Metrohm NIRS XDS Process Analyzer – DirectLight/NonContact - Manual (Page 94)

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Information about the WST3Wxxx Transmission Wavelength Calibration Standard:
The transmission wavelength standard
used is traceable to NIST SRM-2035,
through
direct comparison on the Metrohm
Master Transmission Instrument.
The optical materials used in the
WST3Wxxx Calibration Standard have
very sharp bands, which are found to
be stable and repeatable.
The Master Instrument was first calibrated using
SRM-2035, and the resulting peak positions of the
WST3Wxxx standard were determined. Each
calibration standard is verified for correct response
prior to shipment. The correlation of the
calibration standard to SRM-2035 is checked on a
regular basis to assure consistent response.
The XDS instrument is set to predetermined
nominals during Instrument Calibration, since
these are the best-known information for NIR peak
wavelengths.
In Wavelength Certification, the NIST-stated
uncertainty of 1.0nm is applied.
11.4.5 Window Correction, Transmission Probes
Window Correction is a method to permit the user to calibrate the fiber optics using a calibration
fixture. Next, the fibers are inserted into the barrels, and the optical differences are mapped. This
gives a clear, repeatable measure of the optical difference between the two geometries.
This window correction method offers a large
advantage to users running with probe barrels
permanently installed in a reactor or other vessel.
At initial set-up, the window difference is
measured and stored in Vision.
At periodic maintenance intervals, the fiber optic
bundles can be removed from the barrels, which
are now permanently installed
The instrument and fiber optics can be calibrated for wavelength and Reference Standardized
response, without using the Transmission Probe barrels. After this is done, the fiber optic bundles are
put back into the permanently installed barrels, and the Window Correction is re-applied. This assures