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Question on the impulse noise during the data acquisition.

Hello,

 

I am doing the data acquisition using the NI-5781 adapter module and PXIe-7966R FPGA. However, the sampled signal has a lot of impulse noise and I cannot figure out the exact reason of it. I have tried an example program in LabVIEW and the waveform has no impulse noise, so I think there is no issue with the hardware. The NI 5781 - Getting Started (Host) is the example program. I suspect that the main difference is the streaming function shown below. However, I do not understand what the stream index refers to. In the example, the index is set as 0. But there is always an error when I set the index in my own program. Could someone tell me the exact reason of the noise and helps to solve the problem for me? Thanks a lot!

XunZou_1-1649868994365.png

 

XunZou_0-1649868505158.png

 

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Message 1 of 5
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Well this first thing I would to would be to find out if the noise is real or not with an oscilloscope.

 

If the noise is real then you have two options. 

  1. Hardware noise filtering. (capacitor, ferrites, etc.)
  2. Software noise filtering. (lowpass filter, integration, etc.)

If the noise is not real then you have some other problem going on...

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=== Engineer Ambiguously ===
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Hello,

 

Thanks for your reply. I do not know what the real noise means. But the sine signal has no spike when I test it with the oscilloscope. I have tried to use the median filters, as shown in my attached VI, to reduce the effect of noise. It does improve the signal quality but the noise cannot be completely eliminated.

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@XunZou wrote:

Hello,

 

Thanks for your reply. I do not know what the real noise means. But the sine signal has no spike when I test it with the oscilloscope. I have tried to use the median filters, as shown in my attached VI, to reduce the effect of noise. It does improve the signal quality but the noise cannot be completely eliminated.


Real as in the noise is coming from circuit or device you are testing, but you said you don't see is with an oscilloscope so it's not real in tha sense.

 

That means it's some kind of artifact or noise in your DAQ. I have never used NI-5781 or PXIe-7966R FPGA so I am out of ideas.

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=== Engineer Ambiguously ===
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No worries. Thanks for your help anyway.

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