How to record mass-locking and unlocking operations

If you suspect problems with mass-locking and unlocking, Guralp 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.

  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:


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


  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 appears in Scream’s main window, if it is not there already.
  7. Right-click on the digitiser icon and select “Configure”:


  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 “Cancel”
    • If they are clear (not ticked): tick them, click “Upload” and wait for the digitiser to reboot.


  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. 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".


  10. Right-click on the digitiser icon and select “Control”:


  11. Go to the “Mass Control” tab.
  12. Click the “Unlock now” button:


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

  13. If you are having problems with mass centring, click the “Centre now” button and note the time:


    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.

  14. Click the “Lock now” button:


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

  15. Gently tap the side of the instrument with your finger-tip.
  16. Wait twenty minutes:  this is necessary because mass position channels at one sample per second can take over sixteen minutes to assemble enough samples to fill a packet.
  17. Right-click on the digitiser icon and select “Terminal”:


    A terminal window should open.

  18. Key ENTER a few times to get the digitiser’s attention, then enter the command FLUSH-STATUS
  19. Enter the command GO – the terminal window should close:


  20. In Scream’s main window, click the word “Rec” in the column header for stream recording.
  21. Scream will prompt you “Stop recording on all streams?”:


    Click “Yes”: this flushes all outstanding recording buffers to disk.

  22. View the files in the recording directory to check that they are all present (at least three velocity channels, 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”:


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


  23. If you have recorded at least 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 This email address is being protected from spambots. You need JavaScript enabled to view it. , where it can be used for diagnosis.

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