Siglent SDS1204CFL - Page 1
Forum section: electronics / testgear

author: Joel_l
author_rank: Frequent Contributor
timestamp: April 06, 2014, 12:44:57 am
content: Hi,I just received my second 1204CFL after sending the first one back because of what I think is poor performance. The waveforms I'm posting links to are from a Siglent SDG5082 which I have been happy with. I have also checked the waveforms against my 11302A which works very well so I am confident the jitter I am seeing is not from the source ( I also tried my 8920B with the same jitter on the 1204 ). Looking at the 1204CFL, the waveforms just seem unstable. Also the P-P voltage is off quite a bit ( 11% ) as displayed and measured on the 1204. When I move the cable over to my 11302a, all looks and measures well. As I have heard asked about other relatively low cost scopes, Am I just expecting too much? I'm considering sending back this second scope and trying an Instek GDS-2204A. Any comments on these videos? They are 20+MB files, so you might want to skip them if you have a slow connection.an 80MHz and 40MHz sine wave. Sampling at 2GSa/Swww.dabbles-n-doodads.com/Scope/vid1.mp4A single 80MHz sine wave at 2GSa/Swww.dabbles-n-doodads.com/scope/vid2.mp4A single 50MHz sine wave at 2GSa/Swww.dabbles-n-doodads.com/scope/vid3.mp4

author: echen1024
author_rank: Super Contributor
timestamp: April 06, 2014, 01:19:13 am
content: Have you tried an autocal?

author: Joel_l
author_rank: Frequent Contributor
timestamp: April 06, 2014, 02:36:28 am
content: First thing I did

author: echen1024
author_rank: Super Contributor
timestamp: April 06, 2014, 02:37:59 am
content: Contact siglent support on this forum, or email.

author: Joel_l
author_rank: Frequent Contributor
timestamp: April 08, 2014, 10:21:49 pm
content: I did hear back from Siglent and was told my issues were addressed in the latest firmware 5.03.02.12, problem is I have 5.03.02.33 on my scope. I have asked about this and am waiting for a reply. I hope this really does address the issues, I really want to like this scope.Joel

author: Deckert
author_rank: Regular Contributor
timestamp: April 08, 2014, 11:45:17 pm
content: Phew, those waveforms do look horrible. I tested a 80MHz square wave on my Atten (Siglent) 100MHz 'scope at 1GSa/sec. The wave is more stable than on your unit, but it is still slightly wavering.I'd say it's the nature of the beast - the digital beast. Switch your display to dot mode with the 80MHz signal, then press RUN/STOP (to stop the sample). You should now see the individual sample dots. Notice the few dots on the rising edge of the signal? That's all the 'scope has to trigger on ... and depending on where the sampled dot is in the wave, the trigger will waver.Switch the display to EquTime instead of Realtime and the wave will be more stable (since it is effectively oversampling the repeating wave and can interpolate the trigger point). The displaylooksjumpy because of the lower waveform update rate. Newer scopes suffer the same problem, but the problem is less noticeable due to the high waveform update rate.Also, can't really see the sampling rate on your vids (video level is blown out), you sure sampling is at 2GSa/sec all the time? Are you using Ch1 and Ch3 when comparing the two signals so that the ADCs are not shared?But still - the shape of your sine wave looks terrible - it should look a lot better when sampled at 2GSa/sec. How does a single-shot trace look like for the sine wave?Single-shot traces from my 100MHz Atten (a Siglent SDS1102CML):Here's an 80MHz sine wave with Sinx interpolation:Here's the same 80MHz sine wave with direct sampling (i.e. connect the dots):And here's the same wave, but with only the sampled dots displayed:--deckert

author: Joel_l
author_rank: Frequent Contributor
timestamp: April 09, 2014, 01:56:46 am
content: ya, the vids are not ideal but I am sure it was 2GSa/S. Maybe I am spoiled by using high end Agilent and Tek digital scopes at work, but I still expect better than what I'm getting. I'm still waiting to see what Siglent has to say about the firmware and if I need to change.Joel

author: Joel_l
author_rank: Frequent Contributor
timestamp: April 09, 2014, 02:45:56 am
content: So I went and took a closer look and sure enough at 2GSa/S I see the dots 500pS apart. This does leave some uncertainty in the trigger. How stable the waveforms are must come down to the methods used to determine where the trigger ought to be. I think I'll try these parameters on one of the Tek scopes I use tomorrow.Joel

author: Deckert
author_rank: Regular Contributor
timestamp: April 09, 2014, 02:12:53 pm
content: Not sure what the Tek's do, but, for example, the new Agilents continuously operate in over sample mode (no dot mode, if I recall).--deckert

author: Joel_l
author_rank: Frequent Contributor
timestamp: April 10, 2014, 02:15:42 pm
content: Siglent got back to me again, did say that the jitter spec was .5 division ( minor division ). Seems to me I see more than that but I guess it is what it is. My scope came with four 300MHz probes, I got around to trying one of those, I'm glad I have other probes. I tried to measure flatness of a sine wave from 10MHz to 200MHz with not good success. I think my setup was partly to blame, but in the end, I don't think I have much faith in what is being measured voltage wise, frequency seems acceptable. Do I think the scope is garbage, probably not, do I think it lives up to its specs, no. I will get out of the performance test mode and try a real world ( for me ) use of the scope before I decide if it goes back or not.Joel

author: Joel_l
author_rank: Frequent Contributor
timestamp: April 10, 2014, 04:33:32 pm
content: OK, so I just reviewed all of my results and compared them to the actual specs for the scope and I think the scope does meet what it should. My last biggest gripe was the voltage measurements. The spec is,DC -10% of rated BW: +/- 1dB10% - 50% of rated BW: +/- 2dB50% - 100% of rated BW: + 2dB/-3dBI think what I measured is actual close to these limits. Next time I will pay more attention to what I should expect from a particular piece of equipment.Joel