Using the Spectrometer . 63
You should keep the sample compartment closed during routine operation to prevent the
water vapor and oxygen from entering. When performing operations within the sample
compartment, do not leave the sample compartment cover open for any longer than is
necessary. After closing the sample compartment, purge for several minutes before starting
measurements.
When the spectrometer has been standing for some time unpurged, an initial flow of
20 L/min is recommended. After the spectrometer has been thoroughly purged, the flow can
be reduced to 6–7 L/min.
When you have a good deal of work in a spectral region where water vapor or oxygen
absorb the radiation, we recommend that you purge the spectrometer more or less
continuously. This has the advantage that startup times are markedly shorter. This
advantage is somewhat offset by the increased consumption of nitrogen.