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U6 DAC pulse output problem

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#1 Kennorcross

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Posted 04 April 2014 - 08:15 AM

I have the U6, and I'm using a slightly modified version of the “U3 DAC Function Geneator.vi” example  to create/control a simple square wave output (either 10Hz @ 20% duty cycle, or  50Hz @ 22%  duty cycle).


At 10 Hz, everything looks fine, but at 50 Hz, the resulting output from the U6 seems a bit unstable – variations in duty cycle and about a +/- 2Hz shift in frequency.


Is this due to the limitations of the U6 itself, or could it be attributed to a timing issue in labVIEW?

Attached Thumbnails

  • Square_wave_generator.jpg
  • 50Hz_22pctDC_test1.jpg
  • 50Hz_22pctDC_test2.jpg

#2 LabJack Support

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Posted 04 April 2014 - 12:14 PM

In your block diagram I can see that you are trying to update the U3 every 2ms.  That is not impossible, but down in the realm of jitter for command-response calls:




The Waveform Generation app note has good info also:



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