BUCHI NIRWare - Manual (Page 309)

NIRWare 1.5 Software Manual NIRWare Suite
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The Control System is designed to act as a background service in a Microsoft Windows operating system
and starts automatically when the operating system is started. The purpose of the Control System Service
is to establish the communication between the spectrometer and the PC.
The Control System tries to locate the configured instrument and establishes a connection.
6.10. System test
6.10.1. SST
The System Suitability Test is an internal system test which is performed regularly to verify the system
performance. For this purpose the NIRFlex N-500 is equipped with a standard wheel with the following
standards:

Wavelength standard (PMMA) to check the wavelength accuracy

Grey standard to check signal to noise ratio (S/N)

Four different grey standards to check the linearity
The SST consists of four different tests:
Wavenumber Accuracy
Two measurements are performed at two different wavenumbers. Both measurements must be in
between a given tolerance of 0.80 cm
-1
.
The wavenumber accuracy of the system is checked with a standard material which has well defined
peaks in the NIR range. This standard material has to be stable and must be traceable to a NIST 1920a
standard that is made of a mixture of three Rare Earth Oxide Powders.
Noise
The noise test consists of two methods, the high flux and the low flux test. The SST for noise is passed,
when the minimum and the maximum values are below a predefined tolerance.
The high flux noise is measured at approximately 100 % signal level of the instrument using a 99 %
reflective white standard (White), the low flux noise is measured at approximately 10 % using a 10 % gray
standard.
The spectrum is split into sections of 300 cm
-1
each. The peak-to-peak noise is measured for each section
and used for the calculation of the mean noise and the maximum noise at both high flux and low flux.
Linearity
The system linearity test checks if the response of the spectrometer correlates linearly with a linear signal
attenuation.
3 wavenumber positions are used during an SST; 5000 / 6250 / 8330 cm
-1
The actual absorbance at each wavenumber position (= measured absorb.) are compared with max.
reference values (= Reference Absorb.).
These measurements are done using 5 different gray filters.
The deviation to the reference value as well as the interception are checked.