Ocean Optics Red Tide Guide User Manual
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170-00000-RT-02-1108
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REFERENCE READING
A reference reading is a
spectrum that is stored for
mathematical comparison with sample read-
ings to be taken.
Reference readings are normally taken with the ISS-VIS
lamp with cuvette holder attachment as shown, using an
empty cuvette or one containing the solvent in use.
Reference readings can be taken using the fiber optic
probe. However the probe and source must be clamped in
position for this to work. The slightest movement in the
probe will change the readings.
Switch on the lamp by checking the Strobe/Lamp Enable
box.
Adjust the integration time to give a refer-
ence
reading that has a maximum count of about 3500.
Click on the Store Reference Spectrum icon
(See Fig.4).
When both dark and reference readings have been taken,
all the experiment modes go live. See Fig 6.
Note:
Reference and dark readings must be taken with the same
integration time. All samples must stick to this integration
time or the results will be meaningless.
Fig. 5
TRANSMISSION
Transmission is the sample intensity as a
percentage of the reference intensity.
When you select Transmission mode, the
y-axis units change to percentage.
Transmi
ssion % =
ABSORBANCE
Absorbance is the inverse of transmission, but on a log
scale. When you select Absorbance mode the y-axis
changes to a log scale of Absorbance number.
Absorbance = - log
10
Where:
S
λ
=
Sample intensity at wavelength λ
D
λ
=
Dark intensity at wavelength λ
R
λ
=
Reference intensity at wavelength λ
Reference and dark spectra must be stored before col-
lecting experiment data. If you pass the cursor over the
No-preprocessor
line in either the Data Sources or Data
Views pane, a tool tip box informs you whether reference
and/or dark spectra have been stored.
For Reflectance and Irradiance, please refer to the main
SpectraSuite manual. This is in the Help menu.
T
S
λ
- D
λ
R
λ
- D
λ
)
(
A
S
λ
- D
λ
R
λ
- D
λ
)
(
x 100
Fig. 6
A - Absorbance
T - Transmission
R - Reflectance
(Advanced users)
I - Irradiance
(Advanced users)
3