N samples at constant samplig rate - Ni 9234 and Sound and Vibration

[MaLac]

Hi,

I want to acquire a fixed number of samples using Ni 9234, a compacDaq and Sound and vibration.

I need 131072 samples at 2048Hz. The project is fairly simple. There is just 2 tasks, acquire and write to ascii.

In the acquire config, if I specify 131072 samples, it doesn't work. I suppose it was because it was too large. So I set 8192 samples and I execute the loop 16 times. At first it seems to work, I had the right number of data in my text file. But when I looked more closely, it seems that between each iteration, there is a lag of about 0.25s. I need a constant sampling rate. Is there a way to acquire 131072 samples at 2048Hz in one iteration. It would also be nice if I can see the data in real-time.

Thank you

Matt

[MegaWatts]

Many times, this amount of delay occurs due to initializing and closing the task inside the same loop as your aquisition. Are you doing this in your application? It may be helpful for you to post some more information about how you are setting up your application.

Regards,

Matt Watts

Applications Engineer

National Instruments

www.ni.com/support

[MaLac]

Hi,

My application is quite simple, but since it's done with signal express, I don't quite know what happen in the background.

Here a screenshoot (it's in French)

[MegaWatts]

Hey,

How are you verifying the 0.25s delay?

[MaLac]

Hi,

I logged the data in an ascii file, I should have recorded them also but I forgot. The first column of the ascii file is the relative time. I also observed that there are more digits after the first iteration, you may look at the screenshot of the ascii file below.

I said 0,25s, but it was to illustrate, it's 0,1652s in fact.

Thank you for your support

Matt

[MaLac]

I'm still having the same issue. Does someone found a solution ?

Thank you

Matt