Glass Encoder Disc Selection: A Practical Checklist

Start with the instrument function

State whether the disc provides incremental position, an absolute code, an index reference or a combination of these functions. The readhead arrangement and the required output determine the useful pattern layout before the glass geometry is finalized.

Define the reading geometry

Provide the outside diameter, bore, active track radius, track count, reference marks and viewing side. For a linear or angular requirement, identify the reading radius or scale pitch so the pattern can be evaluated against the actual instrument geometry.

Separate resolution from accuracy

Line count or code-track density describes the available position intervals. It does not by itself establish installed accuracy. Keep pattern pitch, eccentricity, datum position, readhead alignment and system verification as separate requirements in the drawing.

Specify the acceptance record

List the critical dimensions, pattern placement, optical contrast, surface condition and inspection method. Include the drawing revision, part or lot identifier and any required measurement map so the delivered component can be checked against the same references.

Link the drawing to the inquiry

Attach the current DWG with units, film-side orientation, datums and revision. Add the application, prototype quantity and target delivery date. A short, complete brief lets the technical review focus on the few choices that affect the encoder design.

Using this guide

This encoder-disc inquiry checklist brings the application, reading geometry, track definition and acceptance records into one specification.

Use it before ordering; the linked guides explain coding, error sources and numerical conversions in more detail.

Which dimensions are needed beyond outside diameter?

Specify bore or locating datum, reading radius, track count and widths, thickness and pattern position relative to the mechanical datum, using the actual head and mounting design.