SDS2000X FFT Speed and Hz/div - Page 1
Forum section: electronics / testgear

author: colorado.rob
author_rank: Frequent Contributor
timestamp: August 06, 2023, 07:35:33 pm
content: I recently watched a video on Siglent FFT Function Basics from TEquipment (link below). The video is only a year old, but appears to be done using an SDS2304X (non-plus version) for the demo. I have and SDS2204X with the latest firmware from Siglent. I tried to replicate this because the FFT performance seemed much better than anything I could achieve on my scope. The video does not go into a great deal of detail on the FFT configuration settings used such as window function and max points. I ran into a few issues when attempting to replicate the results of the video.The resolution bandwidth (Hz/Div) would not go below 250Hz when set to the same sweep speed (20ms/div).The FFT update speed on my scope is significantly slower (~0.7Hz) than what was shown in the video (~2.4Hz).The FFT display is different, showing only 10 horizontal divisions on my scope, with the remainder taken up by the vertical scale on left and right. No vertical scale is displayed in the video.The FFT menu in the video shows different options than the currently released SDS2000X firmware.Does anyone know what firmware version for this scope would reproduce the results in the video? It seems like the behavior I am seeing in the FFT for my SDS2000X shows a regression in behavior.

author: Performa01
author_rank: Super Contributor
timestamp: August 07, 2023, 04:29:58 pm
content: First of all, this video must beveryold. You can tell this from the fact alone that it was done by Steve, the general manager of Siglent North America back then. All application videos from 2016 until today have been done by Jason, an application engineer and not the GM himself.I think this must be an early version of the SDS2000X FW and this is a far cry from today's capabilities and features. The FFT using up the full screen width without any axis labeling is a dead giveaway. Even though window functions have been available back then, we don't know which one has been used for the video. FFT lengt has been a fixed number of 1024. Because of this, a narrow RBW is impossibe to get even at very low sample rates. The low number of FFT points also explains why it could be a little faster.The numbers on the soft buttons do not mean anything like RBW or similar, but simply the graphical zoom of the display.Here you can see a review of this early FFT implementation, still on an even older SDS2304 (without X), but this was the same FFT before the redesign. It was also the time when Siglent scope FW used to be rather buggyhttps://www.eevblog.com/forum/testgear/siglent-sds2000-new-v2-firmware/msg816867/#msg816867Later on, Siglent tried to implement the same FFT (with markers and marker table) as we have it today even on the bottom of the barrel SDS1000X-E series on the soon obsolete SDS2000X, but it was clear from the start that it could be a 64 kpts FFT at most. In the end it turned out that resources in this scope were only sufficient for a 16 kpts FFT and without the marker functions. This is still vastly better than what we had before the redesign.