Are 2 DAC channels faster in 2 tasks than in 1 task?

[Vasilich2004]

I will use NI PCIe-6361 to generate 2 waveforms (2 DACs) and measure 1 signal (ADC).

I need to get max peformance from the card. I have 2 questions:

1. I can use 2 DAC channels in 2 ways

- one task as "Analog 2D DBL NChan NSamp" 

- two tasks as "Analog 1D DBL 1Chan NSamp"

Will "2 tasks" way be faster? Or will " 1 task" use 2 DMA channels and performace will be the same?

I assume data type (waveform. double, int) doesnt influence on performace.

2. DACs and ADC channels will work on the highest rates (> 1 MSamples/s) and ADC and DAC waveforms can be more than 32 (or 64 - don't remember) kB channel memory of NI PCIe-6361 card.

Computer will not do almost anything at that time. Will it work?

[Dennis_Knutson]

The question is moot because you simply cannot have two different tasks.

[Vasilich2004]

What???

As minimum, I was able to create and clear Dev1/ao0 and Dev1/a01 tasks without errros

Maybe it is not possible to create 2 tasks for ADC. But that is different story because there is one resourse - one ADC with multiplexer!

[Dennis_Knutson]

Since you are new to data acquisition and LabVIEW, I would suggest you review some of the tutorials. This has been discussed numerous times. If you want two channels being generated at the same time, you MUST use a single task with all channels. It does not matter whether it is ADC or DAC. Both use a multiplexer with a single convert clock.

[Vasilich2004]

nice answer! typical NI style! In Russian there is proverb for such answer - "одна баба сказала" 😉

1. if you (Dennis_knutson) is correct about DAC then DAQmx has a bug

2. engineer's answer would be : point to place in card or X Series specification or manual Tutorial is secondary document. By the way when Ni website http://sine.ni.com/nips/cds/view/p/lang/en/nid/207411 doesn't show any link to tutorials.

3. by the way, I am 30 years in this bisiness. I use NI cars and LabVIEW as well as other tools. I hope you understand that you are incorrect.

unfortunately, it is very rare when NI provides good and knowledge support.

[crossrulz]

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@Vasilich2004 wrote:

nice answer! typical NI style! In Russian there is proverb for such answer - "одна баба сказала" 😉

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Dennis does not work for NI.  So you can't pin that on NI.  I don't work for NI either.  Most of us on these forums do so for the sake of helping people.  I will admit that Dennis does seem to come off hard on people though.

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Vasilich2004 wrote:

1. if you (Dennis_knutson) is correct about DAC then DAQmx has a bug

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How is that a bug?  The sample clock is a shared resource.  You cannot have two different tasks use the same resource.  Therefore you will need to have all of your analog output channels in the same task.  This is by design.

[Vasilich2004]

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@crossrulz wrote:

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@Vasilich2004 wrote:

nice answer! typical NI style! In Russian there is proverb for such answer - "одна баба сказала" 😉

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Dennis does not work for NI.  So you can't pin that on NI.  I don't work for NI either.  Most of us on these forums do so for the sake of helping people.  I will admit that Dennis does seem to come off hard on people though.

Be precise!

Did I write that Dennis works for NI? No!

I wrote about NI style! Ask to translate - "с кем поведешься от того и наведешься"

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Vasilich2004 wrote:

1. if you (Dennis_knutson) is correct about DAC then DAQmx has a bug

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How is that a bug?  The sample clock is a shared resource.  You cannot have two different tasks use the same resource.  Therefore you will need to have all of your analog output channels in the same task.  This is by design.

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Yes, it is not a bug because 2 tasks can generate waveforms at different time. I mean DAQmx couldn't catch this issue until program will try to start 2 waveform generations simultaniously.

In anyhow, such approach (undescribed limitation in specification) is not good for developers.

[Dennis_Knutson]

The single clock is explained in the manual. Since you have not read it, I wrongly assumed you were a completely new user.