Hi,

Is there any means of auto-centering the frequency in FFT mode, so that the left hand side of the frequency scale always starts with 0Hz, regardless of horizontal scale?

This would be useful where one wants to zoom out briefly, while still using the full screen horizontal range.

In the attached examples, I needed to make 2 adjustments to keep the screen full - otherwise, I would get an unused negative frequency range to the left of the screen.

For reference, I've also attached a screenshot from Picoscope's FFT mode - you set an upper frequency, rather than Center frequency and Hz/div on horizontal scale.

The short answer is “no”, however here comes the long one:

The Picoscopes have an independent FFT module with a nice and simple user interface. The scope is set up automatically to give you the best possible FFT result. You just need to be careful to not run into aliasing issues – always set the upper frequency high enough so that all frequency components of the input signal are within that span. Use the zoom feature if you want to look at a particular subrange.

The FFT in the SDS1004X-E doesn’t work like this, you need to set it up manually.

Looking at your screenshots, I don’t think this is an optimal FFT setup. You’re using 1Mpts FFT length, yet the resolution is poor at 476.84Hz. With that many points, FFT is not very fast on top of that.

Have a look at the attached screenshot, where I’ve tried to replicate a similar scenario, but with an alternative setup.

I’ve limited FFT length to 32k and set the timebase to 10ms/div. By this I get a sample rate of 500kSa/s, hence an FFT bandwidth of 250kHz where the frequency resolution is much finer at 15.26Hz and the FFT is faster updating too.

I’ve also set a vertical scale of 10dB/div, there’s little point in having more, as the max. dynamic range of the 8-bit FFT in this scope cannot exceed 80dB anyway. Finally I’ve set the reference level in order to make good use of the available screen height.