User manual

Connections
Version 1.5 28
7.8 Trigger
The trigger mode is very useful for surveillance and machine vision
applications.
For example, a light barrier can simultaneously send out a trigger
pulse to the SCB-12 and to a harddisc recorder when somebody
enters a room. Most normal recording devices can not start record-
ing within a fraction of a second. If such a camera outputs a live
image either a later image which does not show the exact situation
is recorded or the recorder saves a stream of images and, there-
fore, requires a large amount of data space.
7.8.1 NORMAL MODE (Free Running)
In normal mode (Trigger is de-activated by default) the camera
generates live images with a frame rate of 30 fps. The duration of
exposure can be changed in the on-screen menu with the shutter
setting. The sampling time is controlled by the camera electronics
and can not be changed.
7.8.2 TRIGGER MODE
The SCB-12 offers a trigger input to determine the moment of im-
age readout.
When the TRIGGER-function is activated, the sampling time is
controlled by receiving trigger-pulses (pulse with 3.3 to 40Vss; pos-
itive or negative edge, selectable in the on-screen menu - see page
29ff).
The image is processed 1/30s after the camera receives the trigger
pulse.
The exposure time is variable and determined by the shutter time.
However, the end of exposure is always 1/30s after the trigger
pulse. The start of exposure is also determined by the shutter time
(Shutter is adjustable in the on-screen menu).
The maximum trigger frequency is 15Hz (2x 1/30s). This will result
in a maximum frame rate of 15fps.
When switching on the Trigger mode in the on-screen menu, the
SCB-12 freezes the current image. The next image will be pro-
cessed when the SCB-12 receives a trigger pulse.
When the time between the trigger pulses is too short, the mes-
sage "Trigger Overrun" will appear on the screen. Decrease the
trigger pulse frequency to rectify this.
7.8.3 Example with positive trigger edge