74
Apr-09
Avantes
www.avantes.com
Where
B
is the computed component of the spectral distribution of the blackbody radiant emittance
(at user selected temperature in degrees Kelvin), divided by the current reference data at
wavelength
How to take relative irradiance measurements with AvaSoft
1.
Start the AvaSoft software, and click the Start button in the main window.
2.
Connect a fiber to the Spectrometer input port.
3.
Adjust the Smoothing Parameters in the Setup menu to optimize smoothing for the Fiber/Slit
diameter that is used.
4.
Set up the experiment such that the other end of the fiber points at the sample of light to be
determined (use a fixture for the best results). 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 overloaded shown as a straight line at any arbitrary height, even near zero. 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. 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, fibers with a smaller diameter can 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 done by File-Save Dark from the menu or by clicking the black
square on the left top of the screen with the mouse.
7.
Turn on the
reference light source of known color temperature
(2850K for AvaLight-HAL
with default jumper setting) and set up the fiber end that is not connected to the
spectrometer, so that a good spectrum is displayed on the screen. Note that the integration
time or fiber type may not be changed while measuring the reference data. If there is too
much light, adjust the focusing of the light source, so less light is coupled into the fiber. As
long as only light from the reference light source and no ambient light is coupled into the
fiber, this will not influence the spectral distribution, only its height. Try to set up the fiber
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).
8.
Save the Reference data. This is done by File-Save Reference from the menu or by clicking the
white square on the left top of the screen with the mouse.
9.
Note that the whole operation of saving a reference file does not need to be carried out each
time a new experiment is started. The reference data are saved in a file called ref*.dat and
can be loaded next time by choosing the option File-Load Reference. After saving or loading
reference and dark the irradiance mode can be chosen by clicking the „I‟ button or by the
menu option View-Irradiance mode. First a message box appears in which the value of the
color temperature in Kelvin of the light source that has been used as a reference can be
entered. If light from the reference light source is viewed, the Planck-curve for the color
temperature of the reference light source is displayed, as shown in the figure on the next
page. The maximum of the reference Planck-curve has been set to 100.
dark
sample
B
S
*
