Guralp Systems Limited
MAN-T60-0002 - 6TD Operator's Guide

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1. Preliminary Notes 2. Introduction 3. First encounters 4. Installing the 6TD 5. Configuration with Scream! 6. Calibrating the 6TD 7. Command-line interface 8. Updating the 6TD 9. Connector pin-outs 10. Specifications 11. Revision history

Section Index: 4.1. Handling notes 4.2. Connections 4.3. Installation notes 4.4. Installing in vaults 4.5. Installing in pits 4.6. Other installation methods 4.7. Rapid installation 4.8. Recovery 4.9. Networking overview 4.10. Setting up the Ethernet interface 4.11. Setting up wireless networking 4.12. Configuring the built-in digitiser 4.13. Downloading stored data 4.14. Receiving data in Scream!

Chapter 4. Installing the 6TD

4.1 Handling notes

Caution: Although it has a rugged design, the 6TD is still a sensitive instrument, and is easily damaged if mishandled. If you are at all unsure about the handling or installation of the device, you should contact Güralp Systems for assistance.

Observe the following precautions:

Note: All parts of the 6TD are waterproof.

4.2 Connections

4.2.1 The instrument

The 6TD's output connectors are all located on the sensor lid. The sensor can be supplied with a number of options, so not all of the connectors described here may be present on your instrument.

All 6TD instruments have a nineteen-pin bayonet connector which carries power, data and GPS signals. The supplied breakout box (see below) provides individual connectors for these, or you can make up your own cable if you prefer.

The 6TD may also have connectors for the FireWire, Ethernet or Wi-Fi interfaces.

The connectors for the FireWire and Ethernet options are both six-pin bayonet plugs. If the labelling has become illegible for any reason, they can be distinguished by noting that the FireWire connector lies to the East of the instrument and the Ethernet connector to the North-East, as in the picture below (which shows an early, unlabelled prototype unit).

4.2.2 The break-out box

In addition to the cable to the instrument, which is moulded into the case, the breakout box provides

You may need to attach a suitable connector to the power cable provided. The 6TD draws a nominal current of 75 mA from a 12 V supply when in use. A 12 V, 25 Ah heavy-duty sealed lead-acid battery will, therefore, operate the instrument for around a week without recharging.

4.3 Installation notes

For the best possible results, a seismometer should be installed on a seismic pier in a specially-built vault, where conditions are near perfect. Here, wave-trains arriving at the instrument reflect very well the internal motion of subsurface rock formations. However, this is not always feasible. For example,

In these situations, the seismometer and its emplacement need to be considered as a mechanical system, which will have its own vibrational modes and resonances. These frequencies should be raised as high as possible so that they do not interfere with true ground motion: ideally, beyond the range of the instrument. This is done by

In temporary installations, environmental factors are also important. The sensor needs to be well protected against

This can be done by selecting a suitable site, and placing the instrument in a protective enclosure. An open-sided box of 5 cm expanded polystyrene slabs, placed over the instrument and taped down to exclude draughts, makes an excellent thermal shield.

After installation, the instrument case and mounting surface will slowly return to the local temperature, and settle in their positions. This will take around four hours from the time installation is completed.

4.4 Installing in vaults

You can install a 6TD in an existing seismic vault with the following procedure:

4.5 Installing in pits

For outdoor installations, high-quality results can be obtained by constructing a seismic pit.

pit-cutaway-bedrock

Depending on the time and resources available, this type of installation can suit all kinds of deployment, from rapid temporary installations to medium-term telemetered stations.

Ideally, the sensor should rest directly on the bedrock for maximum coupling to surface movements. However, if bedrock cannot be reached, good results can be obtained by placing the sensor on a granite pier on a bed of dry sand.

4.6 Other installation methods

The recommended installation methods have been extensively tested in a wide range of situations. However, past practice in seismometer installation has varied widely.

Some installations introduce a layer of ceramic tiles between a rock or concrete plinth and the seismometer (left):

pit-installation-with-tiles pit-installation-with-tiles-removed

However, noise tests show that this method of installation is significantly inferior to the same concrete plinth with the tiles removed (right). Horizontal sensors show shifting due to moisture trapped between the concrete and tiling, whilst the vertical sensors show pings as the tile settles.

Other installations have been attempted with the instrument encased in plaster of Paris, or some other hard-setting compound (left):

installation-in-plaster-of-paris installation-in-sand

Again, this method produces inferior bonding to the instrument, and moisture becomes trapped between the hard surfaces. We recommend the use of fine dry sand (right) contained in a box if necessary, which can also insulate the instrument against convection currents and temperature changes. Sand has the further advantage of being very easy to install, requiring no preparation.

Finally, many pit installations have a large space around the seismometer, covered with a wooden roof. Large air-filled cavities are susceptible to currents which produce lower-frequency vibrations, and sharp edges and corners can give rise to turbulence. We recommend that a wooden box is placed around the sensor to protect it from these currents. Once in the box, the emplacement may be backfilled with fresh turf to insulate it from vibrations at the surface, or simply roofed as before.

By following these guidelines, you will ensure that your seismic installation is ready to produce the highest quality data.

4.7 Rapid installation

The 6TD is specially designed for rapid installation, and may be fully installed in a few hours. This section details a method of deploying 6TD instruments with the minimum of additional equipment. This is recommended for situations where seismic instrumentation needs to be installed very quickly, e.g. to study a resumption of volcanic activity, or where difficulty of access to the site prevents you from constructing a full seismic pit. You should always construct a pit if possible (see section 4.5), since the data produced will be of significantly higher quality.

4.8 Recovery

Care should be taken when recovering the 6TD, since tapping or banging it can cause damage to the sensors inside. The following instructions assume that you have installed the instrument following the steps above.

4.9 Networking overview

The 6TD can optionally be supplied with no networking, with a wired Ethernet connection or with both wired and wireless Ethernet connections.

Additional information about both modules is obtainable from Lantronix's web-site: www.lantronix.com.

The Lantronix modules are both twin-channel serial-to-TCP converters. Channel one's serial interface is exposed on the instrument's main connector; this can be used to provide networking capabilities to any external device with an RS232-compatible output. Channel two is internally connected to the standard digitiser output in such a way that, if a serial device (such as a terminal emulator) is detected on the DATA OUT port, the networking module is disconnected. Hence, networking is only available when the DATA OUT port is disconnected.

Note: Note that the wired and wireless capabilities of the WiPort are also mutually exclusive: only one can be active at a time and, indeed, the wireless interface cannot even be configured when the device is in wired mode.

The illustration above shows serial data in blue, network data in yellow and power connections in red.

The Lantronix module can be powered down with the CD24 command

ETHER DISABLE

and powered up with the command

ETHER ENABLE

Certain operations, such as a firmware upgrade, can result in power to the Lantronix module being turned off. In these cases, the ETHER ENABLE command should be used to restore power.

4.10 Setting up the Ethernet interface

6TD instruments with Ethernet features installed use an embedded Lantronix WiPort-NR module to provide the network interface. This module can be configured using a built-in Web server.

Before you can access the Web server, however, you will need to assign the device an IP address. This can be done using Lantronix' DeviceInstaller utility for Microsoft Windows, or using a DHCP server. You will need a PC with a network interface installed.

4.10.1 Using DeviceInstaller

4.10.2 Using DHCP

If you cannot install DeviceInstaller on your PC, or do not wish to, you can also get access to the 6TD using a standard DHCP server. In most cases you will need to have administrative privileges to do this.

4.10.3 Configuration with the Web interface

Once you have access to the WiPort-NR's Web interface, you can configure it with its proper settings. Unless you have previously configured password protection, simply click if prompted for a user name and password.

4.11 Setting up wireless networking

6TD instruments with wireless features installed use an embedded Lantronix WiPort module to provide the network interface. This module can be configured using the DeviceInstaller utility for Microsoft Windows, or using a DHCP server. You will need a PC with a wireless card installed.

You may find it easiest to gather together all the Wi-Fi hardware before taking it into the field, and configuring it from a local wireless-enabled PC.

6TD instruments with the wireless networking option also have an ETHERNET port for attaching to a wired network. You can switch between the wired and wireless interfaces using DeviceInstaller.

Note: There are two types of wireless network topology supported by the WiPort, infrastructure and ad-hoc. GSL can only support 6TDs running in infrastructure mode.

4.11.1 Using DeviceInstaller

4.11.2 Using DHCP

If you cannot install DeviceInstaller on your PC, or do not wish to, you can also get access to the 6TD using a standard DHCP server. In most cases you will need to have administrative privileges to do this.

4.11.3 Configuration with the Web interface

Once you have access to the WiPort's Web interface, you can configure it with its proper settings. Unless you have previously configured password protection, simply click if prompted for a user name and password.

4.11.4 Installing wireless hardware

The small antenna supplied with the 6TD is adequate for initial testing or temporary installations with an access point within 50 metres of the instrument.

To send data over a larger distance, or if the line of sight between the antenna and the access point is blocked, you will need to use a larger and more powerful antenna.

You can reduce the power requirements by using a directional antenna pointed at the location of the access point. The access point does not need to be permanently present. For example, you could set up an array of 6TD instruments with antennas pointed towards a prominent natural feature with a direct line of sight to all the instruments, and access them all from this location using a laptop PC.

4.12 Configuring the built-in digitiser

Autonomous 6TD installations will need to be configured before deployment. You can do this either

Both methods provide full access to the configuration options of the built-in digitiser.

In particular, 6TD can operate in a number of filing modes. These modes determine whether the unit stores data in its on-board Flash memory, sends them over the serial link in GCF format, or does some combination of these. See section 5.2.4 for more details.

4.13 Downloading stored data

If you choose a transmission mode where data are stored in Flash memory, you can recover these data at a later date, using either the FireWire interface or a serial link.

Note: The FireWire interface is very much faster than the serial link: the serial link is only really useful for small, ad-hoc transfers.

The Flash memory is used as a ring buffer. Two pointers into the memory keep track of where data were last read (the “Read Pointer”) and last written (the “Write pointer”). When either pointer reaches the end of physical memory, it wraps round back to the beginning. The behaviour when the write pointer reaches the read pointer (i.e. when the memory becomes full of data, none of which have been downloaded) is governed by the commands RE-USE/RECYCLE and WRITE-ONCE, described in section 5.2.6.

This rest of section 4.13 describes downloading data over FireWire to a hard drive (section 4.13.1), reading the data from the hard drive onto a PC (section 4.13.2) and downloading data over a serial port or Ethernet interface (section 4.13.3).

4.13.1 Downloading data over FireWire

The easiest way to download data over Firewire is to connect a suitable disk to the FireWire port of the 6TD and power cycle the instrument.

Note: The 6TD requires the disk to be in DFD format. If the disk has not previously been used with a 6TD (or 3ESPCD), it must first be initialised: see section 7.8.13 for details. Once initialised the first time, it can then be reinitialised in the same way or, from within Scream, by selecting File → Reset SCSI disk... from the main menu

If you have ordered a 6TD with the powered FireWire option, you can attach the disk directly to the 6TD with no additional connections. Otherwise, you will need to connect the disk to a power source through the supplied adapter.

When the sensor restarts, it will automatically the disk and flush all new data to it.

If you do not want to restart the instrument, you can also flush data to disk manually:

4.13.2 Reading 6TD disks

The 6TD uses a special disk format, DFD, for recording data. This format is also used by other Güralp digitisers such as the DM24.

You can read this data into a PC using Scream! or the gcfxtract utility, which are freely available from the Güralp Systems Web site.

Note: The DFD format is not the same as that used by the Güralp Systems EAM data module, which uses an ext3, ext4 or a FAT32-compatible journalling file system.

Güralp Systems can provide fully-tested 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:

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!:

4.13.3 Downloading data over the serial port or Ethernet interface

Start by configuring Scream to record all incoming data by visiting the “Recording” tab of the File→Setup dialogue:

Ensure that the first four check-boxes are ticked. Next, switch to the “Files” tab and choose an appropriate base directory, file format and filename format.

Click to save your changes and close the dialogue.

Next, open a connection to the digitiser's console. To do this using Güralp Systems' Scream! software, right-click on the digitiser's icon () and select Terminal…. From a Güralp EAM, issue the command

data-terminal

and select the appropriate data source from the menu.

To simply download all data held in the Flash memory, issue the command

ALL-FLASH ALL-DATA DOWNLOAD

followed by

GO

This will initiate a complete download. The ALL-FLASH and ALL-DATA commands act as modifers to tell the system whhat to download.

If you wish to download only a subset of data, you can replace the ALL-FLASH and ALL-DATA modifiers with other modifers to select different streams and/or time periods:

The parameters are illustrated in the diagram below. If you miss out a parameter, DOWNLOAD will re-use the value you last specified.

The DOWNLOAD command returns immediately, so that you can issue more commands if required. To close the connection and begin downloading with the specified selectors, issue the GO command.

Note: You can pause a download by entering terminal mode, and either restart with another GO or abort with END-DOWNLOAD.

When you complete a DOWNLOAD without specifying a time period, the CD24 adjusts the internal read pointer to mark the latest position. This is then used as the start point for the next DOWNLOAD with the command ALL-TIMES.

The various modifiers are described in detail in section 7.8.

Once the GO command has been issued, the window may close, depennding on which eulator you are using. On an EAM, the data-terminal (minicom) session is closed by keying +, then .

4.14 Receiving data in Scream!

There are several ways a 6TD instrument can connect to Scream!:

To connect to a 6TD over the network:

PreviousNext

1. Preliminary Notes 2. Introduction 3. First encounters 4. Installing the 6TD 5. Configuration with Scream! 6. Calibrating the 6TD 7. Command-line interface 8. Updating the 6TD 9. Connector pin-outs 10. Specifications 11. Revision history