Testing the Stability of an External IRIG Source

Prerequisites: Selecting a Time Reference

You can test the stability of an external IRIG source relative to a selected time reference using NI-Sync. Complete the following steps to build a basic program to judge if the stability of an IRIG source is appropriate for your application:

1. Set the selected time reference of a time-based timing and synchronization module to the time reference you want to measure IRIG stability against.
2. Place niSync Enable GPS or IRIG Timestamping.
3. Select the IRIG instance 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 niSync Enable GPS or IRIG Timestamping.
5. Place a While Loop.
6. Place niSync Read Last GPS or IRIG Timestamp in the While Loop, select the IRIG instance, 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 niSync Disable GPS or IRIG Timestamping outside of the While Loop, select the IRIG instance, and wire the relevant terminals.
8. Place niSync Close 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.