Guralp Systems CMG-CD24 - Manual (Page 33)

Operator's Guide
The spectral amplitudes for the various frequency responses available
are shown in the figures below.
3.1.3.2 Level
Using the Level triggering method, a trigger is generated whenever one
of the checked components reaches a certain level above the baseline.
Note: All unfiltered seismic signals will have some degree of
offset - i.e. the average value will rarely be zero. It is strongly
recommended that a high-pass filter is used to prevent this
offset from affecting the level triggering algorithm but please be
aware that the high-pass filters also affect the main outputs.
To configure Level Triggering:
1. On the Output Control tab, set the Highpass filter to 100s, 300s or
1000s to alleviate any offset problems. Note that this filter is
applied directly to the continuous data streams and, so, will also
affect the main outputs.
2. On the Triggering tab, select the tap to be triggered from the Data
source drop-down menu and the channel(s) to be considered from
the Channel column of the table.
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