Ocean Optics Apex Install - Manual (Page 18)

A: Calibrating the Wavelength of the Apex
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Calibrating the Spectrometer
Preparing for Calibration
To recalibrate the wavelength of your spectrometer, you need the following components:
• A light source capable of producing spectral lines
Note
Ocean Optics’ HG-1 Mercury-Argon lamp is ideal for recalibration for wavelengths up to
922 nm. For wavelengths above 922 nm, we recommend the XE-1 Xenon Light Source.
If you do not have an HG-1, you need a light source that produces several (at least 4-6)
spectral lines in the wavelength region of your spectrometer.
• An Apex spectrometer
• An optical fiber (for spectrometers without a built-in slit, a 50-
µ m fiber works best)
• A spreadsheet program (Excel or Quattro Pro, for example) or a calculator that performs third-
order linear regressions
Note
If you are using Microsoft Excel, choose Tools | Add-Ins and check AnalysisToolPak
and AnalysisTookPak-VBA.
Calibrating the Wavelength of the Spectrometer
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Procedure
Perform the steps below to calibrate the wavelength of the spectrometer:
1. Place the spectrometer operating software into Scope mode and take a spectrum of your light
source. Adjust the integration time (or the A/D conversion frequency) until there are several
peaks on the screen that are not off-scale.
2. Move the cursor to one of the peaks and position the cursor so that it is at the point of maximum
intensity.
3. Record the pixel number that is displayed in the status bar or legend (located beneath the graph).
Repeat this step for all of the peaks in your spectrum.
4. Use the spreadsheet program or calculator to create a table like the one shown in the following
figure. In the first column, place the exact or true wavelength of the spectral lines that you used.
In the second column of this worksheet, place the observed pixel number. In the third column,
calculate the pixel number squared, and in the fourth column, calculate the pixel number cubed.