7: Calibration
60 225-00000-000-11-201604
C
3
= the third coefficient (nm/pixel
3
)
You will be calculating the value for
I
and the three
C
s.
Calibrating the Spectrometer Wavelength
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. 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.
A Flame spectrometer
An optical fiber (for spectrometers without a built-in slit, a 50-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
► Procedure
Perform the steps below to calibrate the wavelength of the spectrometer:
1. Place the spectrometer operating software into Quick View (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.
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