NPL offers a UKAS accredited service for the calibration of precision polygons. Regular polygons are examined for compliance with the NPL Specifications of Accuracy MOY/SCMI/83 (glass polygons) and MOY/SCMI/87 (steel polygons). Only Reference and Calibration grades of steel polygons are accepted for calibration. The measured errors of the exterior angles of the reflecting faces are determined by means of a precision angle indexing table, which is maintained and calibrated by NPL from first principles. Flatness and squareness of the measuring faces is also determined.

Measurement Uncertainties

The uncertainty of measurement is largely dependent on the quality of flatness of the reflecting faces. The faces should be flat to 0.05 µm in order to achieve a best measurement capability expressed as an expanded uncertainty (k=2) of ± 0.11 second of arc or better. This uncertainty is achieved by comparing each nominal angle with every corresponding angle of an NPL master indexing table.

Contact

Customer Service tel: +44 20 8943 8631
E-mail: dimensional_enquiries@npl.co.uk