Metrohm NIRS XDS MasterLab Analyzer - Manual (Page 37)

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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.
NOTE: Perform Reference Standardization immediately after changing the spot
size, to have the proper reference correction loaded in the instrument.
Each time the spot size is changed, whether manually or by selecting a DCM, the
Reference Standardization must be repeated.
See section 7.1.2 for Reference Standardization in Tablet Transmission.
See section 8.1.2 for Reference Standardization in Reflectance.
5.4 Use of the Sample Transport Mechanism
The sample transport uses motors and lead screws to
position tablet or vial trays over the sampling
window of the module, as shown in the photo at
right. (A vial tray is shown.)
The user must select the correct tray configuration
(number of sample positions) and select which of
those positions will be sampled. The detector type –
reflectance or transmission – is selected in the Data
Collection method (DCM).