ADS1102CAL (Siglent SDS1102CNL) unwanted signal filtering. - Page 1
Forum section: electronics / testgear

author: markone
author_rank: Frequent Contributor
timestamp: February 19, 2016, 03:24:07 pm
content: Probably it's an already known bug for this not recent scope, that i bought for cheap years ago for simple tasks, but it's quite funny how it shows up.Using one single channel, with sampling rate of 250MSa the signal appears heavily low filtered, in a way that's not achievable even playing with internal digital filter function, this happens with and without the channel BW, on both channels and never happens with both channels enabled.While is marked Atten ADS1102CAL, as we all know, it's actually a Siglent SDS1102CNL and i always used SIGLENT FW releases, for the price paid (235 Euros new) it's a fair device with its big screen and almost dead silent fan, only the trigger section is a bit so so.Some waveform screens in attachment, same signal @ different time scales, the FW is the last available on the Siglent site (5.01.02.32).Now i wonder which kind of algorithm they are using and if exist a way to force it at will with other sampling rate and disable it when not desired.

author: tautech
author_rank: Super Contributor
timestamp: February 28, 2016, 07:21:54 am
content: Interesting, your signal is quite an unusual one with all that noise on it.I've had this thread in an open tab for days till I had a chance for a quiet play.Genuine SDS1072CNL here and I've not seen the unwanted filtering you describe.Signal source SDG1010.BW limit on/off, low/high amplitude signals, over the full S/div range, Peak detect/Sampling acquisition, Eqv/Real time, I've played with all sorts in an endeavour to get a glimpse of that you've posted.In short all that I've seen is exactly as expected.So what tricks must one use to see this behaviour?Which begs the question; we've all assumed the Atten's were exactly the same as the Siglent's, but are they? Could the Atten's have FWto hide what you're seeing and the Siglent's whose FW you are using not?I have no idea on either and last time I asked for info on Siglents various re-brands I was given thetreatment.

author: markone
author_rank: Frequent Contributor
timestamp: February 28, 2016, 04:06:13 pm
content: Quote from: tautech on February 28, 2016, 07:21:54 amThe bad S/N is actual, is from a Picoscope cheap current clamp probe that i discovered to be partially defective just after those measurements, taking it apart i discovered that three voltage bar filtering capacitors were missing (empty marked pcb positions) maybe due to cost saving choice.Mounting three low impedance electrolytic capacitors improved a lot probe's S/N ratio, of course this does not change the weird scope's behaviour that remains still present.Quote from: tautech on February 28, 2016, 07:21:54 amI think the SDG1010 lacks BW to replicate similar dirty signal, where the noise component was quite high in freq, anyway it should be enough to add white noise to a medium frequency square wave.Quote from: tautech on February 28, 2016, 07:21:54 amSame thing here but not with one single channel enabled together those peculiar time base settings, where the unwanted filtering clearly comes up.Quote from: tautech on February 28, 2016, 07:21:54 amAs i previously stated the flashed firmware is from Siglent site, version 5.01.02.32, i assume you have the very same in your scope, UI wise the instrument acts exactly like a Siglent SDS1102CNL from the boot, dunno if we have some logic chip left behind in FW upgrade process.I compared my scope internal content with SDS1102CNL photos / videos found on the web, they seems pretty the same.I also spotted lots of similarity with Rigols DS1000 DSO's HW, starting from PSU's pcbAnyway the funny thing is that i like that filtering, if it were possible to enable it at will