Guralp Systems CMG-DM24S12AMS - Manual (Page 20)

CMG-DM24S12AMS Operator's guide
Triggering
In its standard configuration, the digitiser modules inside the
DM24S12AMS output continuous data at a sample rate you specify. In
addition to this, the digitiser can run a triggering algorithm on the data
it acquires. This allows you to record data continuously at a relatively
low sample rate, but record at a much higher sample rate during short
periods when the trigger is active. The parameters controlling the
triggering algorithm, and controlling the data output once the system is
triggered, are all selectable by the user, permitting maximum flexibility
of operation and the most efficient use of available storage space.
The digitiser modules inside the DM24S12AMS can be set up for
triggered output, that is, to output certain data streams only when a
particular trigger criterion is met. The trigger criterion can be tested with
data from the same or some other stream. For example, you could use a
later tap (with a lower sample rate) as a trigger for output from an
earlier, more detailed tap. Scream! 4 also allows each digitiser to receive
triggers from other digitisers.
To create a new stream with a trigger, open Scream!'s Digitiser
configuration window for the relevant digitiser, and click on the Output
control tab. In the Output control pane, a tap which gives rise to a
triggered stream has a tick in the lower row of its grid of check-boxes.
You cannot configure the trigger criteria until you have selected at least
one stream to be affected by the trigger.
Once you have decided which streams should be output when the
trigger is activated, you will be able to click on the Triggering button to
describe the trigger condition. Alternatively, click on the Triggering tab
at the top of the window. Either action will open the Triggering pane:
20 Issue B