Instruction manual

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2 Acquisition 16
a small piece of data prior to the trigger. To enable pretriggering, check the box next to the label
Pretrigger (in the Start Mode box on the Channel page of the Preferences dialog window).
Enter the amount of pretrigger time needed in the edit box to the right of the Pretrigger label.
Stopping Once recording begins, the DataTrax2 programs offers two different ways to halt the recording:
User or Timed
.
Figure 2-3: The Stop dialog boxes.
User User is the default Stop value for DataTrax2 and can be reset from the Stop Mode box on the
Channel page in the Preferences dialog window. In User mode, the Stop button in the upper
right hand corner of the DataTrax2 Main window will stop the recording when clicked. The
Record button changes to the Stop button after the Record button is clicked to begin the
recording. The Stop button remains visible until it is clicked. Clicking the Stop button will
change it back to Record.Timed
When Timed is selected as the stop mode, the DataTrax2 software will stop recording
automatically after a predetermined time (in seconds), which is entered into the edit box.
Pausing Display It is sometimes desirable to pause the scrolling display of data while at the same time
continuing to record data. In DataTrax2, this is accomplished by clicking the Pause Display
button in the lower left hand corner of the Main window.
Scope Mode
When to Use
the Scope
Mode
The first devices used to record data were electromechanical. These devices used a stylus or
very fine pen that was moved by a sensitive motor. The frequency response of these machines
was very low; the fastest events that they could record were on the order of tenths of a second.
As science progressed, it became obvious that there were faster things in nature than pen
recorders could visualize. The oscilloscope or “scope” is able to take a fast, brief snapshot of an
event, but the continuous chart-like recording is sacrificed. An oscilloscope capturing a fast
moving electrical signal, like an action potential, is analogous to high speed, stop motion
photography capturing the movement of a hummingbird’s wing.
To effectively use the Scope mode in the DataTrax2 program, the length of the snapshot
(display time) and the sampling rate need to be set to accurately visualize the event. Events that
are best captured using the Scope mode are brief and repetitive. Action potentials and most
neurophysiological signals are good examples of signals that are best recorded in Scope mode.
In addition to being able to capture a very brief event in time, a proper trigger is needed to
begin the recording of the event at the moment it takes place. Using the example of stop motion
photography, if the high speed camera snapped the picture too soon or too late, the picture may