The main window

When you start Scream!, you will be shown an empty main window:

Scream! is now ready for you to start adding data sources.

Serial ports

• Select File → Setup.... If the Com Ports tab is not visible, bring it to the front.

  If you are running Scream! for the first time, this window will automatically appear, together with a short tutorial.

  

• The serial ports available to Scream! are listed in the table. Identify each port, and the instrument connected to it.

  If you are using Microsoft Windows, the Port number corresponds to the COMn number of the serial port.

  If you are using Linux, Port numbers 1 – 64 refer to the built-in serial ports /dev/ttyS0 – /dev/ttyS63, and 65 and above to USB-connected serial ports beginning /dev/ttyUSB0.

  A port may not be listed if it is not installed, or suitable drivers are not available, or if another program is using it. Scream! scans your computer for new ports each time you open the Setup window. To make Scream! scan the ports again, click the Port column heading.

• Configure each port according to the settings of the instruments connected to them:

  Baud Rate : The speed of the serial link to the instrument. 3-channel Güralp digitizers default to a speed of 9600; 6-channel digitizers, to 19200. DCM units use a baud rate of 115200 by default. If you do not know the baud rate of your digitizer's output port, select Auto-Detect from the drop-down menu to have Scream! attempt to detect it for you. The instrument must be producing data for this to work.

  You can set all ports to the same baud rate by clicking on the column heading and choosing a suitable value from the drop-down menu.

  If you are using Scream! for real time data, you will not need to change any of the remaining settings.

  AutoBaud : Once connected, Scream! dynamically alters its baud rate to fit with the instrument to which it is connected. However, this can interfere with transmission over very noisy links. If you have problems, clear this box.

  ACKs : Whether Scream! should send Acknowledged messages to this instrument.

  NACKs : Whether Scream! should send Not Acknowledged messages to this instrument, when it detects a failure in transmission.

  BRP : Whether Scream! should attempt to recover dropped blocks from the instrument using the Güralp Block Recovery Protocol. You should clear this box if you are using a single-direction (simplex) communications link.

  If you uncheck all three boxes (ACKs, NACKs and BRP), Scream! will never acknowledge data packets that it is sent. This is particularly useful in situations where you need to connect to a digitizer without altering the flow of data. For example, a digitizer in FIFO or ADAPTIVE mode will normally save data in Flash memory only if data packets are not acknowledged. When you come to download the saved data from such a digitizer, you should uncheck these boxes before connecting the digitizer. Doing this will ensure that incoming data continues to be saved on the digitizer, rather than transmitted to Scream!.

  Rx T/O (receive timeout) : The time, in seconds, that Scream! will wait for the sender to finish transmitting a block, before assuming that it is complete. If the instrument stops transmitting in the middle of a block, Scream!'s diagnostics will detect it and request retransmission next time the instrument is online.

  You can set or unset all the check boxes in a column by clicking on the column heading.

• Click OK.

If any instruments are connected, data streams should now begin appearing in the right-hand portion of Scream's main window.

Another way to configure a serial port is to right-click on its entry in the streams list (the left-hand panel in the main window) and selecting Configure... However, you can only do this if data has already arrived through the port, making it appear in the streams list.

If you want to access Scream! servers on the network (i.e. DCMs, or other instances of Scream!), you will need to add the servers to the list using the Network Control window. See Section 4.1, page 47, for more details.

Scream! will remember all the data sources you have specified on exit. When you next open the program, it will automatically try to re-establish all the connections.

The stream buffer

Scream! works by recording incoming streams into a fixed area of memory, called the stream buffer. All of Scream!'s operations work with the data in this buffer.

When you start Scream! for the first time, this buffer is empty. You can add data to it either by receiving it from local serial ports, connecting to Scream! network servers, or replaying GCF files.

Once the stream buffer is full, Scream! will start discarding the oldest data. If you have not told Scream! to record the incoming streams (see Chapter 8, page 90), then you will not be able to get discarded data back.

You can change the size of the stream buffer in the Display pane of the Setup window (see Section 3.4, page 43.)

If you have enabled GCF recording, Scream! keeps track of the files which contain data in the stream buffer, and saves this information in a .lst file in the current recording directory. When Scream! is restarted, it reads this file and tries to rebuild the stream buffer as it was when it was shut down. Otherwise, the buffer starts off empty as before.

The source tree

The tree in the left panel of the main window shows all the data sources currently connected to Scream!, whether local instruments, networked instruments, or files being replayed.

Scream!'s source tree has two main parts: Files, which contains all the files you have replayed (including automatic replay: see Section 8.3, page 101), and Network, which represents your seismic network.

Beneath Network is a list of all the network servers Scream! is connected to, plus the entry Local for your computer's own serial ports.

The next layer contains the serial ports themselves. These icons are provided to help you identify the instruments, as well as providing direct terminal access.

As an example, the screen shot above shows Scream! running on a computer which is not directly attached to any instruments. It receives data from a single network source, MACALLAN1, which has two serial ports Com1 and Com2. These ports are attached to the instruments BHOLE-BH05 and GURALP-DA79 respectively: if your installation uses a CRM (Combiner-Repeater Module) or DCM connected to a serial port, several instruments may be listed under a single serial port icon.

The MACALLAN1 server icon has been “unrolled” to reveal the serial port icons. You can “roll up” icons and save space by clicking on the box.

You can tell Scream! to ignore a particular instrument by right-clicking on its icon and selecting Ignore. When you do this, Scream! will discard any blocks it receives from the instrument. They will not appear in the stream buffer or be recorded to disk. Select Ignore again to stop ignoring the instrument.

Icons

Instrument icons change colour to provide you with a quick overview of the instrument's timing and mass position status:

If both halves of the instrument icon are clear , Scream! has not received any information from the instrument since the program started.

If the top half is green , the instrument has reported a satisfactory timing fix.

If the top half is yellow , the instrument has reported a gap in the timing stream. This will occur if the GPS signal deteriorates to the point where the receiver cannot keep a lock on the satellites.

If the top half is red , the instrument has not reported a satisfactory timing fix for over an hour. This will happen if the instrument has reported failures (as above), but also if it has not reported anything. If you have set the GPS system to power down for intervals longer than an hour, the icon will turn red even if the system is working normally.

If the bottom half is red , the instrument (or one of its components) is running with a mass position over 15000 counts—roughly 50% of its travel. You should re-centre the component if possible, to avoid clipping after large ground movements.

If the instrument appears as a green box , the instrument has sent status blocks to Scream!, but no data. The box represents a Güralp CRM/SAM; these modules store or forward data from other instruments, but occasionally produce status blocks themselves. If a digitizer produces a status block before any data, perhaps because you have configured very slow data rates, or are using FILING or DUAL filing modes (see Section 7.5, page 83), it will temporarily appear with this icon.

The stream list

If Network is selected in the source tree, the right-hand panel will list all the data streams which Scream! receives (and is not ignoring.) If an entry in the source tree is selected, the stream list will only show the streams beneath that entry—selecting a serial port will only show streams from instruments connected to that port, and so on.

The columns in the table provide useful information about each stream.

Stream ID : A unique name for the data stream, being a combination of six letters A – Z and numbers 0 – 9. The first four characters of this name identify the digitizer, and the last two characters identify the individual stream.

The first four characters are set by default to the serial number of the digitizer; you can change this on the System ID pane of the Configuration Setup window (see Section 6.1, page 69) or from the digitizer's console.

The last two characters tell you the type, component, and output tap of the stream.

• Z0, N0, E0 correspond to input channels Z, N, and E of the digitizer's SENSOR A port, continuously output through Tap 0.

• Z2, N2, E2 correspond to the same input channels, output through Tap 1 at a lower sample rate.

• Likewise, Z4, N4, E4 and Z6, N6, E6 correspond to Taps 2 and 3.

• Z1, N1, E1; Z3, N3, E3; Z5, N5, E5; and Z7, N7, E7 correspond to Taps 0, 1, 2, and 3 of SENSOR B, when you connect a 6-channel digitizer.

• 00 is the digitizer status stream (notice: zero sample rate).

• M8, M9, MA are slow-rate Mux channels reporting the sensor mass positions for the Z, N, and E components (Section 6.4, page 77.)

• MB is a slow-rate Mux channel used for user input, or calibration signals on older Güralp Systems digitizers.

• MC-F are further Mux channels, used for user input or the digitizer's internal temperature.

• X0-X7 denote the auxiliary analogue input channel on newer DM24 units, digitized using the same tap settings as Z, N and E.

• C0-C7 denote the same input channel, when it is being used for an input calibration signal.

• Z, N, EG-N are the channels Z, N, E0-7, respectively, when they output triggered data.

• IB denotes digitizer Information Blocks containing user information. Scream! tries to interpret these blocks and automatically extracts data from them for use in WaveView windows or Matlab extenstions.

• CD, BP are digitizer streams for specialised use.

Scream! can replace these designations with more helpful names if you wish: see Section 3.4, page 44.

Rec. : Whether Scream! is currently recording the data stream to the laptop's onboard hard disk. If another device on your network is recording the data stream independently of Scream!, the entry in this column will still be No.

Comp. : The compression factor of the data in the stream, expressed as the number of bits occupied by each record (8, 16 or 32 bits.)

SPS : The sampling rate of the data stream, in samples per second. Status streams, ending in 00, do not constantly output data and have an SPS of 0. By default, the stream list is sorted in order of sample rate, with the status streams at the bottom.

End time and Date : the date and time of the most recent data, as measured by the data's own timestamp. This is not necessarily the latest data to arrive.

RIC : The ‘Reverse Integrating Constant’. In effect this is the value of the last sample received. This is most useful for reading mass positions or other environmental streams. Status streams have a RIC of zero.

You can hide the extended information about each stream by selecting View → List from the menu. To return to the full view, select View → Details.

Sorting options

Sorting options are available from the View → Sort By → menu:

Alphabetical : Strict alphabetical order, 0 – 9 then A(a) – Z(z).

Component : Vertical components (ending Zx), followed by Nx and Ex components, then Mux channels Mx. Within a component type, sort by the first four characters of the Stream ID.

Instrument : Sort by the first four characters of the Stream ID. Within an instrument, sort by tap, then by component.

Sample Rate : Sort by sample rate, highest to lowest. Within a sample rate, sort as Instrument.

Tap : Sort by tap (the last character of the Stream ID.) Within a tap, sort by instrument, then by component.

Select the Reversed option to reverse any of these sort orders.

You can also sort the list by Stream ID or SPS by clicking on the relevant heading; click again to reverse the sort order.

The status bar

At the bottom of Scream!'s main window is a status bar containing summary information about Scream!'s state:

• The number of different data streams currently accessible from the window, including those that have been “rolled up”.

• The amount of memory currently being used by Scream!'s stream buffer. You can change the maximum size of the stream buffer from the Setup window (see Section 3.4, page 43.) If this number approaches the capacity of your computer, it may become slow and difficult to use.

• The current time, according to the local computer (not the timestamps of incoming data.)

To disable the status bar, deselect View → Status Bar on the menu.

Viewing streams

Double-click on one of the streams to open a window for viewing the data, or right-click on it and select View.... Alternatively, make a selection of streams from the list and double-click on the selection or press ENTER.

Data streams are opened in a Waveview window:

This window allows you to see real-time data coming in. You can also pause the window and examine any features held in the stream buffer. For full information on the features provided by Waveview windows, see Chapter 3, page 25.

Status streams (ending 00) consist of plain text. Double-clicking on a status stream produces the Status window:

The first blocks will give the boot message from the digitizer, including its software revision and the data streams selected for downloading and triggering. Later blocks give information on visible GPS satellites, the location of the GPS antenna and time synchronization status. Also displayed are the baud rates currently used for each channel and for the data link.

For more information on status streams and GPS, see Section 5.2, page 59.

If you View a selection which includes both status and data streams, the status streams will be collected together and displayed in a tabbed Status window, whilst the data streams will appear in a single Waveview window.

Connecting to instruments

Digitizer configuration and other common operations can be performed from Scream! by right-clicking on the digitizer in the source tree and selecting Configure... or Control... See Chapters 6 and 7 for more information.

Scream! also allows you to access the serial terminal of any connected digitizer and issue commands directly, by right-clicking on it and selecting Terminal.... See Section 5.1, page 56, for more information on the serial terminal.

An instrument may connected to Scream! through a series of other units (SAMs, DCMs, etc.) Scream! will negotiate with each unit in turn to reach the instrument you are interested in. However, the process may take a little time.

Right-clicking on a digitizer and selecting Triggers... brings up a window describing all the digitizer triggers that have been detected. This window can also be reached from the Summary window: see section 5.3, page 64.

Calibration data

Scream! can display data streams from displacement, velocity, and acceleration sensors in physical units. To be able to do this, it needs to know the calibration information provided with the sensor and digitizer.

Newer Güralp digitizers transmit calibration information in an information block when they reboot. When Scream! receives an information block that it understands, it automatically extracts this information and remembers it.

You can also enter and edit calibration information manually. Right-click on the digitizer's icon and select Calvals.... A window will open with a text entry box. This window lets you edit Scream!'s calibration values file.

Fill in the text box with calibration information for your digitizer and the instrument connected to it, in the format described below.

• To set the serial number of the instrument, include the line

  Serial-Nos=serial-number

  Scream! cannot tell what instrument is connected to the digitizer. This line is provided to help you remember which set of calibration values you have used, and to provide a title for calibration graphs. If you attach a different instrument to the same digitizer, you will need to enter new calibration values to reflect the new instrument.

• To set the sensitivity of the digitizer, include the line

  VPC=sensitivity

  VPC stands for voltage per count, measured in units of μV/count. This is sometimes given as μV/Bit on the digitizer calibration sheet.

• To set the sensitivity of the calibration channel, include the line

  CALVPC=sensitivity

  as for the other digitizer channels.

• To set the value of the calibration resistor, include the line

  CALRES=resistance

  Güralp Systems digitizers normally use a 51 kΩ resistor (CALRES=51000).

• To set the sensor type, include the line

  TYPE=model-number

  e.g. 3T, 5T, etc..

• To set the response of the sensor, include the line

  RESPONSE=response-type unit

  The values you can use are given in the table below.

Some English descriptions are also accepted, e.g. “120s velocity”, “100Hz acceleration”.

• To set the sensitivity (or gain) of the sensor components, include the line

  G=vertical-sensitivity,N/S-sensitivity,E/W-sensitivity

  These values are given on the sensor calibration sheet. For velocity sensors, they are given in units of V m–1 s (V/m/s). The gain of an accelerometer is expressed in V m–1 s2 (V/m/s2). Because Güralp Systems sensors and digitizers use differential inputs and outputs, the sensitivity is quoted as 2 × (single-ended sensitivity) on the calibration sheet.

• To set the coil constants of the sensor components, include the line

  COILCONST=vertical-coil-constant,N/S-coil-constant,E/W-coil-constant

  These values are given on the sensor calibration sheet.

• To set the local acceleration due to gravity, include the line

  GRAVITY=acceleration

  You should give this value in m s–2, if you know it. If you miss out this line, Scream! will use a standard average g value of 9.80665 m s–2.

When you have filled in all the values, click OK.

Any WaveView windows that are open will change to show streams in physical units. New WaveView windows will also use these units where possible.

Each digitizer System ID and serial number can have only one instrument connected to it. If you have a 6-channel digitizer with two connected sensors, you will need to make the digitizer announce different serial numbers for each one. On newer Güralp Systems DM24 digitizers, this can be done with the command SERIAL2. See the manual for your digitizer for more information.

Examples

The calibration information for a CMG-3T weak-motion velocity sensor might look like the following:

Serial-Nos=T3X99

VPC=3.153,3.147,3.159

G=1010,1007,1002

COILCONST=0.02575,0.01778,0.01774

CALVPC=3.161

CALRES=51000

TYPE=CMG-3T

RESPONSE=CMG-3_30S_50HZ V

GRAVITY=9.80122

CMG-5TD accelerometers use 1 Ω calibration resistors, and their coil constant is set to unity. Older CMG-5TD instruments, based on Mk2 digitizer hardware, do not have calibration input facilities, and thus the CALVPC entry is omitted. For example:

Serial-Nos=T5585

VPC=2.013,2.028,2.036

G=0.256,0.255,0.255

COILCONST=1,1,1

CALRES=1

TYPE=CMG-5T

RESPONSE=CMG-5_100HZ A

GRAVITY=9.81089

For information on the file, calvals.txt, which stores these values, see section 13.2, page 125.

Other features

The main menu also provides some miscellaneous facilities.

Choose File → Save Program State to save Scream!'s configuration file immediately. This file is read whenever you start Scream!, and any changes are written back whenever you close it. Under Microsoft Windows, the configuration file appears as scream.ini in the Windows directory; under Linux, it is saved in $HOME if this variable is set, otherwise the same directory as the Scream! program file. You can change the name of the configuration file with a command line option (see Section 13.1, page 124.)

Choose File → Application Caption... to change the title of Scream!'s main window. This is useful if you have several copies of Scream! running on the same computer (e.g. to run multiple network services.)

Choose View → Stay On Top to keep Scream!'s main window on top of all other Scream! windows at all times. Other applications may still cover Scream!'s main window.