Why does waveform AO interfere with DC AO?

[epsilon-delta]

I am using a PXI-6289 and two PXI-6733 to generate AO sine waves and DC voltages.  For waveform generation I am using the sine waveform generation VI to feed a DAQ Assistant node (continuous waveform generation).  I am generating one sinewave from the 6289.  I am also generating two DC output voltages using DAQ Assistant node (one sample on demand).  On one of the 6733's I am using all eight AO outputs to generate DC voltages.  On the other 6733 I am using all AO outputs to generate sine waveforms in the same manner as for the 6289.  For each desired waveform, sine or DC, I have created a VI which uses a DAQ Assistant node as described.  Each VI works fine with no problems, whether it be a DC output or a sine output.  But when I group all of these VI's together in a single VI so I can generate all the signals simultaneously, problems occur.  Right now what I am seeing is that if I keep the sine output channels set at zero, all the DC outputs work just fine.  But as soon as I start increasing one the output of one of the sine wave channels, all the DC outputs dissapear, leaving only the sine outputs.  If I reduce the DC outputs to zero, the DC voltages return.  Does anyone have any insight into what the problem might be?  Thank you.

[Seth_B.]

Hello epsilon-delta,

Without seeing your code, it's difficult to say exactly what the problem is.  Could you post the VI that is showing the problem, along with any SubVIs used?

Thanks,

[epsilon-delta]

Seth,

Thank you for your response.  I cannot send you my code because it is proprietary. 

Perhaps you could give me an example VI that generates three DC voltages (of different amplitudes) from three AO channels of the first PXI-6733 and three sinewaves from three different AO channels of the second PXI-6733 (of different amplitudes and frequencies), all being generated simultaneously.  Let's make the sine frequencies 1000 Hz, 500 Hz, and 100 Hz.  I think that would help me to understand how multiple-board AO is achieved.

epsilon-delta

[Seth_B.]

Hello epsilon-delta,

This is a very rough example, but it shows the basic operation.  For DC values, all you need to do is update the value on the line (See the "Gen Voltage Update.vi" example in the LabVIEW Example Finder).  The rest is based on the "Cont Gen Voltage Wfm - Int Clk.vi"example, showing how to do waveform generation.  The DC portion starts just before the sine wave portion.  If you want them to start at exactly the same time, we'll need to configure a trigger.  Let me know if you have any questions.

Regards,