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Testing the Stability of an External IRIG Source

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    Last Modified: September 15, 2017

    Tests the stability of an external IRIG source relative to an external time reference like GPS or IEEE 1588-2008 using NI-Sync.

    Setting an External Time Reference
    1. Set the external time reference of a time-based timing and synchronization module to the source you want to measure IRIG stability against.
    2. Place Enable GPS or IRIG Timestamping on the diagram.
    3. Select the IRIG mode and set the IRIG Type you would like to measure, either IRIGB AM or IRIGB DC.
    4. Wire the hardware terminal containing the external IRIG source to terminal of Enable GPS or IRIG Timestamping.
    5. Place a While Loop on the block diagram.
    6. Place Read Last GPS or IRIG Timestamp in the While Loop, select the IRIG mode, and wire the following terminals:
      1. Wire the NI-Sync instrument handle to instrument handle.
      2. Wire the terminal containing the external IRIG source to terminal.
      3. Wire indicators to IRIG Time and timestamp.
    7. Place Disable GPS or IRIG Timestamping outside of the While Loop, select the IRIG mode, and wire the relevant terminals.
    8. Place Close on the diagram to end the NI-Sync session.
    On every iteration of the While Loop, the program returns the IRIG-B timestamp and a timestamp of the board time when the module received the IRIG-B message. The difference between these two timestamps is the offset. You can use the offset to help determine if the IRIG-B source is stable enough for your application. Using a While Loop returns multiple timestamps, which allows you to perform a more detailed analysis of the offset.

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