How Do I Configure My 6608 Real-Time Clock for GPS Timing Synchronization?Hardware: Counter/Timers (TIO)>>Devices>>PXI-6608
Problem: I am trying to use my 6608 counter/timer board to synchronize my measurements with a GPS timing signal. The shipping examples make a call to the Clock Program Hardware (NI-TIO).vi, but I cannot figure out what parameters I need to set. How do I make it work?Solution: The Clock Program Hardware (NI-TIO).vi has two inputs that you must configure in order for the GPS synchronization to work properly: Synchronization Method and Initial Clock Time Specification. The 6608 supports two GPS timing signals: Pulse Per Second (PPS) and IRIG-B. The synchronization method you specify here must match the method you specified for the Clock Synchronization (NI-TIO).vi. You can read more information about the different synchronization methods in Developer Zone Tutorial: Synchronizing and Correlating Measurements to a Global Timebase with GPS.If you use the PPS synchronization method, you must specify an initial time for the real-time clock on the 6608. Using the Initial Clock Specification input, you can set the initial time explicitly ("time in seconds"), let the clock use the computer's system time as the initial time ("use system time"), or just let the clock keeps its current value, assuming it was previously synchronized correctly ("use previous clock time"). An IRIG-B signal, on the other hand, contains information about the number of seconds, minutes, hours, and days that have elapsed since the beginning of the current year. The timestamp counter is adjusted automatically to reflect this, and there is no need to program an initial time. Thus, the "Use Previous Clock Time" setting is the only setting that will work when connecting an IRIG-B signal. This is because it is the only option that sets the Initial Seconds Enable attribute of the real-time clock to no. The other two settings may generate erroneous values for your timestamps. Refer to the related links below for more information about how to interface your GPS timing signals. Related Links: Developer Zone Tutorial: Synchronizing and Correlating Measurements to a Global Timebase with GPS KnowledgeBase 3GF8NQW1: PXI-6608 not recognizing IRIG-B signals for GPS time KnowledgeBase 27599UYF: GPS-Based Synchronization on the NI 6608 Attachments:
Report Date: 08/31/2005 Last Updated: 07/26/2007 Document ID: 3OU74CS9 |
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