Determining if an AO physical channel is finished outputting on a PCI 6221

[DanJS]

To whom it may concern:

I am using an NI-PCI 6221 with Labview 8.0  Currently, I load a waveform onto the boards buffer and then trigger it to output using a separate channel.  The waveform outputs correctly, but once it stops, the output of the board will not always be zero.  Rather, it will be at the last value of the board's output.  To solve this, I have added a second write.vi to put 0's to the buffer once I retrigger.  However, there is always a slight delay between when the output finishes and wen the second write is implemented.  So, I was wondering how I can determine with the output has finished?  I tried using the "Is task done?" vi but it never goes true, even when the waveform is finished. 

Thanks for any help.

[CharlesD]

Hey DanJS,

Well first off your correct, on Analog outputs the final output after a given operation will not be zero, but the last data point that was written. You are doing the right thing by re-writing a 'ZERO' to the channel.  To basically set the channel back to zero voltage.  Can you expand on how you are configuring your task?  Are you writing continuously?  Finite samples? Because if you are writing the data only once (Finite samples) than you could easily have the last sample in your buffer be a zero and therefore it would always set the last point as zero after the task is complete.   Could you expand a little more on how you are programming your application, maybe attach a screenshot of your code where you writing the data.  This will help us understand better and enable us to provide a better solution.