DAQmx function generator - multiple channel output

[Sanjeevs]

Hello,

               Attached here is my modified version of the code you suggested.  It writes to two outputs now. 

But I see that the output sine signals from the 9263 module  are clean only if the input frequency is a multiple of 10. For other frequencies, it is distorted.

At times, even with the input frequency being a multiple of 10, the output shows some random distortions. 

Is it because of sampling speed/ buffer size problems?

I noticed that the two signal generators are generating perfect sine waves. Distortion occurs only at the output of the 9263 module. 

[CharlesD]

Hello,

First off I suggest gettnig rid of all of your local variables.  Creating controls then creating local variables off of them is very redudant and can actually induce errors later on if the program gets larger.  Please see attached screenshot to see how to properly use Controls.  

Second I suggest opening up the DAQ assistant and placing a check mark in the  "use waveform Timing" check box.  This forces the DAQ assistant and therefore the hardware to use the timing parameters of the waveforms.  Also pleae ensure that the timing parameters in both waveforms express vis are identical.  It is possible that if you specify different timing parameters between the DAQ assistant and the Create signal Express vis that you will see some jitter/ distortions.  See the 2nd screenshot for more information on this.

If this does not resolve your issue pleasetake a screen shot of what you are seeing, and i will go and grab a 92623 and a cdaq chassis and try to reproduce this on my end. 

Thank you 

[Sanjeevs]

Hi 

    I did exactly what you suggested.  I removed the local variables and created controls instead. I also put a checkmark on 'use waveform timing'

Some notes here: 

(1) By setting 'Reset signal' (which is an input to 'Simulate signal' )  to false, I could get rid of the large distortions that used to occur when the frequency was not a multiple of 10.

(2) However, smaller distortions occur unpredictably all the time, even after checking 'use waveform timing' .  (See attached pic 'distorted waveforms.jpg' )

     These distortions are not easy to spot on an Oscilloscope.  I acquired the signals generated from this 9263 module using a 9215 module, and plotted the acquired data in some engineering software.

     The distortions are quite apparent from the attached picture.

I am also attaching a screenshot of my 'Simulate Signal' dialog box here (it looks the same for both signal simulators).    

As you indicated, can you run the code on a 9263 module mounted on cDAQ 9172?   

[CharlesD]

Are these distortion occuring randomly or is it just when you change one of those parameters of the waveform?

The way this program is made, there is nothing to account for the difference in time that it takes to build the waveform in the Express VI.  Therefore anytime you change the frequecy/amplitude/offset etc.. of the waveform there is "Gap" in the information between the old waveform and the new waveform.  This "gap" in information is represented by the gap or discontinuity that you are seeing. Also this gap in information could very well be caused by the difference in the two waveforms.  If they are not complelty meshed together or the frequenc/amplitude change does not match up you will see this distortionwill be see as a discontinuity in the waveform. 

[Sanjeevs]

Thanks. Can you suggest a modification to the code to ensure proper timing? 

[Tim_W]

About 9 years after this dialog, people like myself are still repeating the benefits.  Thanks to both of you for this thread.  Solved my problem in a few minutes, after wasting an entire day floundering on my own.

[ashwini11]

Hello sir,

I am using my daq to perform analog modulation technique. I have to give both carrier and message signal from daq at a time. how to code this?. I used arbitrary waveform generator and function generator from launcher. this works perfectly. But i would like to control the signals generated through labview frontpanel. I got stuck here. could you please help me.?

 Actually i tried to generate the using 2 signals simultaneously. i have attached both the code and obtained results below. please have a look at it