Metrohm NIRS XDS Process Analyzer – DirectLight/NonContact - Manual (Page 74)

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11.2.1 Wavelength Linearization, Interactance Immersion
The first test to be run is Wavelength Linearization. This provides initial wavelength locations for the
sample spectrum, prior to final wavelength calibration. Wavelength Linearization is performed on the
internal reference fiber located in the XDS Process enclosure.
Wavelength Linearization uses internal wavelength materials to determine a set of internal, arbitrary
peak positions that the instrument will use to maintain repeatability of wavelength response.
The wavelength positions of these peaks appear as shown.
The scale of this display is marked in encoder pulses, which do not relate to nanometers directly.
From the peaks, a linearization is performed, which allows assignment of nanometer values. (Actual
spectral shape depends on fiber configuration.)
The spectrum shown above does not exhibit any noise effect from fiber attenuation. Actual fiber
optic probe spectra will exhibit noise at the lower and upper ends of the spectrum, based upon
length of fiber used. This is normal.
A Wavelength Linearization is performed in the forward direction of grating scan, then again in the
return direction. The resulting information is adjusted by Vision into one corrected spectrum.