Embedded Data Logger

NI VeriStand 2018 Help

Edition Date: May 2018

Part Number: 372846M-01

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The NI VeriStand Embedded Data Logger is a custom device that allows you to log data on a target, as opposed to logging data on the host. With this custom device, you can perform the following actions:

  • Log channel data to one or more TDMS log files
  • Organize your TDMS log files by logging channels in channel groups
  • Add metadata to your TDMS log files, such as a description and the unit of a channel
  • Close, open, and start new TDMS log files programmatically
  • Configure triggers to start and stop logging

Because the Embedded Data Logger logs data on the target, you should use it when you need to log more data than the bandwidth of the connection between the target or targets and the host allows. For example, to log data on several RT targets, you can use the Embedded Data Logger, rather than streaming the data from each target back to the host.

The Embedded Data Logger also allows you to log data after you disconnect the host machine. This is useful, for example, if you want to deploy your system definition to an RT target, disconnect your host computer, and let the target run over a weekend.

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Configuring the Embedded Data Logger

Components of the Embedded Data Logger

The following image shows an example Embedded Data Logger in the System Explorer window configuration tree.

The following list explains each of the various components of the Embedded Data Logger:

  • Embedded Data Logger—Use the Embedded Data Logger configuration page to configure the basic settings of the Embedded Data Logger, such as its name and FIFO depth, and to add log files to the Embedded Data Logger.
    • FIFO Utilization—This channel outputs the percentage of the Data FIFO currently in use by the Embedded Data Logger. If the percentage reaches 100%, you could lose data. To avoid data loss, increase the FIFO depth value on the Embedded Data Logger configuration page.
    • Log File—Use the configuration page for Log File to specify general settings for your log file, such as its name and the directory to which to save the file.
      • Channel Groups—This node contains the channel groups you add to your log file. Use the Channel Groups configuration page to add and manage the channel groups for your log files.
        • Channel Group—Use the configuration page for Channel Group to specify the settings of that channel group, such as the name and decimation, as well as to add channels to log to the channel group.
      • Commands—This node contains channels you can use to send commands to the Embedded Data Logger.
        • Log Command—Controls the data logging operation. Use this channel to programmatically open or close data log files. For more information about using the Log Command channel, see its configuration page.
        • Log Trigger—Controls whether the Embedded Data Logger logs data to the log file. Use this channel to programmatically start and stop logging. For example, say you are running an engine simulation and want to start logging when the engine temperature exceeds a certain degree. You can create a procedure that sends a command to start logging when your engine temperature channel exceeds that value.
      • Status—This node contains channels that output important status information about the Embedded Data Logger.
        • File Status—Indicates whether the current log file is opened or closed.
        • Missed Packets—Indicates the total number of packets lost for the data log file.
        • TDMS Error Code—Indicates the error code value for the last reported TDMS file operation error.

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