High sampling rate is not accurate

Dear alls,
Any one know why the time loop is not accurate at defined period at the RealTime Trace Viewer ? In figure of VI, I set the period for the time loop is 250 us, but when I analyze in Real time Trace Viewer, it shows the real period time about 676 us. That means my data acquisition will be sampled in wrong sampling rate.
Could you give me some explane, please? And how can I solve this problem? I tested this code with MyRIO board.
Best Regards,
Kien 

crossrulz wrote:
Why do you have a wait in your timed loop?  The point of the Timed Loop is to state the loop rate.
 ??? Bigger problems than that!  Why do you have any timing other that the TASK timing? And really, The task timing is most likely the loop rate.
Can you post your actual VI?  I suspect something else is happening here that we cannot see (configurations, channels used, etc).
And a snip of the Task needs posting

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