Metrohm NIRS XDS RapidContent Analyzer - Manual (Page 36)

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When using the default spot size of 17.25mm,
the sample diameter should be at least
21.6mm (0.85 inch) as represented by the gray
circle in this diagram.
At the minimum spot size of 9.5mm, the
sample diameter should be at least 11.9mm
(.47 inch) as represented by the gray circle in
this diagram.
Diagrams may not be “actual size”—check dimension to verify sample size.
Set spot size in the Data Collection Method (DCM) under “Spot Size” as shown. The spot size should
generally be set to about 80% of the sample diameter for optimum illumination. (Looking at it the
other way, minimum sample size is recommended to be at least 125% of beam diameter.) Measure
the sample, and enter “Spot Size” into the DCM accordingly. Units are mm.
Once set in the DCM, and spectra are saved using this DCM, the spot size cannot be changed. This is
a safeguard to assure that all sample spectra are acquired using the same parameters. Perform
Reference Standardization with the new spot size, to have the proper reference correction.
The “Cell” must be set to “Stationary” in the DCM when using small objects. (Small objects need not
be moved across the sample window for averaging.)
Use the Iris Adapter for centering. Close the aperture
around the object to center it, then open the
aperture to avoid reflecting light back from the
aperture itself.
NOTE: Perform Reference Standardization immediately after changing the spot size,
to have the proper reference correction loaded in the instrument.