Qstick User Manual
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can set a maximum exposure time in order to prevent very long exposure times in cases
when there is simply no signal.
Spectra can be taken with or without spectral sensitivity correction (see chapter 3.9 for
more details). If the lightmeter button [ ] is selected, the spectral sensitivity of the
spectrometer is automatically corrected and the intensity axis is measured in nW/nm.
PLEASE NOTE:
If you take a spectrum with spectral sensitivity correction, the noise in the
spectrum is not evenly distributed, because some parts of the spectrum are more
amplified than others. On the other hand, if this button is not selected, the spectral
sensitivity is not corrected and the intensity axis displays values as they are produced by
the spectrometer hardware. In this case, you may find an uneven distribution of the
sensitivity across the spectrum. For precise measurements, it is recommended to turn on
spectral sensitivity correction.
Dark spectra for the spectrometer are stored in the device and used automatically when
taking spectra (see chapter 3.9 for details). If you have background radiation, you can
compensate for it by taking a background spectrum (see chapter 3.8). In the Exposure
Toolbar you can also select the triggering mode and choose a reference spectrum for
absorption, reflection and transmission spectroscopy (see chapter 3.8).
3.4
Spectrum Display
The Main Diagram Panel displays all spectra that are marked by a check mark in the
Spectrum List. If no spectrum is checked in the list, then the currently selected spectrum
(marked by a gray bar) is displayed. You can check and uncheck all spectra at once by
clicking on the corresponding button [ ] or [ ] on top of the Spectrum List.
The peaks in the spectra are automatically determined. This not only works pretty reliable
for clearly defined peaks, but also for those lying in the side of another peak or those that
are just above the noise level. If necessary, you can fine-tune the parameters for finding
the peaks by choosing ‘‘Peak Finder Parameters’’ from the Tools menu. In this window
you can choose three settings:
o
‘‘Absolute threshold’’ determines how much a peak must be above the noise level
in order to be considered as a peak.
o
‘‘Relative threshold’’ describes how large a peak must be compared to the local
minima before and after it in order to be considered as a peak.
o
‘‘Position threshold’’ determines how much of the top part of the peak is
considered when calculating the peak position.
Peak positions and widths are only displayed for the currently selected spectrum. The
peak positions, heights and widths are also displayed in the Properties Panel and can be
exported by choosing ‘‘Export Peaks’’ from the File menu.
In the Display Parameters Panel below the diagram you can select how the spectra are
displayed. These settings affect the diagram display, but do not modify the actual data.
Here you can change the scaling of both axes, the unit of the wavelength axis, turn the
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