The diagram shows the interconnections between the two PCI boards that are installed with the SB-Logger analog interface. Note the correspondence of the National Instrument channel numbers and their function in SB-Logger.
The trigger to the external source is connected via a BNC 'T' piece in either of the trigger cables.
In this configuration SB-Logger can acquire up 2 synchronous channels of analog data. The two trigger outputs from the PCI 6601 board are applied to both Analog channels, and each can be enabled or disabled from within the SB-Logger analog server. Future developments may implement more flexibility in the this configuration, for the moment the second trigger output should be regarded as a back-up.
NOTE: the Analog server is a licensed module of SB-Logger, if you do not have a license for the analog server the following dialogs will not be available. Also you must have the National Instruments hardware and drivers installed, an error will be generated if they are not present in the system. See the Hardware installation instructions for details.
After launching SB-Logger click on the red record button:
And then select Triton Analog:
The Server launches
The annotation for each indicator refers to the National Instruments Channel Number (see the diagram)
Hit the configure button
This is the default setup, using trigger 1 and channel 1 only, the Recording Length is 250 Milliseconds and the Sample Frequency is 10,000Hz (10Khz).
Recording Delay may be set to remove the water column from the data, but make sure that the delay is not set to value that will blank out the seabed in shallower parts of the survey area.
Very few Sub Bottom Profilers have transmit frequencies that require a higher Sample Frequency than 10Khz, typically this value needs to be at least twice the highest frequency that is present in the source frequency spectrum. Setting a high frequency here will make the logged files very large, if this value is set very high and the record length is long you may exceed the logging capabilities of the system.
To change the trigger interval click Configure triggers
Enter a value for the shooting rate in Milliseconds.
NOTE: You must choose a shooting interval that is longer than the Recording Length, if you do not SB-Logger will "trim" the record length and you will lose a part of each recorded trace.
Always
check that a short sample file has been been recorded properly by playing it
back BEFORE proceeding with the survey!
To connect to the sonar and start triggering click the sonar On button:
If the default setup is used with Ch1 and Trigger 1 selected then the server display will appear like this when the Sonar On button is clicked:
Indicating that a trigger has been detected on NI Ch0 (trigger 1) and that NI Ch1 (Analog Channel 1) is active. Note there is no detection of the actual trigger on the PCI 6601 board SB-L only monitors the 4 Connectors on the PCI 4474 board.
If the sonar is configured like this and two channels of data will logged in the SEGY file:
Then the indicators will appear thus:
Using the other trigger channel:
The display is like this:
The data channel must ALWAYS include Ch1:
Ch1 only or Ch 1 + Ch 2 do NOT select Ch2 only; this configuration is not supported.
In some cases the sonar may provide the trigger, if this is the case you should select Slave:
Connect the external trigger to Ch0 (Trig 1 input) on the NI PCI 4474 board, note that the pulse must be a TTL compatible pulse with a duration of at least 1mS.
The indicators are the same as for an internal pulse on Ch0:
The PCI 6601 and the PCI 4474 boards are synchronized via the "RTSI" ribbon cable. This setup means that when the master trigger is used, the leading edge of the trigger pulse always occurs at the leading edge of a clock pulse, this arrangement eliminates "sample jitter" which can be evident in very high resolution sub bottom data.
When the trigger is external then the clock is not synched and some sample jitter may be evident.
Refer to the Gain Settings section in Recording Data for help with setting the display gain. Note that these settings have no effect on the signal levels logged in the SEGY file, SB-Logger always logs as raw signal values.