We received an enquiry recently from a customer integrating an absolute encoder directly onto a brushless servomotor shaft, where panel space was very tight and they didn’t want to add much length to the motor. This is a common request, and the Hengstler ACURO AD34 was built exactly for this situation.
This looks simple, but the AD34 isn’t a bolt-on encoder like the ones on separate shafts we usually quote – it’s a hollow-shaft, blind-hollow-shaft style unit that mounts straight onto the “B” end of the motor shaft. All it needs is a 6 mm centre bore machined into the shaft end. The notched shaft on the AD34 press-fits into that bore in one operation, and a flexible torque support (not a rigid coupling) takes up the small amount of shaft misalignment that’s always present on a servo motor. Installation depth is only 25 mm for the single-turn version and 34 mm for the multi-turn version, so it fits into motors where a conventional encoder housing simply won’t.
In actual application, the AD34 gives up to 22-bit single-turn plus 12-bit multi-turn resolution, so it can track both fine position within one revolution and the total number of revolutions – useful for servo axes that need absolute position on power-up without a homing move. It runs on SSI or BiSS digital interface, handles continuous speeds up to 10,000 rpm, and is rated for +120°C operating temperature, which covers most motor housings that run hot under load.
From our experience, before we quote this, we would normally check the exact motor shaft diameter and whether it’s prepared for the 6 mm bore, the interface your servo drive expects (SSI or BiSS), and the ambient/motor surface temperature at the mounting point. Hope this helps.
