12
Apr-09
Avantes
www.avantes.com
1.3
Measuring and saving a spectrum
1. After starting AvaSoft, the green Start button needs to be clicked to start measuring.
2. Connect a fiber or probe to the light source and to the spectrometer input port(s) and set up the
experiment for taking a reference spectrum.
3. Adjust the Smoothing Parameters in the Setup menu (section 3.2.2) to optimize smoothing for
the Fiber/Slit diameter that is used (for –USB2 platform AvaSpecs optimal smoothing is preset
and stored on board in the EEPROM).
4. Now turn on the light source. Usually some sort of spectrum may be seen on the screen, but it is
possible that too much or too little light reaches the spectrometer at the present data collection
settings. Too much light means that, over a certain wavelength range, the signal is saturated
shown as a straight line at the maximum counts and the appearance of the label “saturated” in
the statusbar of the spectrometer channel. This can usually be solved by a shorter integration
time. The integration time can be changed in the main window, in the white box below the
start/stop button. If AvaSoft is collecting data, the start/stop button shows a red „stop‟ and the
integration time box is gray, indicating that it cannot be changed (USB1). After clicking the
„stop‟ button the data acquisition stops and the integration time can be changed. The result of
the changed integration time can be viewed after clicking the green „start‟ button. Try to adjust
the integration time, such that the maximum count over the wavelength range is around 90% of
the full ADC scale (14750 counts for the 14bit ADC, 59000 counts for the 16bit ADC). When at
minimum integration the signal is still too high, an attenuator, a neutral density filter or fibers
with a smaller diameter may be used. When not enough light reaches the spectrometer, likewise
a longer integration time should be entered.
5. When a good spectrum is displayed, turn off the light source.
6.
Now save the Dark data. This is be done by File-Save-Dark from the menu or by clicking the
black square on the left top of the screen with the mouse. Always use Save Dark after the
integration time has been changed.
7.
Turn on the light source again. Save the present spectrum as a reference by choosing File Save-
Reference from the menu or by clicking at the white square (next to the black one). Always use
Save Reference after the integration time has been changed. Now the
Transmittance/reflectance (T/R button) or Absorbance (A button) spectra can be obtained
online. To have a better look at the amplitude versus wavelength, the cursor button can be
clicked. A vertical line is displayed in the graph. If the mouse cursor is placed nearby this line,
the shape of the mouse cursor changes from an arrow to a „drag‟ shape. If this shape is
displayed, the left mouse button can be used to drag (keep left mouse button down) the line
with the mouse towards a new position. Moving this line shows the corresponding values of
wavelength and amplitude in the main screen. By clicking the red stop button, the data
acquisition is stopped and the last acquired spectrum is shown in static mode. The data
acquisition can be started again by clicking the same button, which now shows a green „Start‟.
8.
To save the spectrum (in the mode chosen before), choose File-Save-Experiment from the menu,
or click the Save Experiment button from the button bar.
9.
To improve the Signal/Noise ratio, a number of spectra may be averaged. To do this, the value
in the white average box in the main window (next to integration time) can be increased. The
value can only be changed in static mode. When AvaSoft is acquiring data, the average box
becomes gray (USB1 platform).
