Metrohm NIRS XDS MultiVial Analyzer - Manual (Page 34)

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The adjustment ranges from 9.5mm to 17.25mm, in adjustment steps of 0.25mm. The effective
scanned sample areas at various spot sizes are as follows:
Spot Size Minimum Sample
Diameter.* Scanned Sample Area
Diameter
(mm) Diameter
(in.) Square mm Sq. Inches
9.5 mm 11.9 mm 0.47 in. 70.9 sq. mm 0.11 sq. in.
10 mm 12.5 mm 0.49 in. 78.5 sq. mm 0.13 sq. in.
11 mm 13.8 mm 0.54 in. 95.0 sq. mm 0.15 sq. in.
12 mm 15.0 mm 0.59 in. 113.1 sq. mm 0.18 sq. in.
13 mm 16.3 mm 0.64 in. 132.7 sq. mm 0.21 sq. in.
14 mm 17.5 mm 0.69 in. 153.9 sq. mm 0.25 sq. in.
15 mm 18.8 mm 0.74 in. 176.7 sq. mm 0.28 sq. in.
16 mm 20.0 mm 0.79 in. 201.1 sq. mm 0.32 sq. in.
17 mm 21.3 mm 0.84 in. 227.0 sq. mm 0.36 sq. in.
17.25 mm 21.6 mm 0.85 in. 233.7 sq. mm 0.37 sq. in.
*Based upon 125% of beam diameter
Interpolate for spot sizes in between those listed. Areas are rounded to the digits shown.
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.