Chapter 5. Configuring the DM16
Scream! is a versatile seismic data visualisation program for Güralp instruments, and is available for free download from Güralp Systems, or may have been supplied with your equipment.
You can use Scream! to change the configuration of your digitizer through an easy-to-use graphical interface. All of the configuration options of the DM16 are supported by Scream!, including output control and triggering.
5.1 Configuring with Scream!
Scream! 4 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:
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.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.
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.
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 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 how to use Scream! to configure your digitizer, please see the Scream! user guide or the on-line help.
If you need a more powerful interface to the DM16, 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.
5.2 Terminal commands
You can connect to the internal software of the DM16 over its output serial port and communicate with it.
To enter command mode from Scream!, right-click on the digitizer's icon and select Terminal... from the menu that pops up. A window will open, and once the digitizer and computer are communicating properly you will see the prompt
ok
If you prefer, you can use a terminal program on your computer (such as minicom on Linux, or hypertrm on Microsoft Windows) to connect to the DM16.
Whilst you are in terminal mode, data transfer will be interrupted; the digitizer may use any Flash memory as a temporary store, depending on how you have configured it. Some commands, such as SET-TAPS, require a reboot to take effect.
Güralp DCM and AM modules also allow you to send commands direct to the digitizer using the command-line tool gcli. For more information, please see the manual for your data module.
If you have problems connecting to the digitizer's console, you should check that the serial port's options and baud rate are set correctly in Scream! or your terminal program. As supplied, the DM16 expects connections at 38400 baud, with 8 data bits, no parity bit and 1 stop bit. No flow control is used.
The DM16 uses FORTH to implement its features. To issue a command in FORTH, you must supply the arguments before the command, for example:
3 SENSOR-TYPE
In FORTH, anything you enter is termed a word. New words (case insensitive) are placed on a stack. Some words are known to the system, and may represent commands; if a command finds itself at the top of the stack (e.g. because it is the last thing you typed), they will execute, remove themselves from the stack, and then remove further items from the stack to use as arguments. Thus, in the command
3 SENSOR-TYPE
the 3 has no immediate effect, so stays on the stack; SENSOR-TYPE takes itself and the previous item (here 3) off the stack, then performs its action on the 3 (here, setting the configured sensor type to 3, representing a CMG-3T sensor.)
If a command completes with nothing remaining on the stack, the digitizer will show the prompt ok. Otherwise, the prompt will remind you that the digitizer is waiting for you to complete the command. Some commands, such as SAMPLES/SEC, clear the stack automatically after they execute.
Some commands are interactive, and will ask you to provide extra information after you execute them. In the following sections, interactive commands are shown as example sessions, where information you enter is given in medium and messages returning from the DM16 are given in bold.
5.3 Getting help
HELP
Syntax: HELP
Displays help about the DM16's terminal commands.
5.4 General configuration
Syntax: SET-ID (interactive)
Sets the system identifier and serial number of the DM16 to values you supply.
SET-ID
System Identifier ? (e.g. ALPHA,) DM16, Serial # ? (e.g. 1234,00) 4507,00
The system identifier you supply may contain up to 5 alphanumeric (0-9A-Z) characters, and must have a comma after it.
The serial number you supply must contain exactly 6 alphanumeric (0-9A-Z) characters, and must include a comma after the fourth character.
Syntax: type SENSOR-TYPE
Tells the DM16 which kind of sensor is attached to it. This affects whether or not the digitizer exposes commands such as locking and centring.
type can be one of
1, for CMG-40T sensors,
2, for CMG-3ESP sensors,
3, for CMG-3T analogue sensors, or
4, for CMG-3TD sensors.
Syntax: type GPS-TYPE
Tells the DM16 which kind of GPS is attached to it.
type can be one of
0, if no GPS is available, or
2, for attached GPS equipment using the NMEA protocol.
SET-CLOCK
Syntax: SET-CLOCK (interactive)
Sets the internal clock.
SET-CLOCK
Enter Date & Time -
YYYY MM DD HH MM SS
2006 02 01 12 53 25 Clock set to 2006 2 1 12:53:27 ok_SBHY
The time should be entered in the form year month day hour minute second, padding each field with zeroes so that they line up with the guide above.
If the DM16 does not recognize the time format you have used, it will output the message Invalid Time Entry.
This setting will be overridden when the GPS system next synchronizes the clock.
TIME?
Syntax: TIME?
Displays the current date and time.
LEAPSECOND
Syntax: yyyy mm dd LEAPSECOND
Manually notify the digitizer of an upcoming leap second. This command is not normally necessary, since GPS already has support for leap seconds. However, some units do not properly interpret the GPS signals. See SQPATCH, below.
The leap second is taken to be at the end of the day yyyy-mm-dd.
SQPATCH
Syntax: SQPATCH ENABLE or SQPATCH DISABLE
Enables or disables the internal patch for older GPS receivers based on Trimble Lassen SQ units. These units misinterpret the GPS system's advance notification of a leap second, and consequently run one second slow until the leap second occurs.
With SQPATCH enabled, the time reported by the digitizer is offset by 1 second to counteract this problem. If you have set LEAPSECOND, above, SQPATCH will automatically be disabled when the leap second occurs, and the digitizer will then run normally.
GPS receivers with the latest firmware do not suffer from this problem.
To find out whether SQPATCH is currently enabled, issue the command
.SQPATCH
Syntax: port baud-rate BAUD
Sets the baud rate for one of the serial ports on the DM16, in bytes per second. port can be
0, for the DATA OUT port, or
1, for the GPS port.
For example,
0 38400 BAUD
1 4800 BAUD
This will reset a standard DM16 to its default configuration.
The allowable values for baud-rate are 4800, 7200, 9600, 14400, 19200, 38400, 57600 and 115200. For compatibility reasons, 1152 is also accepted, setting the baud rate to 115200.
GPS inputs should always be set to 4800 baud.
Syntax: RE-BOOT (interactive)
Causes the DM24 to reset after a delay of 2 s.
RE-BOOT
Confirm with 'y' ? y
Responding to the confirmation message with anything other than y will abort the reset.
5.5 Output configuration
Syntax: tap-0 tap-1 tap-2 tap-3 samples/sec
The DSP software on the DM16 supports up to 7 cascaded filter/decimation stages. At each stage, the sample rate can be decimated by a factor of 2, 4 or 5. The ADC within the unit outputs data at 2000 samples/sec, so decimated data streams are available from 1,000, 500 and 400 samples/sec down to 1 sample/sec.
You can specify the sample rate to use at four of these stages, known as taps. You can also take output from any of these four stages. The DM16 will arrange the remaining stages according to your settings.
The arguments tap-0 to tap-3 are the sample rates at each tap in turn, starting with the highest. You must ensure that each rate is lower than the previous one by a factor of 2, 4, 5, 8 (= 2 then 4), 10 (= 2 then 5) or 16 (= 4 then 4). Non-integer values are not allowed.
For example:
1000 125 25 5 samples/sec
1000 500 100 10 samples/sec
500 100 20 4 samples/sec
400 40 10 5 samples/sec
As long as you specify the initial taps, you can omit later ones. The command fills in the value of the missing taps, using a decimation factor of 2 where possible. Thus, the following commands are equivalent:
400 40 20 10 samples/sec
400 40 samples/sec
Currently the DM software does not support the new GCF format for higher sample rates. It also does not properly support 250 samples/s, nor rates below 1 sample/s.
Syntax: tap components CONTINUOUS
Sets which components are output under normal conditions, and at which tap(s).
tap is the tap number at which to output the triggered stream. You can set which taps output which sample rate using the SAMPLES/SEC command, described above.
components is an integer below 16, whose binary bits represent the Z (1), N (2), E (4) and auxiliary (8) components respectively. Thus, for example,
0 1 CONTINUOUS will output the Z component only (1) at the first tap;
0 2 CONTINUOUS will output the N component only (2);
0 4 CONTINUOUS will output the E component only (4);
0 7 CONTINUOUS will output all three directional components (1 + 2 + 4 = 7);
0 12 CONTINUOUS will output the E component and the auxiliary component (4 + 8 = 12);
0 0 CONTINUOUS will output nothing at this tap.
To set triggered output streams, you should use the TRIGGERED command detailed below.
5.6 Triggering
Syntax: components TRIGGERS
Selects which component or components can generate an STA/LTA trigger. Only these components will be examined by the triggering algorithm.
components is an integer below 16, whose binary bits represent the Z (1), N (2), E (4) and auxiliary (8) components respectively as described above. Issuing 0 TRIGGERS will disable the triggering system.
Syntax: tap components TRIGGERED
Selects which component or components will be output when a trigger is generated, and at which tap (sample rate).
tap is the tap number at which to output the triggered stream. You can set which taps output which sample rate using the SAMPLES/SEC command, described above.
components is an integer below 16, which represents which components to output in the same fashion as in the CONTINUOUS command, above.
(This command and the previous one have similar names; remember that a component TRIGGERS the system, whilst taps and components are TRIGGERED.)
Syntax: Z-secs N-secs E-secs X-secs STA
Sets the length of the “short-term” averaging period in the STA/LTA triggering algorithm.
Z-secs, N-secs, E-secs and X-secs are the time period over which to calculate the average for the Z, N, E, and auxiliary components respectively. If a component is not considered by the triggering algorithm (see TRIGGERS, above), the value you specify here will be ignored.
For example, 1 1 2 2 STA will calculate short-term averages over 1 s for the Z and N components, and over 2 s for the E and auxiliary components.
If you issue STA with only one argument, it is used for all four components. For example, 5 STA will calculate averages over 5 s of all components.
Syntax: Z-secs N-secs E-secs X-secs LTA
Sets the length of the “long-term” averaging period in the STA/LTA triggering algorithm.
Z-secs, N-secs, E-secs and X-secs are the time period over which to calculate the average for the Z, N, E, and auxiliary components respectively. If a component is not considered by the triggering algorithm (see TRIGGERS, above), the value you specify here will be ignored.
For example, 15 20 20 20 STA will calculate long-term averages over 15 s for the Z component, and over 20 s for the N, E and auxiliary components.
If you issue STA with only one argument, it is used for all four components. For example, 5 STA will calculate averages over 5 s of all components.
Syntax: Z-ratio N-ratio E-ratio X-ratio RATIOS
Sets the ratio of STA to LTA above which a trigger will be declared in the STA/LTA triggering algorithm.
Z-ratio, N-ratio, E-ratio and X-ratio are the time period over which to calculate the average for the Z, N, E, and auxiliary components respectively. If a component is not considered by the triggering algorithm (see TRIGGERS, above), the value you specify here will be ignored.
For example, 4 10 10 10 RATIOS will cause the DM16 to trigger if the STA/LTA ratio is above 4 for the Z component, or above 10 for the remaining components.
BANDPASS
Syntax: tap filter BANDPASS
Instructs the DM16 to pass the stream(s) which generate STA/LTA triggers through a band-pass filter before examining them. The corner frequency of the band-pass filter is determined from tap and filter:
filter = 1 creates a filter with a corner at 10 % of the Nyquist frequency for tap tap (i.e. 5 % of its sample rate)
filter = 2 creates a filter with a corner at 20 % of the Nyquist frequency for tap tap (i.e. 15 % of its sample rate)
filter = 5 creates a filter with a corner at 50 % of the Nyquist frequency for tap tap (i.e. 25 % of its sample rate)
When LOWLATENCY is active, this command is used to set the tap used as the source of low-latency data. Data from this tap is decimated inside the DSP, and output on a separate stream at a rate 10 times slower than the configured rate.
MICROG
Syntax: level MICROG
Sets the output level above which a trigger will be declared in the LEVEL triggering algorithm. level is measured in counts.
HIGHPASS
Syntax: filter HIGHPASS
Instructs the DM16 to pass the stream(s) which generate LEVEL triggers through a high-pass filter before examining them. filter can be
1, for a 100 s high pass filter,
2, for a 300 s filter,
3, for a 1000 s filter, or
0, to disable the high pass filter.
Syntax: time PRE-TRIG
Sets the pre-trigger recording time. time is the number of seconds of data to output from before a trigger is declared.
Syntax: time POST-TRIG
Sets the post-trigger recording time. time is the number of seconds of data to output after a trigger condition lapses. If an event persists for some time, all triggering components must fall below the threshold before the trigger condition will lapse; only then will the post-trigger period begin.