Hollow-shaft absolute encoder selection

Establish the usable mechanical envelope

Give the shaft or clear-bore diameter, outer diameter and axial space. Identify whether the application needs a bearing-supported encoder or an integrated ring-and-readhead arrangement. An encoder bore does not replace the load bearings, and the encoder should not be assumed to carry external shaft loads.

For a hollow-centre joint, reserve space for cables, optics, fluid passages or a slip ring. Tolerances, installation access and cable exits can reduce the available envelope. Send a section drawing if possible so the actual assembly can be discussed.

Separate resolution from accuracy

Resolution describes the reported position increment. Accuracy concerns the relationship to the true position, while repeatability concerns returning to the same result. Mounting eccentricity, runout, tilt and temperature can affect the installed result even when the electrical output has a high bit count.

Read the resolution, accuracy and repeatability guide before specifying performance only in bits. State the allowable error at the load and the motion speed, rather than relying on an encoder headline.

Check the absolute interface

SSI and BiSS, for example, are not labels that make all implementations interchangeable. Confirm supply voltage, data format, timing, cable and connector, controller support and any alarm or diagnostic bits. Single-turn absolute position and multi-turn tracking serve different requirements; state what must be known after power returns.

The existing Netzer VLP catalogue entry is one hollow-shaft range with published interface and resolution information. Its family maxima are not the ratings of every size. Consult the exact model information for dimensions, accuracy and interface details.

Installation and environmental questions

Describe temperature, vibration, contamination, available shielding and the mounting materials. A design using an open encoder inside a sealed joint has different responsibilities from one using a separately housed encoder. Protection belongs to the complete specified arrangement.

Send the usable bore, envelope, required installed accuracy, rotational speed, controller and preferred interface. We can discuss the encoder alongside a frameless motor, drive and rotary connection where relevant. Final selection requires the exact mounting and electrical configuration to be checked.