Metrohm NIRS XDS Process Analyzer – DirectLight/NonContact - Manual (Page 108)

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2. Select the channel to be used for the test.
In this case, we select “SAMPLE”. The end
of the Interactance Immersion probe
should be protected from stray light for
this test.
This tests the sample channel, and provides
a comprehensive test of instrument
performance.
11.6 Direct Light Probe
The Direct Light Probes require special methods of calibration. The lamp is mounted in the probe and
a fiber bundle carries reflected light from the sample to the instrument to be broken down in the
monochromator to individual wavelengths, and then measured for spectral response. Absorbance of
the sample is then determined.
NOTE: Please observe that the Direct Light option only works with Vision 3.5 and above.
11.6.1 Wavelength Linearization, Direct Light Probes
The first test to be run is Wavelength Linearization. This provides initial wavelength locations for the
sample spectrum, prior to final wavelength calibration.
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 material on the sample paddle
located in the XDS Process enclosure.
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.)