Metrohm Vision – Diagnostics - Manual (Page 38)

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Auto-linearization will maintain correct wavelength registration.
On instruments using fiber-optics (and certain other models) Wavelength Linearization cannot use the
2306.1 peak due to attenuation in the fiber-optics. Vision will perform the linearization using peaks
available within the useable wavelength range of the instrument.
9.2 Wavelength Linearization on XDS Instruments
Wavelength Linearization for XDS instruments should only be performed at setup, after a lamp
change, or after instrument repair and then followed by Reference Standardization, Instrument
Calibration, Performance Test, and IPV Setup. Running Wavelength Linearization after Instrument
Calibration can interfere with the alignment obtained under Instrument Calibration.
Wavelength Linearization uses an internal wavelength standard set to determine a set of internal,
arbitrary peak positions that the instrument will use to maintain repeatability of wavelength response.
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 for the
wavelength axis.
The “visible” portion of the spectrum is similar.
A linearization is applied to this portion of the
spectrum as well. Minor artifacts appear in these
raw spectra due to detector crossover and other
spectroscopic reasons. After linearization these
artifacts are minimal or not evident, some being
beyond the usable range of the instrument.
These peak positions are not meant to be traceable, as the wavelength calibration of the XDS
instrument is done on an external standard, traceable to NIST. The internal wavelength standards are
used to maintain the external wavelength registration by use of software adjustment for any external
effects on the instrument.