EUROMET comparison: diameter of small ring gauges

Comparison measurements of the diameter of small ring gauges (0.1 mm to 1 m m) were carried out by six European national metrology institutes (NMIs). T he participants applied different measurement principles: mechanical contac ting measurement and optical measurement with respect to the projection of the inner diameter or with respect to the position of the cylinder edges. T he uncertainties associated with the diameter measurement results vary cons iderably among the different participants, from U = 0.10 mum to U = 5 mum. In general the measurement results agree within their associated uncertaint ies, with the exception of the optical measurements of the position of the cylinder edges which exceed the reference values by between 10 mum and 30 m um, probably because of the lacerated edges of the ring gauges.