Real-Time Measurement and Control

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Sampling Problem with Flexrio

Hi ,


I have Problem with Flexrio. I get signal parts that do not exist normally. Here is a picture.





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Message 1 of 7

Hi labview_jumper,


I'm assuming that you're use to cRIO or R series since the FPGA code you're showing (right?).

Actually, Analog FlexRIO adaptor Modules have their own clock, so you usually want you're AI node to be inside a SCTL running at the AI Clock rate.


Which module are you using? I'd suggest with give a try to the LabVIEW example associate to that module, that will give the architecture basis you should respect to use your FlexRIO.


Have a good day,

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Message 2 of 7

Hello ,


I am using NI 5752  with 7966R. I am also getting wierd signal shapes even when running their example programs. I can see that gain is varying at different frequencies even without any gain control implementation. What may be the reason for this? Any idea?



Thank you,


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Message 3 of 7

Hello Mittu1,


I dont mind you post on that thread but you might get more answer creating a new one 😉


concerning your issue with the 5752, this make me think about an issue I have faced.

Can you tell us more about the signal you're sampling? The 5752 is design for ultrasound so there is a filter with a 16KHz cutoff frequency.

(see or


So you cannot trust any result you're seeing about the gain if your signal frequency is lower 16KHz.

I hope this help.

Have a great day,

Message 4 of 7

Hi Florent,


No i am working with ultrasound signals. If coming below 100 KhZ signal amplitude is very much high and at higher frequencies above 1 MhZ, it is coming down drastically. Really wierd behaviour. Can you suggest me any way to solve this?My signals are in the range of 200 khz to 6 MhZ. With very low amplitude..Say 10 mvpp.



Thank you,


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Message 5 of 7

Hi Mittun,


did you try to use the 5781 example in which you can configure the ADC? Which anti-aliases filter do you use (7.5MHz, 10MHz or 14MHz)?

That can explain a lot about the amplitude variation you're seen 🙂

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Message 6 of 7

I tested NI 5752 with PXIe-7961R by using ConfigureDAC example.

Input signal is square wave of 500 KHz through SMB-2145.

Output is not square wave but half square half triangle wave.

I attach the photo of output wave.


I don't known how to solve this problem.

Do you know how to solve its? Please tell me if you know.

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Message 7 of 7