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1MHz noise from embedded pxi controller?

I am using a NI-PXI-8187 embedded controller in a NI-PXI-1045 cardframe.  I am using NI-PXI-6115 cards for data acquisition.  At the input of the 6115 cards, i see a 1MHz spike of about 40mV.  When I remove the computer it's gone.  I also have an older 8176 controller inside a 1000B cardframe, and I see the same noise at about 100mV.  Is this a known problem, and if so is there a soution?
 
Thanks,
 
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Hi mhfracis-
 
When you say you see this spike at the input, do you mean it shows up in the data you acquire in your application or are you probing the inputs with an oscilloscope?  Which computer are you referring to when you say "when I remove the computer it's gone" ?  If you can provide a bit more information about the problem I will be happy to help out.
 
Thanks-
Tom W
National Instruments
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I was probing a signal going into the 6115 input using an oscilloscope, and noticed the spike walking across.  I traced it to the embedded controller, when i shut it down and removed it from the cardframe, the spike did not show up in the signal any more.  I then found another cardframe, embedded controller, and 6115 card.  I did this test again, and found the same spike occurring.  The spike again dissappeared when i removed the embedded controller.
 
Thanks,
 
Matt
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Hi Matt-

When you say you traced the signals to the embedded controller, do you mean that removing the controller removed the problem or that you literally traced the 1MHz signal to some point on the controller.  When you remove the controller are you still running the DAQ card via MXI or some other remote means?  If the system is not operational I would expect to see the noise being induced if it is indeed coming from the system itself.

When you acquire data with the DAQ card do you see similar noise?  A great example to try for LabVIEW would be "Cont Acq&Graph Voltage-Int Clk.vi" from the NI Example Finder (Help>>Find Examples) under Hardware Input and Output>>DAQmx>>Analog Measurements>>Voltage.  Please let me know if the spike shows in the data read by the DAQ card as well.

Thanks-

Tom W
National Instruments
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