56 PI-SCX System Manual Version 2.E
56
Cleans modes, opens the shutter as soon as the ST-133 is ready to receive an External
Sync pulse. This is required if the time between the External Sync pulse and the event is
less than a few milliseconds, the time it takes the shutter to open.
The shutter timing is shown in the timing diagrams that follow. Except for Free Run,
where the modes of shutter operation are identical, both Normal and PreOpen lines are
shown in the timing diagrams and flowchart.
The timing diagrams are labeled indicating the exposure time (t
exp
), shutter compensation
time (t
c
), and readout time (t
R
). Note that if there is no shutter selected in the software, the
shutter compensation time (the time required to close a mechanical shutter) will be
approximately 0 ms.
Free Run
In the Free Run mode the controller does not
synchronize with the experiment in any way. The
shutter opens as soon as the previous readout is
complete, and remains open for the exposure time, t
exp
.
Any External Sync signals are ignored. This mode is
useful for experiments with a constant light source.
Other experiments that can utilize this mode are high
repetition studies, where the number of shots that occur
during a single shutter cycle is so large that it appears to
be continuous illumination.
Other experimental equipment can be synchronized to
the ST-133 controller by using the output signal
(software-selectable SHUTTER or NOT SCAN on the
Hardware Setup|Controller Camera tab) from the
connector. Shutter operation and the NOT
SCAN output signal are shown in Figure 23.
Figure 22. Free Run Timing Chart,
part of the chart in Figure 28
Figure 23. Free Run Timing Diagram
External Sync
In this mode all exposures are synchronized to an external source via signal input to the
Ext Sync BNC on the back of the ST-133. To ensure synchronization, the trigger edge
(negative- or positive-going) of the Ext Sync signal must be identified in the application
software (in WinView and WinSpec, this is done on the Experiment Setup|Timing
tab). As shown in the flowchart, Figure 24, External Sync mode can be used in
combination with Normal or PreOpen Shutter operation. In Normal Shutter mode, the
controller waits for an External Sync pulse and then opens the shutter for the