Beginner Q: timebase signal and clock

Question

What is the internal clock of DAQ MIO-16EX-50? Does it mean when you don't define your own clock, it will use the internal clcok to sample data? What is the rate of this internal clock?
I am contuing other people's Labview DAQ program. he used external clock, but not the same as the Labview example, he used "clock config vi", set clcok to "0", then input his clock source and alternate clock rate specification. I ask why he did this, why he didn't use PFI7/startscan to input his external clcok. He said because this is the timebased signal. I don't understand. What is the difference when you use PFI7/startscan as external clock (like the example of Cont Acq&Graph ExtScanClk.vi) and his program. Can anyone give me some idea?

Answer 1

May,
The DAQ device has two available internal timebases, 20 MHz and 100 kHz. When an internal scan clock (STARTSCAN) is used, the actual clock is derived by dividing-down one of these timebases. An external scan clock can also be provided (for example, from PFI 7). Additionally, an external scan clock timebase (SISOURCE) can be provided to derive the scan clock. The following KnowledgeBase discusses the use of an external timebase in greater detail:
How Do I Use SISOURCE as the External Timebase for the STARTSCAN Signal?
So, the difference between the two programs you have referenced is that one uses an external scan clock and the other u
ses an external scan clock timebase.
Good luck with your application.
Spencer S.