Continuous acquisition with time variation

[pbsalunkhe]

I am working on Labview 7.1, Windows xp. The NI card is 6040E series card.

I am acquiring the data from DAQ Assistant with sampling rate of 20 kHz and 5000 number of samples.

The total data acquisition time for 5000 samples will be 0.25 sec (5000/20,000=0.25).

My problem is that, when I acquire the data for say 3 mins. then the x axis scale i.e time should vary from 0 to

180 sec. But it is remaining from 0 to 0.25 sec. However I am getting the desired waveform. I want the time should vary continuously as long as I am acquiring the data. I am attaching herewith the screenshot of waveform with time scale from 0 to 0.25 sec.

Thanks in advance for your help.

Pramod

[Speedy_Badger]

Hello Pramod,

Are you using a graph or a chart to display your data when acquiring with the DAQ assistant? Also, are you using finite or continuous acquisition?

If you are using a graph to display your information, this behavior is to be expected. The graph displays whatever data is given to it at any point in time. So when you acquire at 5000 samples at 20KHz, it will display these individual chunks as they are read from the 6040E.

You have two options to get around this. The first is to use a chart instead of a graph, and the second is to concatenate your data and use shift registers so that you retain previous chunks of data. I have included an example VI which displays information in a traditional graph, a chart, and also a modified graph for comparison.

I hope this helps and let me know if I can clarify anything else.

Regards,

[pbsalunkhe]

Thank you very much Chris for your help.

Earlier I was using graph to see the waveform.

pramod