A spectrometer system comprises a scanning interferometer; a drive system mechanically coupled to a movable reflector element of the scanning interferometer and operable to effect reciprocation of the movable reflector element at a plurality, preferably more than two, for example three, different scan speeds; a detector arrangement configured to sample at equidistant time intervals an interferogram formed by the scanning interferometer to generate a sampled interferogram; and a data processor is adapted to acquire a sampled interferogram at each of the plurality of different scan speeds and to perform a relative comparison of the content of the so acquired plurality of sampled interferograms.