Guralp Systems CMG-DM24 - Manual (Page 33)

Operator's guide
Each configurable tap can be set to a different decimation factor by
choosing values from the drop-down menus on the left. Decimation
factors of 2, 4, 5, 8, and 10 are available. The numbers visible in the
drop-down menu of each tap are the data rates that each of the
possible decimation factors will provide, given the settings of the taps
above it. Only integer (Hz) data rates are allowed: thus, for example, if
one tap emits data at 25 Hz, the only possible further decimation factor
is 5.
To the right of each decimation factor menu is a grid of check-boxes.
These boxes mark which streams of data to generate at each sample
rate. The screen-shot above shows a possible configuration for a
triaxial instrument. Every channel of the digitizer may be output at
any tap; In the example above, all three axes are being output at Tap 2
(20Hz). The DM24 MkIII has a fourth channel for external input and
calibration, which can also be output at any tap.
If you want to change the names used for the channels, click in the
white box containing a Z in the above picture, and type a letter or
number. It will name the channels with a sequence of letters or
numbers beginning with the one you choose (e.g. A, B, C; 2, 3, 4; 9, A,
B), unless you type Z in which case they will revert to Z, N, and E.
Each combination of channel and tap has two check-boxes:
•
Checking the upper check-box of each pair makes that tap
output data continuously for that component;
•
Checking the lower check-box makes that tap output data only
when a trigger is active.
In the example above, the digitizer will output data continuously for
all three channels at Tap 2, but never for any other taps. If you do not
need all the streams to output at all rates, you should leave boxes
unchecked to save communications capacity.
You cannot check both continuous and triggered output for the same
channel and tap.
When you enable a triggered stream, the digitizer will output data in
that stream only when a particular set of trigger criteria are met. To
remind you that the streams are not continuous, the window shows
the data streams (lines) passing through a “switch”.
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