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Labview 7.1 and DAQmx 7.2 used with 6035E card sort of hangs when doing data acquisition

Hi.

I have a low cost 6035E card installed on quite a fast computer(2.4Ghz, 1GB RAM).Now I wrote a small application to acquire data from 4 channels when a triggering event occurs. All the 4 channels have been configured to sample at 50KS/s each. I understand that the maximum sampling rate of the DAQ card is 200KS/s(hence 200KS/s / 4=50Ks/s).Now I wanted to continuously acquire 10 seconds of data when an event occurs. So I programmed the vi such that acquistion starts at the rising edge and stops at the falling edge of a digital trgger.The number of pretrigger samples was set to 499998(50KS/s x 10 seconds- 2 posttrigger samples).

And I wanted to save the data during this 10 seconds so I used the write LVM express VI.

Now this VI seems to work very sluggishly.

I cant stop the application using the stop button. It takes like about 5 min and then it stops.

Also I notice that no data was written to the LVM file. It creates a LVM file each time I run this but the size of the file is 0KB.

What is happening here?

If I decrease the acquistion time,say for 1 second and set the triggers accordingly with the number of pretrigger samples set to 49998, the vi seems to work fine and data is saved to the file correctly.I am pretty sure my triggering bit is working well.

Any suggestions?
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<>>

my guess is that you are generating huge amount of data (as you said), and you are using the LVM express vi. each time it is called it opens the file, write data to it, then closes it. Once the file size becomes big enough, things will slow down, I have seen it and there has been several threads about it.
Instead of using the LVM vi , open the file first time you access it, then write data to it and do not close it. Next time you write data to it (it is already open, just write to it(appened option).

After data Acq is finished, write data for the last time, then close the file.

(look at a LV example of streaming data to disk.)
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I might also suggest an update to your DAQmx. DAQmx 7.4 (downloadable from the NI site) has as much as a 60% faster acquisition rate over DAQmx 7.3 (and you're using 7.2). We solved a number of DAQ related problems when we updated our DAQmx (not all, but most problems).

Rob
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