DAQmx general question

[Driga]

I am trying to learn the DAQmx. I have an example from a book. It explains about writing a continuous analog waveform.

Then I made another vi by omitting the DAQmx. And the results that I see in the front panel are the same.

It makes me wonder what is the different between them?

I have attached the two vi. 

Thank you.

[RavensFan]

They aren't the same.

DAQmx is the system of drivers you use for interfacing with real hardware.  Your first screenshot shows the creation of a sine wave, its display on the screen, and its output to a DAQ device.  Your second screenshot only shows the creation of the sine wave and its display on the screen.  It has no interface whatsoever to DAQ hardware.

[Dennis_Knutson]

It's really, really simple. In one you are just writing to an indicator - the signal exists only in the memory of your pc. In the other, the DAQmx function will be telling to physically output that signal with a DAQ card. That's what DAQmx is for - configuring a DAQ card to output or acquire some voltage, current, frequency, etc.

[Driga]

Hmm...

Ok.. I need to understand both replies.

One question, in the first picture, why it has not just DAQmx but also the sine wave generator?

And why the data input for the DAQmx write.vi comes from the sine wave generator?

[RavensFan]

You might have a better understanding what LabVIEW is and does if you take the tutorials.

LabVIEW Introduction Course - Three Hours
LabVIEW Introduction Course - Six Hours

Someone wanted to create a VI that as it runs, varies the value shown in a front panel indicator in a sinusoidal pattern.  They could have picked triangular.  They could have picked a random number generator.  They could have let it be decided by a number the user enters into a front panel control.  Or from a dataset that was read in from a text file.  Instead of showing it in a scalar indicator, they could have displayed it on a waveform chart.

In the other VI, they wanted to do the same thing, but also have that value show up as a real world voltage being output through a DAQ card.>

Message Edited by Ravens Fan on 02-27-2010 12:46 AM