Influence of the Order of Averaging and FFT on FTIR Measurements

Fourier Transform Infrared Spectrometers are based on the principle of Michelson interferometry. Here, one interferometer mirror is moved and the intensity of the interfering beams is recorded as a function of the path length difference between both arms. To increase the signal to noise ratio of a measurement several hundreds of such scans are averaged. Common practice calculates a spectrum from this mean interferogram. In case of certain differences between the individual interferograms, e.g. due to intensity changes of the light source, mechanical vibrations or changes in the background signal, this procedure can be disadvantageous. The influence of this issue on the spectroscopic data quality measured at a Bruker IFS125 is determined. The possibilities and necessity of changing this procedure are evaluated.