Leaderboard

I think so. Yes the bottom loop is free-running. Put an indicator on the front panel wired to the difference between 2 "GetTickCount" VIs. You will see that it is pretty much "0". You are in fact putting all the data onto 1 un-named queue. So, every 3 ms you are adding 4 lots of data, but you don't know which order the bottom de-queues execute in or, indeed, which order they were originally placed (but that's another issue). Your time-out is is exactly the same (3 ms) so if there are 4 pieces of data on the queue, then everything is fine. However this is unlikely since the producer and consumer are not synchronised. If a timeout occurs; you still increment your counter so, due to jitter, sometimes you are reading data, and sometimes you are just timing out.....but.... you still only display the data (and add it to the history) in case 19. And although you will read it next time around, you don't know on which graph it will be. You have a race condition between data arriving and timing out. Does that make sense?