I have an application that uses a SCXI chassis, with two analog inputs (voltage and thermocouples), both multiplexed 32 channels.
I've used LV express tasks to set up a DAQ sampling system that uses N Samples (target is 10 samples/channel per VI read, but sampling at 1000Hz at the hardward side), and set this up in a timed loop at 100ms timing and high priority. However, I found the loop was running slow and found that it was across the VI task that this was happening, which took anywhere from 500 to 1000ms to complete despite the read timing being 10ms.
I reverted this Express VI to it's component VI and played with some of the parameters in there but couldn't get the speed up save by cutting down the number of samples per read, which is not what I want to do.
I did find that if I used continuous sampling from an Express VI setup, the read speed in the loop was excellent, but I would get 0 values too frequently to be useful for the main application (as there's heating loops to consider)
I did see that there's an Example that continuously reads a single thermocouple channel using the N-sample type approach, but that the biggest difference between this and the expanded Express VI is that the example does NOT include the Sample Clock timing - it just uses the DAQ read to pull values in.
This is with LabView 7.1.1f. I believe I had used the sample approach with the N-sample reads in a previous version (7.0?) with a similar SCXI chassis without a problem of this slow read, so I'm wondering if there's something int he software or drivers that changed between these two.
Would the best way to proceed is to ignore the Express VI (save for the task setup stuff) and use the example approach?
