Guralp Systems CMG-DM24 - Manual (Page 42)

CMG-DM24
Pre-trigger and post-trigger recording
In order to capture all of a seismic event, it is often useful to be able to
record data immediately preceding the trigger. Güralp digitizers have
an internal buffer of some seconds which allows this data to be added
to the triggered stream. Pre-trigger data is particularly useful for
emergent-type signals, where the system does not trigger until one
phase after the first arrival. In addition, to ensure that the coda of each
event is included, some seconds of data are recorded after the system
detriggers.
The two boxes at bottom right of the Triggering pane allow the user to
set the pre-trigger and post-trigger data intervals, in seconds. These
values determine the minimum length of time during which data will
be saved before the trigger condition occurs, and after it has lapsed.
Regardless of the intervals chosen, the data in the triggered streams
will begin on a whole second boundary.
Mux Channels
Güralp digitizers provide a range of slow-rate auxiliary channels for
reporting the system's state of health and other diagnostic information,
known as multiplexed (“Mux”) channels. The number of Mux
channels depends on the model and configuration of your digitizer.
Generally, three channels are used to report the sensor mass position,
and another measures the internal temperature of the digitizer. In
addition to these, up to 12 Mux channels may be supplied for the
user's own purposes. Some digitizers have a separate AUXILIARY port
which can be used to access these channels.
The collection and transmission of Mux channels is controlled using
the Mux Channels pane:
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