An international length comparison at an industrial level using a photoelectric incremental encoder as transfer standard

Abstract A Japanese–German interlaboratory comparison of length measurements was conducted. A photoelectric incremental encoder with a measurement length of 270 mm was used as transfer standard. An agreement of better than 27 nm over the entire length was ascertained, and the “short-range” deviations within a length interval of approximately 10 mm could be characterized with a standard deviation of σ=0.8 nm. The results attained are considered as consistent with the estimated uncertainties of measurement. Since the measurements performed are directly traceable to the SI unit of the “metre”, the comparison supports ideas currently being discussed by some National Metrology Institutes and dealing with the question of how foundations can be laid for a generally accepted application of this method of traceability.