Guralp Systems CMG-DM24 User Manual
CMG-DM24
Mk3 Digitizer
Ope rato r's guide
Part No. MAN-D24-0004
Designed and manufactured by
Güralp Systems Limited
3 Midas House, Calleva Park
Aldermaston RG7 8EA
England
Proprietary Notice: The information in this manual is
proprietary to Güralp Systems Limited and may not be
copied or distributed outside the approved recipient's
organisation without the approval of Güralp Systems
Limited. Güralp Systems Limited shall not be liable for
technical or editorial errors or omissions made herein,
nor for incidental or consequential damages resulting
from the furnishing, performance, or usage of this
material.
Issue N 2009-10-05
CMG-DM24
Table of Contents
1 Introduction...............................................................................................................4
1.1 Features...............................................................................................................4
2 Installing the CMG-DM24.........................................................................................6
2.1 Power supplies....................................................................................................6
2.2 Connecting sensors.............................................................................................6
2.3 Connecting external hardware...........................................................................7
2.4 The DM24BH borehole digitizer........................................................................9
3 Using the DM24.......................................................................................................11
3.1 Taps...................................................................................................................11
3.2 Streams.............................................................................................................13
3.3 Transmission modes.........................................................................................15
3.4 Downloading stored data..................................................................................19
3.5 Reading DM24 disks.........................................................................................20
3.6 DM24 USB Host Operations.............................................................................24
4 Using Scream!..........................................................................................................29
4.1 Configuring digitizers.......................................................................................29
4.2 Controlling digitizers........................................................................................44
5 Command line interface..........................................................................................51
5.1 Introduction......................................................................................................51
5.2 Getting help......................................................................................................52
5.3 General configuration.......................................................................................53
5.4 Port configuration.............................................................................................57
5.5 Output configuration........................................................................................61
5.6 Triggering..........................................................................................................66
5.7 Calibration........................................................................................................71
5.8 Actions..............................................................................................................74
5.9 Data storage and transmission.........................................................................77
5.10 Downloading over the serial port...................................................................83
5.11 Downloading over FireWire...........................................................................87
6 Inside the DM24......................................................................................................89
6.1 State of health information..............................................................................89
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6.2 Updating firmware with Scream!.....................................................................94
6.3 Setting up external triggering ..........................................................................97
6.4 Technical details............................................................................................102
7 Güralp Compressed Format..................................................................................105
7.1 GCF blocks......................................................................................................105
7.2 Sending GCF streams over a network............................................................108
7.3 Sending GCF streams over a serial link.........................................................110
8 Connector pinouts.................................................................................................113
8.1 SENSOR A and B ports...................................................................................113
8.2 AUXILIARY port.............................................................................................114
8.3 GPS Port..........................................................................................................115
8.4 DATA IN port..................................................................................................116
8.5 FIREWIRE port................................................................................................117
8.6 USB port..........................................................................................................118
8.7 DATA OUT port..............................................................................................119
9 Digitizer specifications..........................................................................................120
10 Revision history...................................................................................................122
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CMG-DM24
1 Introduction
The Güralp CMG-DM24 multi-channel digitizer is a state-of-the-art
digital module for seismic data. It can be supplied in several different
formats:
A stand-alone DM24 (below) can be installed with existing or new
analogue sensors. Conversely, a modular digitizer is fixed to, and
becomes a physical part of, a Güralp seismometer. These can be
supplied with new instruments, or retrofitted to CMG-1T, 3T, 3ESP or
40T seismometers at the factory. A modular digitizer benefits from the
sensor's isolated, clean and stable environment and allows it to operate
at optimum noise levels and precision
The DM24 can also be supplied in borehole sonde form, with optional
strain relief accessories. All these units operate identically, although
the connector for the borehole unit is necessarily more compact.
A DM24 is especially powerful when operated in conjunction with a
Güralp data module such as the CMG-DCM or AM. All three types sensor, digitizer, and data module - can be customized to meet your
installation requirements.
1.1 Features
• A built-in Digital Signal Processor (DSP), which can provide
simultaneous multiple sample rate data streams at user
selectable rates. Up to 6 streams of data for each component are
available at sample rates from 1 to 1000 samples/s.
• A precision microprocessor-controlled time-base synchronizes
the Analogue-to-Digital Converters and the DSP, as well as
providing time-stamps for data blocks.
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• Time synchronization to an attached GPS receiver or from a
remote time source.
• An ARM microprocessor, which formats and buffers data in an
on-board 256k RAM ring buffer.
• Efficient data storage and transmission using the Güralp
Compressed Format (GCF).
• RS232 serial data output at user-selectable baud rates, with
automatic modem dial-out facility.
• Built-in microprocessor system configuration and sensor
control, including locking and unlocking, centring and
calibration.
• Low system power consumption.
• Flash EEPROM for program code and filter coefficients.
• High-impedance, low-noise, differential input pre-amplifier
modules with adjustable gain.
• Internal electronic thermometer provides temperature
measurements at an accuracy up to ± 0.33 °C, with a linearity of
± 0.5 °C.
• Optional Flash memory storage.
• Optional IEEE 1394 FireWire interface, allowing you to
download GCF data directly onto a compatible disk by simply
plugging the disk into the FireWire connector inside the casing,
and monitoring progress on the built-in LCD screen.
• Optional USB interface, enabling fast data transfer direct to a PC
or other recording device.
The DM24 can be connected to two Güralp analogue sensors, or up to
six conventional single-axis seismometers, through its SENSOR A and
SENSOR B connectors. (Single-sensor and integrated DM24 units have
only SENSOR A connectors). Signals from these sensors are digitized to
32-bit precision, initially at 2000 Hz. Data is output through the DATA
OUT serial port of the digitizer in the flexible GCF format, either to a
PC or a Güralp data module. Timing signals are gathered from a GPS
unit connected to the single GPS port.
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CMG-DM24
2 Installing the CMG-DM24
2.1 Power supplies
The DM24 accepts power from lines in its DATA OUT port. This is a
Güralp standard 10-pin combined serial/power interface, a cable for
which can be obtained from Güralp Systems. A standard 12V DC
power supply is recommended.
2.2 Connecting sensors
The DM24 is configured for use with Güralp Systems feedback
sensors, which can be connected directly to the SENSOR A and
SENSOR B ports. No further configuration of the sensor is necessary;
the input ports carry sensor power, four channels of differential
velocity, mass position and calibration signals. The AUXILIARY port
allows you to measure and digitize environmental parameters, e.g.
local temperature, pressure, or signals from other scientific
instruments.
In addition, two pins on the AUXILIARY port allow you to input signals
for a fourth, full-rate 24-bit data channel. This channel is digitized
continuously, but is interrupted when you calibrate the instrument, so
that the DM24 can return the calibration signal on a stream with a
different name. When calibration is over, the fourth channel returns to
digitizing the external source.
If you prefer, you can attach any seismometer with balanced
differential output to the signal inputs of the DM24. You will need to
make up a cable to connect the relevant pins of the SENSOR A or B
port to your instrument(s). See Section 8.1, page 113, for details of the
connector used.
If you have only one sensor, you should attach it to the SENSOR A
port, since only this port can be used to send control signals to it (e.g.
mass locking and unlocking). The SENSOR B port can therefore only
be used for sensors which do not require remote control signals, such
as Güralp accelerometers or the CMG-6 series of medium noise
instruments. The 4-channel model of the DM24 does not have a
SENSOR B port.
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2.3 Connecting external hardware
On a stand-alone DM24, the digital ports are located on the opposite
side to the analogue ports:
The DM24 outputs data through its DATA OUT port. This is a
standard RS232 serial link, outputting data in GCF format according to
the particular configuration of the instrument. The DM24 has a default
baud rate of 38,400. You can change this later using the BAUD
command or from Güralp Systems' control, acquisition and monitoring
software package, Scream! (see chapter 4).
A GPS connector is also provided on the front panel for attaching to a
GPS receiver. GPS signals are sent to both digitizers simultaneously,
but only the one to which it is directly attached can control the GPS
system.
The DATA IN port can be used to access the digitizer's console over a
direct serial link, or for inputting additional data streams for
transmission in GCF format.
Finally, the DM24 can be supplied with an optional USB client
interface for connecting to a PC. When this is present, the USB port
acts as a direct replacement for the DATA OUT or console port, and
appears as an additional serial port to your computer. You can
configure which port is replaced from the digitizer console (see
chapter 5).
FireWire disks
The optional IEEE.1394 (“FireWire”) ports on the DM24 may be used
to download data onto a compatible hard disk. The unit can be
supplied either with standard FireWire connectors or with robust milspec plugs (see Section 8.5, page 117, for pinout details).
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CMG-DM24
Before you can use the disk, you will need to reset it. The DM24 saves
data on the hard disk in a special format, so you cannot use your PC's
operating system to reset the disk.
You can use the DM24 itself, Scream!, or gcfxtract software to reset
the disk. For instructions on using Scream! and gcfxtract, please
see the documentation for these software packages, or their on-line
help.
To reset a FireWire disk with the DM24:
1. Power up the DM24, and connect it to your computer's serial
port.
2. Open its terminal console. To do this using Güralp Systems'
Scream! software, right-click on the digitizer's icon (once it
appears) and select Terminal.... From a Güralp DCM, issue the
command minicom -n port-number.
3. Issue the command DISKMENU. You will see the message
Plug in FireWire cable
4. Plug in your disk. The DM24 will output (on the console)
information about the disk as soon as it is detected.
5. Within the next 7 seconds, press any key to bring up the disk
menu.
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6. Press R to reset the disk.
7. When the reset is complete, remove the disk.
You will now be able to download data onto the disk when required.
2.4 The DM24BH borehole digitizer
When the DM24 is ordered in borehole form, it is supplied with a
surface interface unit for installation at the top of the borehole. This
unit takes the single data cable from the downhole digitizer and
provides standard connections for other equipment.
The connectors provided are:
• a SENSOR connector - a 10-way mil-spec socket carrying serial
data, GPS and power to the sensor;
• a GPS connector for attaching to your GPS receiver; and
• a POWER / HOLELOCK connector which can either be connected
to a source of 12 – 30 V power for supplying to the borehole
instrumentation (including sensors), or to a Holelock Control
Unit for driving the sensor's hole lock motors. It is not usual to
power the sensor and hole lock simultaneously; once the hole
lock is engaged, you should remove the Holelock Control Unit
and cabling so that the sensor cannot be removed.
• On the reverse side, a standard 9-pin RS232 connector is
provided for connecting to a PC running Scream! using a
straight-through serial cable.
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CMG-DM24
• There is also a three-pin mains (outlet) plug, which can power
the downhole instrumentation from 110 – 250 V AC as required.
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3 Using the DM24
Once the DM24 is connected to your equipment, it will start producing
data immediately. You can now start configuring it for your own
needs. There are two ways you can do this:
• using the graphical interface provided by Scream!, or
• over a terminal connection (see Chapter 5, page 51).
Both methods provide full access to the configuration options of the
digitizer.
In most circumstances, you will use Scream! to operate the system. For
complete information on how to use Scream! to configure and control
your instrument, please refer to the Scream! user guide.
3.1 Taps
The DM24 converts analogue signals to digital data at a high sample
rate, which is then reduced in steps. This process is known as
decimation, and each output stage is called a tap.
The highest data rate you can choose is 1000 samples/s. This rate can
only be produced by Tap 0, the first tap. Tap 0 can also produce data
at 500, 400, 200 or 100 samples/s.
After Tap 0 there are three more taps. Each tap produces data at an
integer sample rate, which must be 2, 4, 5, 8 or 10 times lower than the
previous tap.
For example, the following is a possible sequence:
Tap 0 : 500 samples/s
Tap 1 : 50 samples/s (divide by 10)
Tap 2 : 10 samples/s (divide by 5)
Tap 3 : 5 samples/s (divide by 2)
The digitizer always generates all four sample rates, but it does not
have to output them. You can configure any set of taps to output. You
can also have different taps configured for different sensor
components.
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CMG-DM24
All of these configuration options are easily changed via Scream!, or
you can use the terminal commands SET-TAPS and CONTINUOUS.
Triggering
The DM24 has a flexible triggering system. When the digitizer triggers,
it can optionally output (or store – see DUAL mode on page 16)
additional data. Any combination of tap and component can be output
as the result of a trigger.
In the example above, you might configure the sensor to output Tap 2
data (at 10 samples/s) continuously, but when a trigger is declared, to
output Tap 0 data (at 500 samples/s) as well.
Using triggering helps you to use limited storage capacity or
bandwidth more effectively.
The digitizer can look at the data from any tap to decide if a trigger has
occurred, including taps which it does not output. Which tap you
choose depends on the frequencies you want the trigger system to be
most sensitive to.
There are three types of trigger.
• A LEVEL trigger occurs when the absolute sample values exceed
a configured value.
The commands GTRIGGERS, MICROG, and HIGHPASS control
LEVEL triggering.
• An STA/LTA trigger occurs when the ratio of a short-term
average to a long-term average for recent data exceeds a
configured value.
The commands TRIGGERS, TRIGGERED, STA, LTA, RATIOS, and
BANDPASS control STA/LTA triggering.
• A software trigger occurs when you issue the command
S/WTRIGGER.
The DM24 can output data streams for a period of time before the
trigger starts, and after the trigger ends. The commands PRE-TRIG and
POST-TRIG set these time periods.
Triggering options can also be configured through Scream!.
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3.2 Streams
The DM24 organizes the data it produces into streams. Each stream
has a 6-character identifier. The first four characters are taken from the
System ID of the digitizer. When you receive the instrument, the
System ID is set to its serial number, but you can change it in Scream!
or with a terminal command.
The next character denotes the component or output type:
• Z, N, and E denote the vertical, north/south, and east/west
components respectively.
• X denotes the fourth full-rate data channel, which is provided
for connection to your own monitoring equipment via the
AUXILIARY connector (if present).
• C denotes the calibration input channel, which replaces the X
streams whilst calibration is in progress.
• M denotes one of the 16 slow-rate Mux (multiplex) channels.
Three of these (M8, M9 and MA) are used to report the sensor
mass positions. Channels MC and MD are connected to the X and
Y axes of the downhole inclinometer.
• For Z, N, E, X, and C streams, the last character represents the
output tap. Taps correspond to stages in the decimation process
within the digitizer, allowing the DM24 to output several
different data rates simultaneously. There are four taps,
numbered 0 to 3; 0 has the highest data rate and 3 the lowest.
Data streams end in 0, 2, 4 and 6 for taps 0, 1, 2 and 3
respectively.
If you configure the DM24 to output triggered data, this will
appear in separate streams ending with the letters G, I, K or M
for taps 0, 1, 2 and 3 respectively.
The DM24 also generates a stream ending 00. This is a status stream
containing useful diagnostic information, in plain text form (see
Section 6.1, page 89).
Digitizers for multiple instruments
The standard DM24 has 4 full-rate channels: one per component of a
triaxial instrument, plus the auxiliary and calibration channel.
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CMG-DM24
Some DM24 modules, known as “6-channel digitizers”, are designed
for use with two instruments simultaneously, connected to the ports
SENSOR A and SENSOR B. These digitizers actually have 7 full rate
data channels, including the auxiliary/calibration channel. When you
enable calibration on these digitizers, the signal is passed to both
instruments. All 7 channels share the same settings for the four output
taps.
A 6-channel digitizer will output full-rate streams with the following
final characters:
Z/N/E0
SENSOR A at tap 0
Z/N/E1
SENSOR B at tap 0
Z/N/E2
SENSOR A at tap 1
Z/N/E3
SENSOR B at tap 1
Z/N/E4
SENSOR A at tap 2
Z/N/E5
SENSOR B at tap 2
Z/N/E6
SENSOR A at tap 3
Z/N/E7
SENSOR B at tap 3
Z/N/EG
SENSOR A at tap 0,
triggered
Z/N/EH
SENSOR B at tap 0,
triggered
Z/N/EI
SENSOR A at tap 1,
triggered
Z/N/EJ
SENSOR B at tap 1,
triggered
Z/N/EK
SENSOR A at tap 2,
triggered
Z/N/EL
SENSOR B at tap 2,
triggered
Z/N/EM
SENSOR A at tap 3,
triggered
Z/N/EN
SENSOR B at tap 3,
triggered
X/C0
Auxiliary at tap 0
X/C1
Auxiliary at tap 1
X/C2
Auxiliary at tap 2
X/C3
Auxiliary at tap 3
Standard 6-channel digitizers have the same 8 Mux channels as their
3-channel counterparts: M8, M9 and MA for the mass positions of
SENSOR A, and MB to MF for your own equipment. These digitizers are
designed for use with a strong-motion instrument or geophone
attached to SENSOR B, and so do not expose the mass positions for
this sensor. In addition, SENSOR B cannot be locked, unlocked, or
centred.
Optionally, a digitizer can be supplied which provides 5 additional
Mux channels M3 to M7 for external equipment (again exposed on the
AUXILIARY connector). 6-channel DM24 modules with this option also
measure the mass positions of SENSOR B, if available, and output
these on streams ending M0, 1 and 2.
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3.3 Transmission modes
Transmission modes are an important concept on the DM24. The
current transmission mode determines whether the unit stores data in
its on-board Flash memory, sends it over the serial link in GCF format
or does some combination of these.
You can switch between transmission modes with a console command
(see chapter 5, page 51) or by using the Scream! configuration
interface.
DIRECT
Command: DIRECT
Instructs the DM24 not to use Flash memory for storage. Instead, all
data is transmitted directly to clients. An instrument in DIRECT mode
still honours the GCF Block Recovery Protocol: a temporary RAM
buffer always holds the last 256 blocks generated and, if a client fails
to receive a block, it can request its retransmission.
If you expect breaks in communication between the instrument and its
client to last more than 256 blocks, or if you want the instrument to
handle breaks in transmission (rather than relying on the client to
request missed blocks), you should use
• ADAPTIVE mode, if you want data to stay as near to real time as
possible (but do not mind if blocks are received out of order) or
• FIFO mode, if you need blocks to be received in strict order (but
do not mind if the instrument takes a while to catch up to real
time).
FILING
Command: FILING
Instructs the DM24 not to transmit blocks to clients automatically, but
to store all digitized data in the Flash memory. If you have chosen the
RECYCLE buffering mode (see below), the memory is used in circular
fashion, i.e. if it becomes full, incoming blocks begin overwriting the
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CMG-DM24
oldest in memory. If, instead, the WRITE-ONCE buffering mode is
active, the instrument will switch to DIRECT mode (see above) when
the memory becomes full.
You can retrieve blocks from an instrument in FILING mode by
connecting to its terminal interface and issuing commands such as
FLUSH, or through Scream! (see below).
Heartbeat messages
When in FILING mode, an instrument transmits “heartbeat” messages
over its data port. These short messages take the place of data blocks,
and ensure that programs such as Scream! know that an instrument is
present.
You can change the frequency of heartbeat messages from Scream!'s
Control window, or with the command HEARTBEAT.
DUPLICATE
Command: DUPLICATE
Instructs the DM24 to transmit streams directly to clients as for
DIRECT mode, but also to store all data into Flash storage as for
FILING mode.
If a client fails to acknowledge a block, the digitizer does not attempt
to retransmit it.
DUAL
Command: DUAL
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Instructs the DM24 to transmit any continuous streams directly to
clients as for DIRECT mode, but to store triggered data into Flash
storage as for FILING mode.
If you choose DUAL mode but do not select any continuous streams for
output, the instrument will send heartbeat messages as for FILING
mode. Scream! can pick these up and download new data as
necessary.
FIFO (First In First Out)
Command: FIFO
Instructs the DM24 to begin writing blocks to Flash memory as for
FILING mode, but also to transmit data to clients. Data is transmitted
in strict order, oldest first; the DM24 will only transmit the next block
when it receives an explicit acknowledgement of the previous block.
If the communications link is only marginally faster than the data rate,
it will take some time to catch up with the real-time data after an
outage. If you want data to be transmitted in real-time where possible,
but are worried about possible breaks in communication, you should
use ADAPTIVE mode instead.
FIFO mode will consider a data block successfully transmitted once it
has received an acknowledgement from the next device in the chain. If
there are several devices between you and the instrument, you will
need to set up the mode for each device (if applicable) to ensure that
data flow works the way you expect.
Like all the transmission modes, FIFO mode does not delete data once
it has been transmitted. You can still request anything in the Flash
memory using Scream! or over the command line. The only way data
can be deleted is if it is overwritten (in the RECYCLE buffering mode,
see below) or if you delete it manually.
ADAPTIVE
Command: ADAPTIVE
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CMG-DM24
Instructs the DM24 to transmit current blocks to clients if possible, but
to store all unacknowledged blocks in the Flash memory and re-send
them, oldest first, when time allows. ADAPTIVE mode is best suited for
“real-time” installations where the link between digitizer and client is
intermittent or difficult of access.
If the communications link is only marginally faster than the data rate,
it will usually be busy transmitting real-time data. Thus, it may take a
while for the instrument to work through the missed blocks. In this
case, and if your client supports it, you may prefer to use the Block
Recovery Protocol to request missed blocks where possible (see
section 7.3, page 110).
Some software packages (most commonly Earthworm) cannot handle
blocks being received out of time order. If you are using such a
package, ADAPTIVE mode will not work and may crash the software.
Buffering modes
There are two different buffering modes which affect how the internal
flash memory is utilized. Either may be used with any of the available
transmission modes.
RE-USE / RECYCLE
Command: RE-USE
Instructs the DM24 to carry on using the current transmission mode
when the Flash memory becomes full, overwriting the oldest data
held. This buffering mode is called RECYCLE in Scream! and on the
DCM.
For example, in DUAL mode with RECYCLE buffering, the latest
continuous data will be transmitted to you as normal, and the latest
triggered data may be retrieved from the Flash memory using Scream!
or the command line. However, if you do not download data regularly
from the Flash memory, you may lose older blocks. This mode thus
lets you define the end point of the data held by the instrument.
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WRITE-ONCE
Command: WRITE-ONCE
Instructs the DM24 to stop writing data to the Flash memory when it is
full, and to switch to DIRECT mode automatically.
For example, in FIFO mode with WRITE-ONCE buffering, the station
will transmit data to you continuously, but also save it in the Flash
memory until it is full. Once full, the instrument will switch to
DIRECT mode and continue transmitting, though no further data will
be saved. This mode thus lets you define the start point of the data
held by the instrument.
3.4 Downloading stored data
If you choose a transmission mode where data is stored in Flash
memory, you will need to recover this data at a later date. You can do
this either over the serial link or using the DM24's FireWire interface.
Downloading over FireWire
To download data over FireWire, plug the disk in and issue the
command DISKMENU from the digitizer's console. The digitizer 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 R 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 N then ENTER,
or wait for 10 seconds. The DM24 will transfer any data it has
recorded since the last download and then mark this data 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 5.9, page 77, for more information.
The DM24 checks for a FireWire disk when it boots up. If there is
enough new data waiting to be transferred (by default 128 Mb), the
DM24 will automatically transfer it onto the disk. The digitizer then
updates its internal pointers to mark this data as already downloaded.
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CMG-DM24
This feature is particularly useful for autonomous installations: after
the digitizer 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 power (from a 12 Volt supply). If you interrupt a transfer whilst it is
in progress, the digitizer 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.
Downloading over the serial link
To download data over the serial link:
1. Open the digitizer's console. To do this using Güralp Systems'
Scream! software, right-click on the digitizer's icon (once it
appears) and select Terminal.... From a Güralp DCM, issue the
command minicom -n port-number.
2. If you want to download all data held in the Flash memory,
issue the command
ALL-FLASH ALL-DATA DOWNLOAD
3. Alternatively, select a particular set of streams, sample rates and
times to download using the STREAM, S/S, FROM-TIME and TO-
TIME commands, and finish with DOWNLOAD. See Section 5.9,
page 77, for more details.
4. Issue the GO command to start transferring data. If you are
using Scream! or a DCM, closing the terminal session will have
the same effect.
3.5 Reading DM24 disks
When the DM24 saves data onto a FireWire disk, it uses a special
format called DFD.
You can read this 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
DCM data module, which uses a FAT32-compatible journalling file
system.
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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).
To read a disk using gcfxtract:
1. Attach the disk to your computer. You can use FireWire,
USB, or any other interface supported by your computer and
the disk.
2. Run gcfxtract and select the required disk from the dropdown list, then click Scan.
gcfxtract will scan the disk and display all the streams it
finds in the selection area below. For each stream, the Stream
ID and the number of blocks found are shown.
This operation requires roughly 12 Mb of available memory
for every Gb of space on the disk. If you have a very large
disk, your computer may have to use its hard disk to make
enough space. This will slow down scanning considerably.
3. By default, all streams containing more than 100 blocks are
selected for extraction. You can change which streams to
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extract by checking or un-checking the check box beside each
stream.
You can check or un-check all of the boxes using the Select
all and Unselect all buttons. Clicking Invert checks all
unchecked boxes, and un-checks all checked boxes.
4. Enter a path name into the Target Directory field, or use the
Browse... button to find a directory. This will be used as the
root directory for extracted data. If it does not exist, gcfxtract
will create it.
5. Enter a format string into the Filename Format field. The
syntax is the same as the format string in Scream! and full
documentation is available by pressing the '?' button beside
the format entry field in interactive mode.
6. Normally, gcfxtract outputs GCF files, to ensure all the
information in the original data is retained. If you want to
convert to a different format, select it from the Output Data
Format drop-down box. gcfxtract can output in most of the
formats supported by Scream!.
7. Data is automatically placed in time order and saved in
multiple files, each file containing a contiguous segment of
data. By default, data streams are recorded in files 60 minutes
long. To change this to some other number of minutes, alter
the value in the Data File Duration (mins) box.
For data streams, if there is a gap in the data, gcfxtract will
start a new file anyway.
Status streams are also saved in in multiple files, but have a
default length of 24 hours. To change this, alter the value
under Status File Duration (hours).
8. When you are happy with the settings, click Extract to begin
extracting the data.
9. Clicking Reset sets a flag on the disk which marks it as
empty. Next time a digitizer wants to transfer data, it will
begin at the beginning of the disk, overwriting the old data.
When this happens, none of the old data can be extracted
with gcfxtract or Scream!. Until then, however, you will still
be able to retrieve all the data.
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10. When you are finished, you should exit gcfxtract and then
use your operating system's standard facility for un-mounting
hardware (e.g. “Safely Remove Hardware” under Windows)
before disconnecting the drive.
You can also read disks with Scream!. This allows you to view data in
the process of being transferred, but is slightly slower, because
Scream! does not read data in strict order. To read a disk with
Scream!:
1. Attach the disk to your computer. You can use FireWire, USB,
or any other interface supported by both your PC and the disk.
2. Run Scream!, and select File → Setup... from the main menu.
Select the Files tab.
3. Set the Base Directory, Filename Format and Data Format as
described above. Also, if required, set the Post-processor and
Granularity options to suit your requirements. Consult the
Scream! documentation for details.
4. Select the Recording tab, and check Auto Record—Enable for
Data Streams and Auto Record—Enable for Status Streams.
Click OK. Scream! will remember the recording options you set
in steps 3 and 4 for later occasions.
5. Select File Read SCSI disk... → from the main menu. Scream!
will search for attached disks, and open a window with a list of
all the streams it has found.
6. Select the streams you want to replay, and click Open. The disk
will appear in the left-hand pane of Scream!'s main window,
and the streams you have selected will start playing into the
stream buffer, as well as being recorded.
7. When you have finished transferring the data, if you want to
reset the disk, select File Reset SCSI disk... → from Scream!'s
main menu. Select the disk you want to reset, and click OK.
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3.6 DM24 USB Host Operations
DM24 Mk3 USB host option
This interface enables the DM24 to record GCF data to a standard USB
disk drive or Flash memory stick using the ISO 9293 FAT filing
format – readable by Linux, DOS, Windows and Mac OS.
Equipment fitted with the USB Host Port connector (labelled
USB BOMS – Bulk Only Mass Storage) will automatically record the
current real time data to the USB device when it is plugged in.
To do this, the DM24 should be in DIRECT or DUPLICATE
transmission mode so that real time data is being fed to the standard
transmit buffer used for normal serial data transmission. The USB
process runs in parallel with the serial transmit thread using the data
in the transmit buffer. It does not matter whether the serial port is
connected or not.
Other transmission modes do not pass useful data via the serial port
and so cannot be used with USB devices. In particular FILING mode
saves all data to the internal flash memory (for later download via the
serial port or FireWire interface) and only outputs “heartbeat” status to
the serial port to inform systems monitoring the port that the unit is
present and operating. FIFO and ADAPTIVE modes use the internal
flash as an extension to the serial transmit buffer as explained in
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section 3.3, on page 15. As no contiguous streams are sent via the
serial port in these modes, nothing will be written to the USB device.
To record data to a USB device, the system should be configured in
DIRECT or DUPLICATE mode – in DUPLICATE+REUSE mode the
DM24 will always have the last 64Mb or more of data in its internal
flash – the firmware does not currently support transferring data from
the DM24 internal flash to a USB device.
Formatting a USB device
If you wish to use a USB device it must be formatted with 16 Kilobyte
clusters. In Windows 2000, XP and Vista open a command prompt and
type:
format e: /fs:fat32 /a:16k
replacing e with the letter of the drive which you wish to format.
Directory structure
The system creates the following directory (folder) structure:
The main directory is \GURALP
Beneath this is a sub-directory named after the DM24's system ID (e.g.
GSLA) within which will be a further sub-directory for each stream the
system is configured to produce. For example:
C838Z2 tap2, vertical component at selected sample rate
C838M8 vertical component mass position
C83800 the digitizer's status stream
Data for each stream is recorded as files within the corresponding subdirectory. The file name is simply the date and time of the first sample
in the file, given in the format YYMMDDHH.xxxx
For example:
08102314.gcf 2008 Oct 23 14:00 – data file
08102312.txt 2008 Oct 23 12:00 – status/text file
The amount of data in each file (granularity) depends on both the
stream sample-rate and type. It can be configured using the
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CMG-DM24
HOURFILES command, which takes four parameters (which precede
the command – see chapter 5, page 51 for details of the DM24's
internal FORTH interpreter):
FAST SPS SLOW STATUS HOURFILES
FAST specifies the file size, in hours, for sample rates ≥ SPS
SLOW is the size, in hours, for lower sample rates < SPS
STATUS is the size, in hours, for status stream files.
The default settings are:
1 40 4 12 HOURFILES
With these settings, the system will start a new file every hour for
streams with a sample rate ≥ 40 samples per second.
Lower sample rate streams will have files which last 4 hours – so the
file names will have the sequence “YYMMDD00, YYMMDD04,
YYMMDD08” etc.
Status files will have 12 hour granularity i.e. “YYMMDD00 and
YYMMDD12”.
Note that status streams are recorded as plain text files with the
extension '.txt'.
All other streams are recorded with the extension '.gcf' which is the
same format used by 'Scream!' (i.e. a series of 1k 'gcf' data blocks),
consequently the files can be viewed and processed by Scream!,
simply by “drag and dropping” or right-clicking to select the option.
Due to bandwidth and processing limitations, it may not always be
possible to record continuous streams with particularly high sample
rates. Note that when triggers are in use, the sample rates of streams
transmitted over the serial port will typically increase considerably. If
your application involves sample rates higher than 250 samples per
second, you should verify to your own satisfaction correct operation
(under triggered conditions, if necessary) with your own USB devices
before permanent installation.
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System operation
USB memory sticks and disk drives normally have an LED indicating
activity. This will flash as each block is written, so a few flashes every
10 seconds would be expected from a DM24 producing 100 sps data.
Since data blocks are recorded to their corresponding files in real time,
only the current/latest block can be lost when a USB stick is detached;
all other stream files will have been closed/saved.
When a USB stick is plugged in, the system interrogates it to
determine the free space. This operation can take a minute or more
depending on the capacity of the USB device. When the operation has
been completed, the system reports the available space using the LCD
and, also, in the status stream, as in the example below:
2008 10 3 13:18:49 USB Flash stick Recording started NO NAME
D:/>
USB File granularity :
For sample rates >= 40 sps : 1 hour files otherwise 4 hour files
except status ; 12 hour files
2008 10 3 13:19:52 USB Stick space remaining 3.9GB
The system will regularly (after each 5MB of data storage – typically an
hour or 2 of running) report the space available in GB/MB and as a
predicted duration in days/hours (based on the utilization rate for the
previous 5MB).
Recording to a USB device stops automatically when there is less than
100k free space. To record more data, the device must be replaced with
a freshly formatted one.
USB devices can be removed/replaced at any time, but the system does
not additionally buffer the data so a small amount will be lost during
the changeover. In DUPLICATE mode all data would also still be in the
internal flash.
An example of a status display is shown below. This is taken from the
status stream (*00) of a DM24 fitted with a USB host controller after
several minutes of operation.
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CMG-DM24
Note for v103 Build 78 firmware.
This build displays additional status information on the LCD panel to
show when the USB stick is being written to and when it is not being
accessed.
It is recommended that the memory stick is only removed when the
display shows USB free, which is followed by a bar graph
indicating a 5 second countdown.
The USB device should not be removed while the display shows
USB BUSY WAIT or while it is scrolling the earlier status
information.
When the stick is initially inserted the LCD panel will report, after a
short delay, access to the stick. This is while the system is calculating
the free space available, which may take many tens of seconds.
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4 Using Scream!
Scream! is a versatile seismic data visualisation program for Güralp
instruments which runs on Windows and Linux computers. If a
DM24's DATA OUT port is connected to an RS232 port on a computer
running Scream!, the program can be used to analyze digitized data
from the DM24's connected analogue sensors, and to control/configure
both the digitizer and the sensors themselves. Scream can also work
with network-attached digitizers.
Scream! is available for free download from Güralp Systems, or may
have been supplied with your equipment.
4.1 Configuring digitizers
Scream! distinguishes between configuration and control of digitizers.
The most important difference is that a digitizer may be controlled
through Scream! at any time whilst it is acquiring data, whereas
configuration options only take effect after a reboot (with consequent
loss of data).
To change the configuration of any connected digitizer:
1. Locate the digitizer you want to configure. All connected
digitizers have an entry in the tree on the left of Scream!'s main
window. If the digitizer is transmitting data through a remote
server or DCM, you may need to “unroll” the entry for that
server (by clicking on the icon) to see the digitizers connected
to it.
2. Right-click on the digitizer's entry (not the icon for the server or
any Comxx icon). Digitizers are shown with icons depicting a
coloured cylinder.
3. Click Configure.... Scream! will then contact the digitizer and
retrieve its current configuration, a process which will take a
few seconds. This done, the Configuration setup window will be
displayed.
4. Once you are happy with any changes you have made in the
Configuration Setup window, click UPLOAD to send them to the
digitizer and reboot. This will take a short while.
To control a digitizer whilst it is running, either right-click on the
digitizer's entry in the list and click Control..., or double-click the
entry. In either case Scream! will contact the digitizer to retrieve
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CMG-DM24
control information and display the Control window. The options you
can control immediately are:
• the type of sensor you are using;
• GPS power cycling options;
• the short-term and long-term average values for triggering (but
not which streams perform the trigger, or which are output by
it);
• the length of pre-trigger and post-trigger periods;
• calibration signal options; and
• mass control functions.
Some of these options can also be altered in the Configuration setup
window. For more information on the Control window, see Section 4.2,
page 44.
If you need a more powerful interface to the DM24, you can also issue
commands to it directly using Scream!'s terminal mode. A terminal
window is opened by right-clicking on the digitizer's entry in the list
and selecting Terminal.... The digitizer will stop transmitting data
while you have a terminal window open. Data collected whilst the
terminal is active will be stored for transmission later, memory space
permitting.
The remaining sections of this chapter describe in detail the
configuration options available for the DM24.
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