Using the DM24
4.5.1 Downloading over FireWire
To download data over FireWire, plug the disk in and issue the command
DISKMENU
from the digitiser's console. The digitiser will reply with a list of download options.
If you have not used the disk before, you will need to reset it. Resetting the disk
prepares it for the DM24 to use and sets up the DFD filing system (see below). Press
then
ENTER
to reset the disk. When the DM24 is ready, it will return to the menu.
You can also use GCFXtract or Scream! to prepare a FireWire disk.
To download all the new data held by the DM24, press
then
ENTER
, or wait for 10
seconds. The DM24 will transfer any data it has recorded since the last download
and then mark these as transferred.
You can also download selections of data (including the entire contents of the data
store, if desired) with the
DISKMENU
command. See Section 6.11 on page 82 for more
information.
The DM24 checks for a FireWire disk when it boots up. If there are enough new data
waiting to be transferred (by default 128 Mb), the DM24 will automatically transfer
them onto the disk. The digitiser then updates its internal pointers to mark these
data as already downloaded.
This feature is particularly useful for autonomous installations: after the digitiser
has been retrieved from a field experiment, simply powering it up with a prepared
disk attached will make it transfer all the data it has recorded during the
experiment.
While the FireWire interface is active, it will consume about 200 mA of current (from
a 12 Volt supply). If you interrupt a transfer whilst it is in progress, the digitiser will
re-boot and will not mark data as downloaded. Because of this, the next time you
transfer data, some will be duplicated. You will not, however, lose any data.
4.5.2 Reading DM24 disks
When the DM24 saves data onto a FireWire disk, it uses a special format called
DFD
.
You can read these data into a PC using Scream! or the GCFXtract utility, which is
freely available from the Güralp Systems Web site. Linux and Solaris command line
utilities are also available for reading data from a DFD disk.
The DFD format is
not
the same as that used by the Güralp Systems EAM data
acquisition module, which uses a FAT32-compatible journaling file system.
Güralp Systems can provide fully-tested, formatted disks with FireWire and USB
connectors. Alternatively, a third-party FireWire disk may be used (although
compatibility is not guaranteed).
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Issue U - December, 2021