NI 9234 voltage input

[lester14]

Hi all,

I am using NI9234 to collect a rectangular wave generated by function generator. It is a voltage signal. The results I got were always have ripples around the corners of the signal, but not exact straight line. Why is that? I have tried for different sampling frequencies, and coupling type (AC or DC), the results were the same. I also tried oscilloscope to verified the data, it can get the correct signal which means straight line and no ripples.

Thanks.

Lester

[John_P1]

Hi Lester,

The 9234 only has a  23.04 kHz bandwidth which is probably filtering out the higher frequency components of your square wave (it is intended to be used for sound and vibration applications).  Here is a nice illustration from wikipedia that shows how a square wave is made up of a summation of harmonics:

 

So, when you try to represent a square wave with a smaller number of harmonics you will see "ripples" around the edges.  I hope this is helpful in explaining the behavior you are seeing, but please let us know if you have any questions or need help picking out more ideal hardware for your application (we would need more details about what you are trying to do to give a recommendation).

Best Regards,

John