10
Display Functions
Several functions are accessed not through the menu but through buttons and task bars directly on the display
screen, on the top and to the right of the graph area. (The resolution of your computer's monitor must be 800 x
600 or better to view OOIChem software.) From the display screen, you can choose a mode of operation,
configure the cursor, configure the graph, enter acquisition parameters, choose a mode to acquire data, take
reference, dark, and sample scans of your sample, and scale the graph.
Spectrometer Channel Selection
The Spectrometer Channel area allows you to animate the window for a
specific spectrometer channel. Though the standard CHEM2000 and
CHEM200-UV-VIS are single spectrometer channel systems, you can
purchase additional channels at any time. For now, select
Master
.
Mode of Operation
Scope
The signal graphed in Scope Mode is the raw voltage coming out of the A/D converter. Once you open
OOIChem 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. It allows you to control signal processing
functions before taking absorbance, transmission, and relative irradiance measurements. 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 primarily be used when selecting signal
acquisition parameters such as integration period, averaging and
boxcar smoothing; and when taking dark and reference scans.
Absorbance
Selecting this mode switches the spectral window into Absorbance Mode. Before this can occur, both a
dark and reference scan must be stored in Scope Mode. (See the
Experiment Tutorial
beginning on
page 27.) 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
)
where
S
is the sample intensity at wavelength
λ
,
D
is the dark intensity at wavelength
λ
,
R
is the
reference intensity at wavelength
λ
.
Transmission
Selecting this mode switches the spectral window into Transmission Mode. This is also the spectral
processing mode used for Reflection spectroscopy, as the math necessary to compute reflection is
identical to transmission. Before this can occur, both a dark and reference scan must be stored in Scope
Mode. (See the
Experiment Tutorial
beginning on page 27.) The transmission of a solution is
calculated by the following equation:
S
λ
-
D
λ
%T
λ
=
R
λ
-
D
λ
x 100%
where
S
is the sample intensity at wavelength
λ
,
D
is the dark intensity at wavelength
λ
,
R
is the
reference intensity at wavelength
λ
.
