Weird Signal produced by Square wave input( NI-5762, NI-7966R)

[jarrisonwins]

Hello,

We are using a 5762 digitizer attached to a NI 7966R FPGA system. When analyzing signals using the Example LabVIEW Project we are witnessing a strange signal when we look at a square wave input. The top of the square wave almost seems to have an exponential decay, much like you see in RC circuits. We are wondering what is producing this signal and if you guys had any ideas on how to fix it.

[David-A]

Can you post some screenshots of the results you are seeing? Have you done any troubleshooting with the signal source or cabling that led you to the 5762 as the source of the issue? 

[jarrisonwins]

I have attached an image of the appearance of a 1.0 MHz , 1.0 Vpp Square wave. The waveform looks as expected when viewing it with an oscilloscope with the same cables. I believe that the 5762 is the source of these issues.

[David-A]

The image you posted suggests that the the DC portion of the square wave is being attentuated by the AC coupled adapter. Even though the square wave has a frequency of 1MHz the AC coupling is attentuating the low frequency portion of the signal. If you need to eliminate this attenuation you will need to use a different adapter module.

http://www.ni.com/white-paper/14753/en/