Metrohm NIRS Analyzer PRO - Manual (Page 60)

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9. Vision asks to upload the
ERC to the instrument for
use when taking spectra.
Click “OK”.
10. When finished, Vision
indicates that the
correction was properly
loaded to the instrument.
If a printed copy is
needed, click on “Print
Report”.
The plots on this diagram
bear further explanation to
help the user understand
what is taking place.
The magenta plot at the
bottom is a raw
absorbance spectrum of
the internal reference fiber
of the instrument. This
should not be used as a
reference in this form, for
two reasons:
First, the absorbance is negative, which means the reference would appear artificially brighter than
samples. Second, the spectral shape is not a flat line, and would impart unwanted artifacts into the
sample spectrum. Correction is required.
The cyan (light blue) spectrum is the Certified 99% Reflectance Standard, as measured on a
controlled, calibrated master spectrophotometer. This is close to 100% reflectance, though not
exactly. By measuring on the master instrument, the difference between the instrument reference
fiber and the Certified 99% Reflectance Standard is calculated, and is stored for correction purposes.
The correction between the Certified 99% Reflectance Standard and the instrument reference fiber is
applied. This correction is the green spectrum at the top of the plot. When this correction is applied,
the resulting spectrum is the purple line, overlaying the cyan plot of the Certified 99% Reflectance
Reference.
Vision also applies the mathematical correction required to make the instrument reference read at