Buchi NIRMaster Essential, Руководство по эксплуатации

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Büchi Labortechnik AG
Operation | 6
Operation Manual NIRMaster™ 25/46
u
Mind the ambient temperature data as listed in Chapter 3.6.2 "Ambient
conditions", page 16
Precondition:
R If temperature is too low:
u
Let system warm up sufficiently.
Precondition:
R If temperature is too high:
u
Clean filters and provide sufficient airflow.
6.2.2 NIR linearity test
The linearity of the NIR detector is tested by presenting five filters with known
absorbance to the instrument. The measured absorbance is compared to the known
reference value.
To pass this test, all absorbance factors must be within the tolerance.
6.2.3 Signal-to-noise ratio determination
With this test the ratio of signal power to noise power is determined. A high flux
(maximum intensity) and a low flux (10 % intensity) beam is being analyzed for a
number of wavenumber intervals.
To pass these test, the average and the minimum values must be within the
tolerance.
6.2.4 Wavenumber stability test
The wavenumber stability of the instrument is checked by presenting a PMMA filter
to the instrument. The measured spectra is compared to a known reference spectra.
To pass the test the measured spectra should be within the wavenumber tolerance
limits of the reference spectra.
6.3 Reference measurements
Frequent reference measurements compensate for environmental effects, which
might influence the spectra. A combination of internal and external reference
measurements provides best result quality and measurement stability.
6.3.1 External reference
NOTE
External referencing needs user interaction.
In order to measure the reflectance of a sample, the measured intensity spectrum of
the sample is divided by a reference spectrum. The reference spectrum is generated
by a white standard in the sample position.
See Chapter 6.3.3 "Performing a reference measurement", page 26.
6.3.2 Internal reference
NOTE
Internal referencing is performed by the instrument automatically.