Calibration Transfer between FTLA2000 and MB3000 systemsAppendix E FTIR Frequency scale calibration
72 AA003700-01 rev. G. 2.0
When using the vial accessory with an FTLA, the mean frequency is significantly
shifted compared with open beam. The mean frequency is now 7300.06 cm
-1
.
In conclusion the MB3600 has better controlled illumination that is closer to
circular symmetric than the FTLA. It provides for better control of frequency
calibration and a more symmetrically defined line shape. However, when
transferring calibrations from an FTLA to an MB3600, there is a need for redefining
the measured calibration frequency for the water vapor calibration test. The
redefinition of the water vapor frequency requires a change in interpolation as well
as a change in frequency assignment to insure that discrete spectral data points align
with data points from other spectra. The redefinition of frequency is best determined
by the Toluene reproducibility test where spectra are shifted until the Toluene
spectrum is reproduced most precisely.
Frequency redefinition requires a specific software module that is available from
ABB.
Figure E- 8. Illumination distribution as a function of frequency for figure 7
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