Hello everyone,
I am facing a very strange behavior when using timed loop structures. At least, with all the tests I already performed I am still not able to explain what causes it.
- When I am using a timed loop with an absolute time source a huge delay can be observed between the expected start time of each iteration and its actual start time.
However if I use a relative time source instead, this behavior do not appear, thus, the start time and actual time are the same.
To observe this behavior, I built up two similar VIs, both with timed loops (one with an absolute time source and the other with a relative time source), inside the timed loop only the expected and actual time instants are saved into an array, no more actions are performed.
The results are shown below, they show two arrays one with the stored expected time instants and the other with the actual time instants. The time step used in these tests was 10ms. Even with larger time steps the same behavior can be verified (I have tested with 100ms and 1s).
Absolute Time source results:
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As you can notice, with an absolute time source, the delays between the expected time instant and the actual time instants are huge and their values are random. In this test case, with 10ms time steps, the delays observed are huge enough to make some of the timed events to be jumped off.
Relative time source:
(image will be added as soon as possible...)
Here with the relative time source everything worked as I wanted and the expected time and actual time instants are the same!
I am using LabVIEW 2012 SP1. I performed the same test on different company computers (similar machines) and the result was exactly the same. I also try to use LabVIEW 2010 and I observed the same behavior.
Anyone has any idea to explain this strange behavior??
I know my company's computers are a bit old and have a lot of stuff running on background, but if this was the reason for the delay, Why the same delay is not observed with both relative and absolute time sources?
Thank you all.
Regards,