I was in a another recent thread dealing with this term "sampling rate (aggregate)". I explained it by saying that it defined the maximum rate of A/D *conversions*.
What makes for some confusion is that DAQmx uses some different terminology and conventions. DAQmx doesn't give you access to individual conversions, it only gives you access to *samples*. Under DAQmx, 1 "sample" ALWAYS means 1 A/D conversion for each channel in the task. A task with 5 channels on a board with a 250 kHz max *aggregate* rate, would have a *sample rate* of 50 kHz.
When you read data using DAQmx, it will always be returned in units of samples which will include 1 A/D conversion for each channel in the task. You cannot retrieve only the A/D conversions for the 3rd channel out of 5.
-Kevin P
CAUTION! New LabVIEW adopters -- it's too late for me, but you *can* save yourself. The new subscription policy for LabVIEW puts NI's hand in your wallet for the rest of your working life. Are you sure you're *that* dedicated to LabVIEW? (Summary of my reasons in this post, part of a voluminous thread of mostly complaints starting here).