Guralp Systems CMG-DM24 - Manual (Page 25)

Operator’s Guide DM-24 Digitiser
Issue G January 2003 23
A tick in a box will give an output for the corresponding channel (column) at
the corresponding sample rate (row). For each sample rate there are two
possible rows to tick. The upper row for each sample rate will give a
continuous output at that sample rate; the lower row, shown diagrammatically
as passing through a switch, will only output data when its trigger criteria are
met (see below).
The Stream IDs displayed in the main Available Streams window has six-
character ID’s. The first four characters identify the digitiser, the last two
characters identify the stream from the digitiser. The first of these two
characters identify the channel, the second defines the ‘tap’, or digitiser output
( see Data Transmission Protocol & Data Block Structure later).
For example; for the Output Control configuration shown above, at the
beginning of this sub-section, there will be three data streams, Z, N and E,
outputing data at 100sps, 20sps and 2sps. This is shown below, where the
digitiser ‘1123’ has the following streams:-
•
Z2, N2, E2 are input channels Z, N, E output through the second tap ‘2’;
•
Z4, N4, E4 are input channels Z, N, E output through the third tap ‘4’,
•
Z6, N6, E6 are input channels Z, N, E output through the fourth tap ‘6’,
•
00 is the digitiser status stream (notice no sample rate),
•
M8, M9, MA are sensor mass positions for Z, N, E channels
•
MB, ME, MF are three of the optional eight 16bit channels available
Triggered output stream selection: For each tap there are two rows of boxes where
the user can tick either triggered or continuous data outputs. The digitiser
applies a simple short term average (STA) - long term average (LTA)
algorithm to a selected stream or set of streams to determine whether the
trigger condition is met. These streams may be bandpass filtered before
evaluation using standard bandpass parameters. The data transmitted due to the
trigger may be from different streams than those used to determine the trigger.
System
Identifier
Serial
Number
Channel & tap number