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Untelemetered Deployments with 3TDs, 40TDs, 5TDs and 6TDs

For un-telemetered installations with 3TDs and other Güralp *TD instruments, it is possible to connect a Güralp ruggedised hard drive to the instrument and configure the instrument's digitiser to power up the drive at regular intervals, write all outstanding data and then power down the drive again. This increases the amount of data that can be stored between site visits.

Pre-deployment checks

The following steps should be carried out in the lab before you leave for the deployment.

Connect the drive to the instrument and, in Scream, right-click on the digitiser icon in Scream's source tree and select _Terminal from the context menu. Enter the DISKMENU command and check that the disk powers up and is recognised by the digitiser. Select option D to check that there is nothing already on the disk and option R to clear it if there are any existing data-files.

Divide the capacity of the disk (in megabytes) by 510 and issue the MBTRANSFER command , replacing nn with the answer. For example, if you have a 250 MB disk, issue 49 MBTRANSFER - this ensures optimum disk utilisation. Note that the system must have enough FLASH memory fitted to accommodate the amount of data specified by the MBTRANSFER setting. You can see how much FLASH memory is fitted when you open the terminal, as described below. Memory upgrades are available if required.

Use Scream's _Configure menu to set up the desired sample rates, set the Transmission Mode to DIRECT and the Buffering Mode to RE-USE (details about data flow modes). Open a WaveView window and check that you are receiving data and that the system synchronises correctly to GPS.

Use Scream's _Configure menu and change the Transmission Mode to FILING. Data transmission will stop although the instrument will start emitting heartbeat messages at regular intervals (details).

Open a Terminal as before. The digitiser will display a summary of FLASH memory usage. Type GO to close the window, wait a few minutes and then repeat. Confirm by the difference in usage figures that data are being written to FLASH.

Wait for some data to accumulate, open a Terminal again and enter the command DISKMENU. Take option N to save new data. Wait until the process completes and then use GCFXTRACT ( to verify that data have been written correctly to the disk.

If all of this has worked correctly, then you should be able to deploy the instrument as you wish. If you want to convince yourself that the automatic writing-to-disk works correctly, you can temporarily set MBTRANSFER to a low value, such as 1 MB (command: 1 MBTRANSFER), and then let the system accumulate data until an automatic write occurs. This might take some time: if you are recording three 100 sps streams, it could take over an hour, depending on the compressibility of the data. Once you believe that a write should have taken place, you can check both that there are data on the disk and that the FLASH usage figures, as seen in the terminal, have been reset.

After testing, always reset the disk. You can only write to it 510 times between resets, which may limit how much data you can store during a deployment.

Deployment check-list

Once at the deployment site: