Would it be possible to add support log-log plotting when using the FFT in math mode in the Oscilloscope GUI? The linear x and y scales are less informative, and it would be nice to quickly check FFTs without needing to change instruments when using the Oscilloscope.

Thank you for sharing this feature and I have let our client team know about your request.

I am not sure about the actual implementation of this however, since the purpose for integrating this into the oscilloscope is to be able to look at the signal in the time domain and frequency domain simultaneously and changing the scale of the math channel would mean changing the scale of the oscilloscope channels which would be even less helpful I think. Also, FFTs are inherently linear since the bins are linear so displaying it as a log scale would mean that your DC to low frequency view would take up most of the screen and your high frequencies would all be a pixel in resolution. I am curious what the benefit would be of being able to view both the FFT on a log scale and the scope on a linear scale at the same time?

Also, just to clarify, our spectrum analyzer is more than just an FFT. For more information on how we implement our SpecAn, please feel free to refer to this application note here.

Thanks! We do a lot of noise mitigation with our experimental set up, so it can be useful to quickly switch between time domain and frequency domain to be able to get a sense of the shapes of intermittent noise, as well as changes to the system when we adjust things like grounding schemes and shielding.

My thought was that it would be fine to have the time domain in linear scale and the freq domain in log-log, as the scales switch anyway when you click between the channel and the math mode (screenshots below from the Moku:Pro demo).

(1) Selecting channel A

(2) Selecting the math channel

As for why we prefer log-log scale over linear for noise, we really like to know the noise performance across the whole range of frequencies (from DC to the Nyquist frequency). Low frequency noise can greatly affect our energy resolution, and we also want to see the response of the detector. Here’s a paper from some of our group a few years ago, see Figs. 4 and 6 for noise plots we regularly make for understanding intrinsic and extrinsic sources of noise.