Metrohm NIRS XDS Process Analyzer – SingleFiber - Manual (Page 66)

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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.
Wavelength Linearization is performed on the internal reference fiber located in the XDS Process
enclosure.
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.
Wavelength peak positions for the reference materials are located using a peak-finding algorithm.
These “found” peaks are compared to the wavelength nominals. This is done twice, one for each
direction of the grating motion. No operator interaction is required.
After the linearization is successfully sent to the instrument,
this message confirms the transfer.
Click “OK” to proceed.