Chapter 5. Getting started

To start using the Scream! AVD extension, it is necessary to:

• Specify the GCF data servers from which to receive data, the network port-number used to receive that data and the network port-number to use to transmit the calculated data streams;

• Specify the location of the Scream! calibration values file (calvals.txt);

• Select the streams to be processed;

• Change the output stream names (if necessary).

This chapter describes these operations.

5.1 Specifying ports and GCF data servers

The network ports and GCF data servers are specified on the Network Settings form. To open this form, select Settings then Network settings on the main menu or type +, then . The form is shown below:

The port numbers and the location of Scream's calibration file all need to be configured before data can be received, processed and transmitted properly.

5.1.1 “Pull” servers

If you wish Scream! AVD to pull data from GCF sources, the IP addresses or DNS names of the servers should be entered here. For each, enter the IP address or DNS name, followed by a colon (':') and then the appropriate UDP port number. Each server should be entered on a separate line. Once the settings are applied, Scream! AVD will immediately start attempting to pull data from these sources.

5.1.2 “Push” servers

If you wish to have GCF data sources pushing data to Scream! AVD, specify the UDP port number that you wish to use for this purpose in the Rx port field. If you do not intend to use “push” servers, this field can be left at its default value.

5.1.3 Scream! Port

Scream! AVD pushes its output data to Scream! (or another client) on the same PC via the UDP port specified in the Scream! port field. This number must match the value specified as Port used for all network communications at the bottom of Scream!'s Network Control window.

5.2 Calibration values (calvals.txt) file location

The calibration-values file (calvals.txt) location should be entered in the Network Settings form as shown in section 5.1.

The full path to the file and the file name need to be entered. Click the button to navigate to the file or type in the full path and file name.

This setting (along with a correctly-populated calvals.txt file) is required for Scream! AVD to work properly.

5.3 Instrument selection

Once the network details have been entered, the Scream! AVD application can automatically populate the left-hand list of the main window based on the data from the configured servers. To enable this, tick the Add check-box as shown in the following image.

Instruments will automatically be added to the left-hand list of the main form as GCF data blocks are received by the application.

As instruments are added to the list, the calibration file (calvals.txt) is used to determine what type of instrument it is: whether acceleration, velocity or displacement. If the instrument type cannot be determined, either because the calvals.txt file is not found or there is not a correctly formed “response” line for the instrument, the corresponding line in the list will be highlighted in yellow.

The instruments that are added to the list can be filtered using a filter string, an example of which ([abc]*) is shown in the image above. Only instruments with names matching this filter will be added to the list. If the filter string is incorrect in any way, the edit box will be highlighted in yellow and the Add check-box will remain un-ticked. Please see section 8.1 for more information about the use of the filter string.

The button will remove all entries from the left-hand list.

As instruments are added to the left-hand list, they can be moved across to the right-hand list – i.e. marked for inclusion in the processing - using the top two buttons in the centre of the main form.

The top button will move all the instruments to the right-hand list. The button will move only the selected instruments.

The bottom two buttons behave in a similar manner. The button moves the instruments selected in the right-hand list to the left and the button moves all the instruments back to the left.

5.4 Output streams

GCF streams are identified by unique Stream Names which are formed by the concatenation of the SysID (the system identifier, which identifies a single digitiser, which may have one or more connected instruments), a hyphen ('-') and the Stream ID. For more information about Stream Names, please see www.guralp.com/howtos/stream-ids-explained.shtml.

Scream! AVD generates new Stream Names for every stream that it outputs, although the automatically-generated names can be edited if desired.

When instruments have been enabled (moved to the right-hand list), Scream! AVD creates new default SysIDs for the pass-through stream and for each of the calculated streams. The types – whether acceleration, velocity or displacement - of the calculated streams are dependent on each instrument's type:

• For an accelerometer, new velocity and displacement streams will be generated;

• For a velocimeter, new acceleration and displacement streams will be generated;

• For a displacement meter, new velocity and acceleration streams will be generated.

In each case, the original input streams are also passed through. optionally with a new SysID, although the time-series data are unchanged.

Default Stream Names are created by modifying the SysID by appending or prepending either P for pass-through; A for acceleration, V for velocity or D for displacement. (Only three of these four will be shown for any given input.) The operator can choose between appending and prepending via the Default naming… screen (see section 6.4 on page 14). Existing SysIDs are truncated as necessary to make room for the new character.

In the example below, input data come from an accelerometer with a SysID of AAA. The input data are passed through unchanged with a new SysID of AAAP (P=pass-through) and two new streams are generated: a calculated velocity stream with a SysID of AAAV (V=velocity) and a calculated displacement stream with a SysID of AAAD (D=displacement).

The Stream IDs, which identify the instrument, the component and the decimation tap (sample rate) are unchanged by default, although they can also be edited if desired.

The Stream Names generated as described above can be inspected and edited by selecting the source instrument in the right-hand instrument list. The following information appears in the right-hand pane of the main window:

SysIDs and Stream IDs can be edited in this pane. In order to avoid duplicate stream names, checks are made during editing. If a name is already in use, either with the current instrument or with another, the relevant edit box will be highlighted in yellow and the “update” button will be disabled, as shown:

By default, all three output streams are enabled when an instrument is first added to the right-hand list. Each can be disabled (or re-enabled) by clicking on the appropriate check-box, as seen on the left in the image above.