Is the PXI-6723 capable of running multiple AO tasks at the same time

[A Wooten]

Is the PXI-6723 card capable of running multiple AO tasks at the same time?

I have worked with some E-Series Analog cards ( 6040, 6115 ) and have discovered that I can only run one AO task at a time, otherwise I receive a "Resource is reserved" error.

Does this limitation also exists with the 6723?

I need to have independent control of all 32 analog outputs so that I can.

• Trigger each channel independently
• If they are in a single task, they all trigger off of the fist channel in the task
• Control each output independently
• I do not want to have to write a vector containing the data for all 32 channels just to update one channel.
• Also, would this cause glitches in the output?
• I would like to write DC values to a couple of channels, and then a waveform to another channel without updating the DC channels to contain the same number of samples as the waveform data vector.  ( which I would have to do with a single task ).

If the 6723 is not capable of running multiple tasks at the same time, then are then any suggestion on how to achieve the requirements listed above using a single task?

Thanks,

Anson

[mallorim]

Hi Anson,

The PXI-6723 card is not capable of running multiple AO tasks at the same time since a task reserves the timing engine.  The Knowledge Base Document 3STFMI46: Simultaneous Analog Output Tasks on the Same Device discusses the Analog Output task capabilities of National Instruments’ DAQ boards. It is important to note the addendum at the bottom that indicates that the 672x devices are incapable of running both hardware and software timed outputs.

Since you will only be able to use all 32 channels in one task, triggering individual channels will not be possible. The entire task will start at once. You will also need to create an array for all the channels when you want to update any of your outputs, as you suspected.

I hope I answered all your questions. Happy Holidays, Mallori M.

[A Wooten]

Mallori,

Thanks for the reply.

I have some follow up questions.

The addendum to the knowledge base states that  672x devices are incapable of running both hardware and software timed outputs, and can only run one hardware timed analog output at a time.

Are 672x devices ( and other DAQ devices for that matter ) capable of running multiple software timed outputs (no hardware timing)?

Also,  are there any disadvantages to using software timing?

Thanks,

Anson

[mallorim]

Hi Anson,

While I was unable to obtain a 672x device to test, I ran the LabVIEW program in the attached screenshot on a M-Series PCI-6251. The program runs two analog output software-timed tasks, where one channel outputs a repeating array of voltage values and the other channel outputs a constant voltage. I was able to run this program without any errors, indicating that at least an M-series DAQ device is capable of running multiple software timed outputs without any hardware timing.

With regards to your PXI-6723, my best advice would be to test if the card could do this by creating a quick sample program or modifying a previous example and then running it. Make sure that no errors occur during the program. If you have a Scope available or another DAQ card you can use for analog input, you can monitor the 6723’s output. I just connected the output channels of my M-series card to the input channels and viewed a test panel in MAX to see the waveforms.

For a discussion of the differences between hardware timing and software timing, you can see the page 39 or Section 3-4 “Hardware-Timed Generations” of the Analog Output Series User Manual. But basically, hardware timing lets samples be generated faster. Also, software timing is not as accurate as hardware timing with regards to time between samples and software timing is Operating System dependent.

I hope this answers your questions. Happy Holidays, Mallori M.