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Triggering
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Synchronized Triggering to an External Event
Acquisition of image or spectral data can be initiated and synchronized to an external
system event by using the trigger input capability of the Synapse’s TTL Input. This
TTL input line uses edge triggering, which is user programmable via software control
to recognize positive or negative edge triggered events. This external triggering
capability can be used to activate the start of each experiment, as well as, to initiate
each acquisition of an experiment involving multi-acquisitions.
It should be noted that once the detector has recognized a valid external trigger pulse,
any and all subsequent activity on this external input will be ignored until the
integration period and CCD readout time have completed for the acquisition at hand.
For experiments involving multiple acquisitions, the allowable repetition rate (t rep
rate) associated with this external triggering function is governed by the sum of the
CCD expose time (t expose) and subsequent data processing readout time (t readout)
as follows:
t
rep rate
≥
t
expose
+
t
readout
Figure 7, on the following page, illustrates the relative timing associated with an
external trigger input waveform and the subsequent expose (i.e. shutter) and readout
timing information available via the TTL Output. Figure 7 depicts an externally
triggered single acquisition experiment using positive edge triggering for the Trigger
Input signal and active high logic levels (5 V) all output signals shown.