Metrohm NIRS XDS Process Analyzer – MicroBundle - Manual (Page 72)

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The NIR 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,
traceable to NIST.
The internal wavelength materials 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.
The instrument operates for a minute or two, while the linearization is performed. No intervention is
required form the operator during this time.
After the linearization is successfully sent to the instrument,
this message confirms the transfer.
Click “OK” to proceed.
10.3.2 Reference Standardization, Interactance Immersion
Reference Standardization is a method to provide a virtual 100% reflectance reference at each data
point, to serve as a true spectroscopic reference with no character attributable to the physical
reference that is used. In a process environment, this will minimize differences between the sample
fiber lengths, and to the internal reference fiber. Reference Standardization is important to achieve a