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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:

If, instead, you are using a digitiser from the Minimus family, click here to access appropriate instructions.

The procedure

  1. Connect the digitiser to a PC running Scream.

  2. 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
  3. While still on the Files tab, ensure that the Data Format is set to GCF:

    Setting the data format to 'GCF'
  4. Change to the Recording tab and set Scream to automatically record all streams by ticking the first three check-boxes as shown:

    setting up automatic recording
  5. Power up (or power-cycle) the digitiser.  (This generates a lot of useful configuration and diagnostic information in the status stream.)

  6. Wait until the digitiser icon (Scream's digitiser icon) appears in Scream’s main window, if it is not there already.

  7. Right-click on the digitiser icon and select Configure:

    selecting 'Configure' from the digitiser's context menu
  8. Go to the Mux Channels tab and ensure that the check-boxes for M8, M9 and MA are ticked in the System SOH section.

    • If they are already ticked, click the 'Cancel' button
    • If they are clear (i.e. if they are not ticked): tick them, click the 'Upload' button and wait for the digitiser to reboot.
    Enabling the mux channels from the Configuration dialogue
  9. In the main window, check that streams have appeared for all three velocity components (those ending in Zn, Nn and En), all three mass-position streams (those ending in M8, M9 and MA) and the status stream (which ends in 00). 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 stream and select "Start recording".

    Ensure that all streams are being recorded
  10. Right-click on the digitiser icon (Scream's digitiser icon) and select Control:

    selecting 'Control' from the digitiser context menu in Scream
  11. Go to the Mass Control tab.

    When using a DM24, an additional check-box is displayed, labelled Monitor Progress. Ensure that this check-box is cleared before proceeding.

    Click the 'Unlock Now' button

    The 'Unlock Now' button on the 'Mass control' tab

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

  12. If you are recording these data because you are having problems with mass centring, click The 'Center Now' button and note the time:

    The 'Center' button on the 'Mass control' tab

    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.

  13. Click The 'Lock Now' button

    The 'Lock now' button on the 'Mass control' tab

    Close the Control dialogue and wait ten minutes for the operation to complete and the outputs to settle.

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

  15. 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.

  16. Right-click on the digitiser icon (Scream's digitiser icon) and select Terminal:

    selecting 'Terminal' from the digitiser context menu in Scream

    A terminal window should open.

  17. Key enter a few times to get the digitiser’s attention, then enter the command FLUSH-STATUS

  18. Enter the command GO – the terminal window should close:

    The terminal session closing after the 'GO' command
  19. In Scream’s main window, click the word Rec in the column header for stream recording.

  20. 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. (You can re-enable them immediately if you wish to continue recording for any reason.)

  21. View the files in the recording directory to check that they are all present (the three velocity channels, the three mass-position channels and the status stream).  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 Windwos Explorer context menu

    This should open a WaveView window with at least six traces and a status-viewing window:

    Checking the recordings before sending
  22. If you have recorded all three velocity streams, all three mass position streams and the status stream, and you have verified that the recordings cover the entire experiment, attach all the files from your recording directory to an email and send it to , where it can be used for diagnosis.