Metrohm NIRS XDS RapidContent Analyzer - Manual (Page 42)

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Instrument matching (method transferability) requires that Reference Standardization and
Instrument Calibration be selected, and that Certified Standards are used when required to
maintain calibration. These calibrations should be run when indicated by Photometric Test
(Reference Standardization) and Wavelength Certification (Instrument Calibration).
Some of these selections are spectroscopic calibrations,
and are used to apply corrections to the instrument to
minimize differences between units of the same
configuration.
The correction programs are accessed from the
Diagnostics menu bar, shown at right. The diagnostic
steps are explained in the sections that follow.
7.1.1 Wavelength Linearization
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.
The “visible” portion of the
spectrum is similar. A
linearization is applied to this
portion of the spectrum.
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.