Ocean Optics OOIBase16 - Manual (Page 6)

4
Print
This command displays a dialog box allowing you to print the current spectrum. The graph title, grid and
cursor are all printed if they are displayed on the screen.
Exit
This command exits OOIBase.
View Menu Functions
Scope Mode
This command switches the current window into Scope Mode. The signal graphed in Scope Mode is the
raw voltage coming out of the A/D converter. Once you open OOIBase and it begins to acquire data, you
see the raw voltage from the detector expressed in A/D counts. This spectral view mode is unique to Ocean
Optics and allows the user the ability to have complete control of signal processing. Be careful when using
this mode, as it represents a combination of several factors: the intensity of the light source, the reflectivity
of the grating and the mirrors in the spectrometer, the transmission of the fibers, the response of the
detector, and the spectral characteristics of the sample. Scope Mode should only be used to select signal
acquisition functions.
Absorbance Mode
This command switches the current window into Absorbance Mode. Before this can occur, both the dark
and reference spectra must be stored while in Scope Mode. (See
Doing an Experiment on page 15 for
details.) The absorbance of a solution is related to the concentration of species within it. The relationship,
known as Beer’s Law, is:
A λ =
ε
λ c
l
A = absorbance at wavelength λ ,
ε
= extinction coefficient of the absorbing species at wavelength λ ,
c = the concentration of the absorbing species, and
l
= the pathlength of the absorption.
This relationship is used to determine the concentration of a species in solution. Absorbance is calculated
by the following equation. When this equation is evaluated for each pixel of the detector, the absorbance
spectrum is produced.
S λ - D λ
A λ = - log
10
(
R λ - D λ
)
S λ = sample intensity of each wavelength, D λ = dark intensity of each wavelength,
R λ = reference intensity of each wavelength, λ = each wavelength
Transmission Mode
This command switches the current window into Transmission Mode. Before this can occur, both the dark
and reference spectra must be made and stored while in Scope Mode. (See
Doing an Experiment on page
15 for details.) The transmission of a sample is calculated by the following equation:
S λ - D λ
%T λ =
R λ - D λ
x 100%
S λ = sample intensity of each wavelength, D λ = dark intensity of each wavelength,
R λ = reference intensity of each wavelength, λ = each wavelength