Metrohm NIRS Analyzer PRO - Manual (Page 66)

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6. To see the test results and acceptance
specifications, click on the “OpQual” tab at
the bottom of the screen. This is a typical
result.
7. If a printed copy is needed, click on “Print
Report”.
A copy is automatically saved to the Vision
Diagnostic Database. Click on “Close Report”
when finished.
13.3.2 Reference Standardization (External Reference Correction)
Reference Standardization is a method to set the photometric scale of the instrument to a known,
repeatable level. Ideally, the instrument reference scale should be set so that 100% reflectance is
equivalent to zero (0) Absorbance. This facilitates transfer of models from one instrument to another
of the same optical sampling geometry.
In the case of the Analyzer PRO Direct Light System this method is not practical for a variety of
reasons, including operating distance, possible window reflections, temperature variations, and other
optical factors. Instead, the Direct Light system is standardized on a special 99% Spectralon®
standard. Once standardized, the system will maintain its settings for the life of the lamp, and should
remain very stable. The Spectralon standard should be kept in a protected, clean location, so it will be
ready when required at the next lamp change or major service interval.
Fortunately, NIR instruments normally use mathematical and chemometric modeling methods that
compensate for minor photometric scale differences between instruments. This permits consistent
spectral readings between like systems. The method for Direct Light is called “ERC” for External
Reference Correction”.
Because this function is performed at the factory, it is not covered in this manual. If you have a
Analyzer PRO Direct Light System, please contact your local Metrohm office for more information on
External Reference Correction.