Metrohm NIRS XDS Process Analyzer – MicroBundle - Manual (Page 61)

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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.
These peak positions are not meant to be
traceable, as the wavelength calibration of the
instrument is done on an external standard, at
the sample plane, as given by ASTM and USP.
The internal wavelength standards are used to
maintain the external wavelength registration
by use of software adjustment for any
external effects on the instrument.
Select Wavelength Linearization from the
Diagnostics menu. The instrument will scan
the reference, which is the fiber optic that
runs from the monochromator to the detector
area inside the instrument.