Traceable 28 m-long metrological bench for accurate and fast calibration of distance measurement devices

An interferometric bench with 28 m length has been realized at INRiM (Istituto Nazionale di Ricerca Metrologica). The facility is mainly devoted to calibrating electronic distance-measurement devices and absolute interferometers. Two working operating modes are possible: a fringe-counting mode having an uncertainty of U = root(0.07)(2) +(0.013 .L)(2) mu m, where L is the measured length in meters, and a 'Doppler' mode having an uncertainty of U = root(0.02)(2) +(0.1 .L)(2) mu m, the latter allowing measurements at high carriage speed. These uncertainty budgets do not take into account the effect of the air refractive index, which has been evaluated separately on the basis of the Edlen formula leading to a relative uncertainty contribution equal to 3 x 10(-7). An accurate motor control allows speeds from a few micrometers per second up to 2.7 m s(-1), making the device also suitable for the calibration of speed measurement devices.