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big "blips" in acquired analog data graphs

I am using the daqpad 6016 to aquire 7 channels of analog voltage data from a device.I am getting large symmetric "star-like" features on my data graphs that appear to be related to my sample rate and are not being produced by my device. I suspect that these are due to some kind of buffering problem but I am not getting any errors from my vi.  I'm using the Daqmx Timing (sample clock).vi and the Daqmx Read. vi with both of the samples per channel connected to a single number (500). I am sampling at 25kHz and averaging over 500 samples at a time giving me an effective rate of 50kHz. Any ideas?
 
Tim
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Attach your vi after removing unnecessary stuff (verify first that the problem is still there, since the problem is often located and solved during this simplification step!..) and somebody will have a look at it.
Chilly Charly    (aka CC)

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How about also posting an example of the plot showing the "star-like" features.

Mike..


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@tvratto wrote:
I am using the daqpad 6016 to aquire 7 channels of analog voltage data from a device.I am getting large symmetric "star-like" features on my data graphs that appear to be related to my sample rate and are not being produced by my device. I suspect that these are due to some kind of buffering problem but I am not getting any errors from my vi.  I'm using the Daqmx Timing (sample clock).vi and the Daqmx Read. vi with both of the samples per channel connected to a single number (500). I am sampling at 25kHz and averaging over 500 samples at a time giving me an effective rate of 50kHz. Any ideas?
Tim

Could it be that some of your 7 channels worth of y-value data is used as an x-value data when you feed it into an XY-graph? That could explain such 'star-shaped' features. Try to use a waveform graph instead of XY graoh then...

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I have attached the vi that is giving me problems.  As I sort of alluded to, the problem appears to be somewhat related to the either the adc rate or the samples/channel selection.

Thanks,

Tim
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Also some plots of the behavior...

Tim
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