Wrong duty cycle (pci 6014 and bnc2110)

Hello,
I want to generate a square signal with labview 7.0, pci 6014 and bnc 2110. I attached my VI . The duty cycle works properly for instance for 10%, 20%, 30% (I suppose that it works because when I anlyse the signal: some pulse seams to not appear ) . BUT when I change the duty cycle constant to 15%: the output is again 20% and not 15%. It's the same case for 17%, 18%....
I really need to create square signal with a perfect duty cycle.
Do you know where is the problem?
Thank you
labview 7.0
Attachments:
Untitled41.vi ‏310 KB

I found the problem for missing pulse: it's the while loop. I delete it and add more samples.
The duty cycle works now due to the precision of the "simulate signal"
labview 7.0

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Attachments:
Duty_Cycle.JPG ‏91 KB

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Hey,
I would answer this ...
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Wrong duty cycle (pci 6014 and bnc2110)

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