servo axis where there simply wasn’t room for a normal encoder housing behind the motor – every extra millimetre of shaft length was a problem for their machine layout. This is exactly the situation the Hengstler ACURO AD35 was designed for.
This looks simple, but “shortest hollow-shaft encoder in the world” is a real spec here, not just a marketing line – the AD35 only needs 23.65 mm of mounting depth behind the motor. It’s a single-sided 8 mm hollow-shaft design that slides straight onto the motor shaft end, supported by dual ball-bearings and a flexible torque support so it isn’t fighting shaft misalignment. The housing is plastic to keep weight and inertia down, which matters on a fast-spinning servo shaft.
In actual application, the AD35 gives up to 22-bit single-turn resolution (it’s single-turn only – there’s no multi-turn version in this series), runs on SSI or BiSS digital interface, handles continuous speeds up to 10,000 rpm, and is rated for +120°C operating temperature. It’s built for high-speed, space-constrained servo applications rather than general industrial shaft mounting.
From our experience, before we quote this, we would normally check the motor shaft diameter (8 mm hub), whether your application needs single-turn position only or absolute position across multiple revolutions (if it’s the latter, the AD34 hollow-shaft or a separate multi-turn model would suit better), and which interface your controller expects. Hope this helps.
