Thermonicolet Omnic Software User's Guide 6.1 (PDF) - Charles E ...

When deciding whether to use this feature, keep in mind that a tradeoff exists: The
benefit, removing gross atmospheric signals from the spectral data, is offset to
some extent by the introduction of minor artifacts.
These artifacts are due to a combination of factors. One is the natural bias from
statistics; when absorptions are caused by unknown components, this is
unavoidable. The other factor is the fact that there may be atmospheric signal that
is not described in the set of standards used to develop the quantitative model.
You can improve this by adding your own standards. (See the explanation above.)
Note
You can also use the water and carbon dioxide corrections available through
Corrections on the Collect tab or Other Corrections in the Process menu to correct
spectra for absorptions due to water vapor and carbon dioxide. However, we
recommend using Automatic Atmospheric Suppression instead, unless you find that
the humidity in your facility is too high for it to work effectively. ▲
Checking spectrometer
performance at the
start of data collection
Turn on Preview Data Collection if you want to collect and view (but not save)
preliminary data before the start of a sample or background data collection. This
lets you verify that your experimental conditions are correct before collecting the
spectrum.
If you choose Collect Sample or Collect Background from the Collect menu when
the parameter is on, the system continuously collects and displays data in the
specified final format until you click the Start Collection button.
Entering an
experiment description
Type a description of the experiment in the Experiment Description box. When
you save the experiment and open or select it later, the description will appear in
the box, serving as a reminder of the experiment’s purpose or as a record of other
useful information.
File handling
The options in the File Handling box let you save collected spectra automatically.
Turn on Save Automatically to save spectra immediately after collection. (Final
Format determines the Y-axis unit used.) The files are named with a four-character
base name plus a sequence number with up to four digits, followed by an extension.
Type a name in the Base Name box or select a base name from the drop-down list
box. Use a descriptive base name for each group of samples so you can find them
easily later. After you specify a base name and then perform another operation, the
path that will be used when the spectra are saved appears below the Base Name box.
The extension and sequence number are assigned by the software, with the
extension .SPA used for sample and background spectra. The sequence number is
increased by one each time you collect a spectrum. For example, if the base name
is POLY, the first sample will be named POLY0001.SPA, the second
POLY0002.SPA and so on. If you use a previously used base name, the sequence
numbers for new files will begin where the previous numbers left off.
The spectra are saved in the directory indicated by the path below the Base Name
box. You can change this path by using the File options (available through Options
in the Edit menu; see “Specifying directories” in the “Edit” chapter for details).
118 Thermo Nicolet