Is there DC offset after the AD conversion?


shorting all 4 inputs on my QA402 and viewing the noise in the time domain shows that there is a DC offset.

This means that I cannot view the noise at a few uV as I would like to as there is not enough possibility to move the noise curves.

I had the same issue with REW until I asked the author to “ac couple” the output of the AD converter in REW.

Is it possible to make the time domain waveform “AC coupled” all the way to after the AD converter in the software?

Hi @SigurdR, what type of analysis are you needing to do on the noise? Wouldn’t AC coupling introduce a phase shift that you must then contend with? Why not just export the time-domain data and do whatever analysis you need on that? Or acquire the data in real-time via matlab and analyze it that way?

Also, if you stop the acquisition you cna use the mouse middle button to pan around and use the left button to draw a zoom box around what you want to see.

Here’s a zoom of a few samples of noise

Hi Matt,

thank you for your reply.

I want to measure the noise to see how the noise level is in the time domain. Then I can estimate noise RMS. Yes, I see that the software also measures RMS but I am old school and want to see the noise on the “oscilloscope”.

I did not know about the panning or moving the screen around. Thx for the tips! I am now able to do what I want.