zero crossing flicker

[thoth]

Hello,

I am doing data acquisition in biological systems, so the levels need to be low.

Unfortunately I am getting zero crossing flicker at levels greater than the acquired signal

(see image in word file). Any ideas how to resolve?

I'm using the USB 6211

thanks

[Hani R]

Hi thoth,

There are a number of things that can be causing the glitch that you are noticing.  The most common reason is due to the glitch energy of a digital to analog converter.  What are you using to generate the sine wave? 

Depending on the application different solutions may be appicable.  For example if you intend on only measuring low frequency signals, a low pass filter may the best solution.  If you are generating higher frequency signals the sample and hold circuit may be more suitable.  Refer to the KnowledgeBase article, KB 0HGFNKBB: Reducing Glitches of Analog Output for MIO Boards, for more details on how to reduce glitches. 

[thoth]

Hi Hani,

Thanks for the reply; I am using Matlab as signal source through the USB 6211 analog output as signal generator. So it seems it's
most likely the source and not the data input.

I may be building a circuit to modify the input impedance so adding a low pass filter for the signal out will be easy. I'll try that.

Thanks

Keith