Timer skips upon multichannel acquisition

[KarenM]

Hi,

I am developping a 4-channel acquisition which is read from one device (USB-6210), and would like to record the 4 input signals to a graph, then to file. The signals are acquired at an effective sampling rate of 1S/s (averaging 50 samples at 50Hz).

The files are written based on the output from a function which formats the signal data: this includes a timer counter the data itself, and calculated data in multiple columns. When I run the program, The timer starts off correctly (it is self-programmed) but will eventually go out of sync -- after 10 minutes, the timer will skip by 4. The final data in the file is all present, but just the user interface is not presenting well. I tried to compare the timer with the system time, but when I run the program, the system time will also eventually skip the display to every 4s.

My guess is that this is caused by memory accumulation so I have tried to minimize this - I have used an event structure and already placed all the functions that I could.  The remainder of the processes in the main loop are necessary for processing the data prior to graphing.  

I have tried using parallel loops with the DAQmx task outside of the loop, but this does not work.

I use a lot of local variables, so am going to see if I can reduce this. 

Any thoughts or suggestions? I unfortunately I cannot post my code, thanks!

[BowenM]

With that low of a sample rate, I don't see memory problems happening after 10 minutes.

Can you at least post screenshots of the acquisition portion of your code?  I'm having a hard time visualizing what is going on.

[Norbert_B]

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@BowenM wrote:

[...]Can you at least post screenshots of the acquisition portion of your code? [..]

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Far better would be to post your VI(s) which you are using.

Is my understanding correct that your "timestamp" is "late" for 4s after a period of 10 minutes (600 seconds)? If not, please clearify the exact issue with your timestamp.

Norbert