to run more than one DAQmx AO task at the same time

[JohnS11]

Is there any reason cannot run more than one DAQmx AO task at the same time?

[DianeS]

That depends.

If you're doing single-point, software-timed output (i.e. 1Chan 1Samp or NChan 1Samp), then you should be able to run multiple AO tasks.

If you're doing hardware-timed output (i.e. 1Chan NSamp or NChan NSamp), using a card which has only one AO sample clock, then you cannot run multiple AO tasks.  All of your output channels must be in a single task.

If you're doing hardware-timed output using a card with multiple AO sample clocks, then you can run as many AO tasks as there are AO sample clocks.

Does that answer your question?  I might be able to help further if I knew what it was you actually want to do.

[JohnS11]

Dear Diane,

Thanks for the help. I'm new to labview. For the pci 6221, I haved used up the two counters for encoder reading.

1)How many AO sample clock for the M series card (pci 6221 and pci 6259)? one correct for each card, correct?

2) If I haved used up the two counters for encoder reading, can I still use the hardware time using sample clock?

3) I dont quite understand about AO sample clock? Is is the sama as AI sample clock?

4) Whats the relationship between clock and counter?

5) Can you explain what does it means by single point?

6) How to calculate the software time? can share example u have?

I want to analog output two voltage

[JohnS11]

7) How to define the sampling rate? whats the rule of thumb?

[Dennis_Knutson]

Those cards have a single AO clock each. They each have a single AI clock that is separate. Using hardware timed I/O means you cannot have separate tasks for a specific resource (i.e. AO). Single point or on demand sampling is strictly software timed and is highly variable with a great deal of jitter on non-deterministic operating systems. So, use both channels in a single task.

[smercurio_fc · Accepted solution]

That's a lot of questions you listed there. I would strongly suggest that you spend some time reviewing the numerous tutorials available for data acquisition here: http://www.ni.com/white-paper/5434/en. You will need to get a better understanding of how the equipment works, and reading some of those articles will help you considerably.