LabVIEW Real-Time Quiz Feedback

[jkurtw]

Please reply to this discussion thread with any feedback on the LabVIEW Real-Time Skills Quiz.

[dwisti]

21 out of 24 correct.  This one got me because it says (correct answer) at the end...  but its the wrong answer...

[jkurtw]

Thanks for catching that, David.

We will get it fixed.

Nice job on the quiz!

[Ben_Phillips]

(I don't understand also why I can't add paragraph separators on the NI forums, I've had this problem before.  I paste in a reply, I then ADD line breaks, and still all the paragraphs are jumbled together.)

Quiz feedback:

#6  Really?  You can't use the 1 MHZ timing source on the PXI controller?  Do you really have to use an external clock source?  This seems crazy to me, the PXI clocks are supposed to be the most stable clocks available short of some type of atomic clock.

Using some type of pulse generator to generate pulse clocks is absolutely nutty, I know these exist in the PXI chassis.

This is important to me, I've been timing my realtime clocks on my timed RT loops to the PXI clock.  If this is not deterministic, I don't know what is.

Is this a typo?

"Timed Loops for DAQmx tasks should use the external timing source of the task."

Dude, you should be able to clock the loop/task at the PXI timing rate.  There's a MHZ and KHZ rate available.  No errors are thrown when I use any of the options on timed loops.

If I'm wrong about this, I need to seriously reconsider several things I've done.

Thanks,

-Ben

[ryank]

The main point is that the loop is driven by the event of a DAQmx sample being available.  Therefore, you should synchronize the loop with the scan clock on the DAQ board (which is what they are referring to as an external clock) not because it's a lower-jitter clock (although in some cases it is) but because it's the actual rate you are trying to run the loop.  Using the PXI clock would just introduce an unnecessary second clock into the system, which will drift in relation to the clock you are interested in.