Guralp Systems CMG-3ESPCD - Manual (Page 44)

CMG-3ESPCD Digital Broadband Seismometer Using Scream!
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Z4, N4, E4 correspond to input channels Z, N, and E, output through
Tap 2. A six-channel digitiser connected to two triaxial instruments
will use Z0, N0, E0, Z1, N1, E1 for tap 0; Z2, N2, E2, Z3, N3, E3 for
tap 1; Z4, N4, E4, Z5, N5, E5 for tap 2; and Z6, N6, E6, Z7, N7, E7 for
tap 3. The digitiser in the example has only one triaxial instrument
connected to it, so Z/N/E1, 3, 5 and 7 are unused.
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00 is the digitiser status stream (notice: zero sample rate).
Other streams you may see include •
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M8, M9, MA: slow-rate Mux channels reporting the sensor mass
positions for the Z, N, and E components (“Mux Channels” in Section
4.1).
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ME: another Mux channel, normally used for reporting the digitiser's
internal temperature.
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CD, BP, IB: digitiser streams for specialised use.
5.1.3 Triggering
In its standard configuration, the digitiser outputs continuous data at a
sample rate you specify. In addition to this, Güralp digitisers can run a
triggering algorithm on the data they acquire. 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 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! also allows you to configure 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:
MAN-C3E-0002 44 Issue B - November 2013