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How to record mass-locking and unlocking operations

If you suspect problems with mass operations - unlocking, centring and locking - of Güralp 3-series instruments, Güralp support may request that you send GCF recordings illustrating the problem.  This page describes the sequence of actions required in order to make an effective, complete recording of these operations.


This page specifies the procedure if you are using a Minimus or Minmus+ digitiser as the recording device.

If, instead, you are testing a digital instrument containing a CD24 or DM24 digitiser, such as a 3TD, 3TDE, 3ESPCD or 3ESPCDE, or you are using a CD24 or DM24 digitiser (including DM24SxEAMs) as the recording device for your suspect instrument, click here to access instructions specific to your hardware.

The procedure

  1. Open the Scream program on a PC and key ctrl + N to open the Network Control window.

    Ensure that you are on the My Client tab and then right-click in an empty part of the Servers list (the top pane). Choose _Add TCP Server… from the context menu:

    Selecting 'Add TCP Server' from the context menu
  2. Type the I.P. address of the Minimus into the Add TCP Server window:

    The 'Add TCP Server' dialogue

    and click : A new entry will appear in the Servers list.

  3. Right-click on the new entry in the Servers list and select Connect from the context menu:

    selecting 'Connect' from the context menu

    Close the Network Control window and wait until the streams start appearing in Scream's main window:

    streams appearing in Scream's main window
  4. Set Scream to record streams into an empty directory, by choosing File → Setup → Files and entering an appropriate path in the field:

    putting the path of an empty directory into the 'Base directory' field
  5. While still on the Files tab, ensure that the Data Format is set to GCF:

    Setting the data format to 'GCF'

    then click the 'OK' button to close the Setup dialogue and save the configuration.

  6. In Scream's main window, click on the required instrument in the source tree (on the left):

    Selecting the instrument from Scream's source tree

    Check that streams have appeared for all three velocity components (those ending in Zn, Nn and En), and all three mass-position streams (those ending in M8, M9 and MA). If they are not all present, wait until they are - this might take a few minutes for the low sample-rate mass-position streams. Once they have all appeared, ensure that the word Yes appears in the Rec column for all of these and, if not, right-click the 'Rec' column-heading until all required channels are set to record:

  7. Double-click the digitiser's icon in the source tree:

    The digitiser's icon in Scream's source tree

    This will open the digitiser's web page in your web browser.

  8. Select the Setup tab and click the 'Unlock' button to attempt to unlock the masses:

    the Minimus' 'Setup' web page showing the location of the 'Unlock' button

    Note the time. Wait ten minutes for the operation to complete and the outputs to settle.

  9. If you are recording these data because you are having problems with mass centring, click the 'Centre' button to attempt to centre the masses:

    the Minimus' 'Setup' web page showing the location of the 'Centre' button

    Wait ten minutes for the operation to complete and the outputs to settle.  Repeat this step several times at ten minute intervals, noting the time at each step.

  10. Click the 'Lock' button to initiate a locking of the masses:

    the Minimus' 'Setup' web page showing the location of the 'Lock' button

    Note the time and then wait ten minutes for the operation to complete and the outputs to settle.

  11. Gently tap the side of the instrument with your finger-tip.

  12. Wait twenty minutes:  this is necessary because mass position channels (typically being output at at one sample per second) can take over sixteen minutes to assemble enough samples to fill a packet.

  13. In Scream’s main window, click the word 'Rec' in the column header for stream recording. Scream will prompt you Stop recording on ALL streams?:

    Scream's 'Stop recording on ALL streams?' prompt

    Click the 'Yes' button: this flushes all outstanding recording buffers to disk.

  14. View the files in the recording directory to check that all six are present (the three velocity channels and the three mass-position channels). In Windows, you can do this by selecting all the stream files, right-clicking and choosing View with Scream:

    Selecting 'View with Scream' from the Windows Explorer context menu

    This should open a WaveView window displaying the six traces:

    Checking the recordings before sending
  15. If you have recorded all three velocity streams and all three mass position streams, and you have verified that the recordings cover the entire experiment, attach all the files from your recording directory to an email - along with your notes of the exact timings of each unlock, centre or lock operation - and send it to , where it can be used for diagnosis.