User`s guide

TRIGGERING
SDK SECTION 5
Page 51
External
In External Trigger Mode once an acquisition has been started via the
StartAcquisition function the
camera is placed into a special dumping version of the ‘Keep Clean’ mode, which ensures that the CCD is
not saturated before the external trigger occurs. Once the External Trigger is received the Keep Clean
sequence is stopped and the acquisition is initiated.
The figure below illustrates the timing sequence for this mode of operation:
The external trigger can be fed in a number of ways:
• EXT TRIG socket of the I/O Box (available separately, model #IO160)
• Pin 13 of the Auxiliary Connector on the Andor PCI Card
• The head in the case of iDus / iXon.
External Trigger mode is suited to data acquisitions involving a ‘pulsed source’ (e.g. a laser) where the
source does NOT allow a trigger pulse to be sent to it but can generate one. It is possible to increase the
frame rate when in external trigger mode by enabling the Fast External Trigger option, see
SetFastExtTrigger.
When this option is enabled the system will not wait for a Keep Clean cycle to be completed before allowing
an external trigger to initiate an acquisition. This may cause the background to change from one scan to
another.