I know this post is old, but I may as well contribute. I'm not sure of your but there's a different approach you could try. The "DAQmx Is Task Done" VI I've seen it mostly in AO (analog output) operations, and for the looks of things, you're doing AI (analog input). Even though 200 ms seems a fairly long time for querying / software re-arming, I'd advise you to use a Pause trigger, taking into account your X Series can handle analog triggering (not sure if that's the case, but it can also handle digital triggering, as well).