Ocean Optics External Triggering Options - Manual (Page 4)

External Triggering Options Instructions
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Level Triggering and Edge Triggering
In External Triggering, there are two modes of triggering available. The trigger mode in use determines
the kind of triggering that the system will use.
Level Triggering
Level triggering mode is only available when using External Software Triggering mode. In this mode, the
software monitors the A/D converter for an increase in the voltage level applied to the trigger pin. When
the appropriate increase in voltage is received (5 volts), the software instructs the spectrometer to acquire
spectra.
In this mode, the A/D converter will acquire data in intervals based on the integration time set in the
software. Thus, if a trigger occurs in the middle of an integration period, the software will retrieve the
spectra obtained for that entire integration period (before AND after the trigger event). Similarly, if a
trigger occurs immediately prior to the end of an integration period, the software will still retrieve the
spectra obtained during that integration period.
For example, if the integration time is 50 ms and the trigger event occurs 48 ms into the integration cycle,
the 2 ms following the trigger will be acquired, and the 48 ms prior to and including the trigger will be
acquired.
Edge Triggering
Edge triggering mode is available when using External Hardware and External Synchronization
Triggering modes. In both of these modes, the spectrometer monitors the trigger input pin for rapid rise
in the voltage (which may or may not reach the 5 volt plateau) applied to the trigger pin. When this
voltage rise is received and the spectrometer “sees” the voltage peak caused by the increase, the
spectrometer acquires spectra and transmits the spectra to the software.
In External Hardware Triggering mode, the spectrometer begins an acquisition upon receiving trigger and
acquires for one integration cycle. In External Synchronization Triggering mode, however, data
acquisition continues until the next rise in voltage is “seen” by the spectrometer.