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Member
CHersh
Posts: 5
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SignalExpress freezing at stop of log, USB6008

Hi everyone,

 

I am wanting to use my NI USB-6008 DAQ to take a voltage data point on four channels once every 10 minutes for a few days at a time.  I have changed the timeout to -1 seconds and turned off automatic exporting of log file.  I am also using the save to ASCII step.  When I go to stop the run, it hangs up.  My computer is pretty bad, but I can do the same operation with a much faster sample rate no problem.  Does the 6008 have a lower limit to sampling rate?  I just started messing with this program yesterday so I'm still learning.

 

Thanks,

Chris

Member
CHersh
Posts: 5
0 Kudos

Re: SignalExpress freezing at stop of log, USB6008

I tried using my laptop (which is much faster than the desktop I'm using) and I got the same problem.  Any suggestions?

Member
CHersh
Posts: 5
0 Kudos

Re: SignalExpress freezing at stop of log, USB6008

So I did some more searching through the expansive knowledge base and found that the minimum sample rate for the USB 6008 is 5.587935 mHz (source).  

 

I ditched the save to ASCII step for now, and have gotten the program to collect some data at 10 mHz, currently trying it at 6 mHz now.  

 

The main cause to my problem so far has been with what seems to be an error with the continuous data collection option.  I discovered that eventhough the sample size is supposed to be treated as buffer size in this mode, for me it was not.  I would set it to 20k 'buffer' at something like 1 kHz samples and it would 'freeze' on stop.  I let it go like this for a while once and to my suprise it came out of it and I was able to view the log.  When I did I saw that the log went to exactly 20k samples, eventhough I had stopped it within ~5 seconds.  So during that time it was 'stopping' it was actually finishing the program and getting 20k samples.  This is why I always had a problem trying to record at low sample rates with what I thought was a 1k buffer - but was actually 1k samples. 

 

So..... why is this happening?  I want to actually collect continuously, but also stop it whenver I want (eg. continuous up until I stop it).  I might try the 'n-sample' mode now, considering the rest of the problems with this program, they could very well be flipped. 

 

Assuming I figure out how to get it into true continous mode, will I be able to stop the logging at my will?  And what should I set the buffer to with a sample rate of 6 mHz?

 

 

Thanks,

Chris

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