Ocean Optics OOIIrrad-C - Manual (Page 50)

5: Calibration
Absolute irradiance measurements can be achieved in two ways:
• Ocean Optics can calibrate the spectrometer for you and send you the resulting calibration file, or
• You can calibrate the spectrometer yourself using a light source (calibration lamp) with known
spectral output (microwatts per square centimeter per nanometer).
Absolute Irradiance Calibration Using a Provided Cal File
► Procedure
To take an absolute irradiance measurement using the calibration file provided by Ocean Optics,
1. Select
Calibrate | Absolute Irradiance from the menu bar. The Irradiance Calibration
screen appears.
2. Select Spectrometer | Active Spectrometer Calibration File from the menu bar on the
Irradiance Calibration screen.
3. Navigate to the spectrometer file that you want to use. Open the file.
4. Select File | Close to return to the main window.
5. Click the Store Dark button to take a dark scan at your current integration time.
6. Change the
Spectral Graph Mode to uW/cm^2/nm or uW/nm.
7. Watch the Scope Mode graph (black graph on bottom right of screen) to ensure that you
are not saturating the detector when taking measurements.
When you close then reopen the software, OOIIrrad-C restores and continues using the last calibration file
that you used.
Absolute Irradiance Calibration Using a Calibration Lamp
You have the option of calibrating the spectrometer yourself using a light source (calibration lamp) with
known spectral output (microwatts per square centimeter per nanometer). The known spectral output
specifies the power at a certain distance from the lamp. After placing the sensing area (fiber tip, CC-3
cosine corrector, etc.) at this specified distance from the lamp, the OOIIrrad-C application creates a
conversion factor for each pixel. This conversion factor results from the lamp’s known output intensity
and the actual spectrometer reading from detected light (counts). These calibration results are specific to
the optical configuration (from the spectrometer to the sensing area) used during calibration. Therefore, it
is necessary for you to calibrate our spectrometer according to your unique configuration. Should your
configuration change (for example, if a different slit is installed, or a different fiber is used to collect
light), a new calibration is needed.
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