Increased response speed for continuous DAQmx with AI and AO

[Paul_C.]

Hi Vincent,

I've gone ahead and posted some information to your other forum thread found here.  I'd like to keep your questions regarding this issue to that thread to help keep our forums easy for future customers to search.  My customer Jenna is actually using her analog input as feedback to determine and change an analog output.  From your other thread, it looks like your just looking for all three to be synchronized. 

I hope this helps,
Paul C.

[WildCherry]

Dear Paul or anybody else who may help!

I have a USB-6211 DAQ and Labview 8.5, and NIDAQmx version 8.71 (the latest one?), running on windows XP

The attached VI exits after about 4 seconds of execution with the overflow error: Error -200279 occurred at DAQmx Read (Analog 1D Wfm NChan NSamp).vi:1

The example is very simple, involving a single loop containing a single channel AI (continuous sampling at 40 samples at rate of 4000 samples/sec), in parralel with a single channel AO, writing a DC value at 10 samples at 1000 samples/sec.

Thus, both read and write should take about 100 mSec per iteration- still the AI buffer gets overflow after just 4 seconds. It is the same phenomenon even if i lower the AO write samples (from 10 to 5 for example)

Could the problem arise from the use of the DAQ assistants instead of the more primitive read/write functions? Shouldn't this also work with the DAQ assistants?

Any help would be greatly appreciated!

PS the problem persists when i changed the AO write rate to 4000 to equal the AI rate

PPS the problem disappears if i disconnect the wire between the simulate signal and the AO daq assistant - meaning the problem resides in the daq assistant or its workings