Siglent SDS1104X-E DC offset thermal drift - Page 1
Forum section: electronics / testgear

author: nixz
author_rank: Newbie
timestamp: December 15, 2022, 01:16:03 pm
content: Hi Guys,I noticed that channels 1, 2 & 3 on my Siglent SDS1104X-E behaves at least strange. When powered on everything to work +/-OK, but after few minutes DC offset of channels 1-3 start to rise from ~0mV to more than 2mV, which makes traces to render out of the screen (500uV/div, AC coupling, nothing connected)! It is interesting that with DC coupling enabled traces are off zero, but not as much as when AC coupling is enabled, also adding 50ohm termination in DC mode influences channel offset (it starts to be positive instead of negative).Interesting thing is that channel 4 i almost OK, drifts only a bit over time and DC is at almost same level as AC...Everything was disconnected from BNC inputs; self-calibration was done several times (and had no impact on channel offsets).I've attached 2 images of channel 1&3 in AC coupling taken 25 sec. and 4:40 after power on.Do you have same issue, any clue how to fix it? Or this is "standard feature" for Siglent SDS1104X-E...best regardsMikolaj

author: BillyO
author_rank: Super Contributor
timestamp: December 15, 2022, 02:31:17 pm
content: I had something similar. Could not get rid of it by doing the built in calibration. I had to send it back to Siglent. Still not perfect, but much better.Now, wouldn't it beVERYhandy to just have a control called, oh.., let's say .. "Offset" where you could just adjust that out?Hmm?

author: nixz
author_rank: Newbie
timestamp: December 15, 2022, 03:29:37 pm
content: Quote from: BillyO on December 15, 2022, 02:31:17 pmAgree: if this is matter of poor factory calibration and thermal drift it shall be redesigned or at least included in self-cal and/or manual offset setting (which currently works the same as position knob).I hoped there is a hole which will fit my screwdriver and I will do offset trim myself...regardsMikolaj

author: pope
author_rank: Frequent Contributor
timestamp: December 15, 2022, 03:37:01 pm
content: I'm trying to replicate what you describe and the scope has been running for over 15 minutes.Hope this helps

author: nixz
author_rank: Newbie
timestamp: December 15, 2022, 04:31:01 pm
content: Quote from: pope on December 15, 2022, 03:37:01 pmThanks, your traces look almost perfect, at least all of them are within visible area and near zeroProbably I have to use warranty to recalibrate my scope. I hope that this is not due to some faulty batch...

author: pope
author_rank: Frequent Contributor
timestamp: December 15, 2022, 04:34:44 pm
content: Quote from: nixz on December 15, 2022, 04:31:01 pmFWIW, I did a self cal after an hour and the results are pretty similar.

author: tautech
author_rank: Super Contributor
timestamp: December 15, 2022, 07:25:09 pm
content: Quote from: nixz on December 15, 2022, 04:31:01 pmYour's might be NIB but is it running the latest FW ?Check the OS version too as if this has been in stock for a while it could be an older production unit that's well behind on firmware.Before fretting about anything check the version installed and update to the latest from here:https://int.siglent.com/download/firmwares/?ProId=12After which run SelfCal ifanynew version is installed.

author: bdunham7
author_rank: Super Contributor
timestamp: December 15, 2022, 07:32:38 pm
content: Quote from: nixz on December 15, 2022, 01:16:03 pmThat seems excessive. Check to make sure that 'Quick CAL' is turned on in the Utility menu. If it is and this behavior persists, you likely need to exchange it.

author: 807
author_rank: Frequent Contributor
timestamp: December 15, 2022, 08:32:05 pm
content: These are the traces of my brand new scope. Taken after being on for nearly an hour. One of them is DC & other is AC coupled. Mean values shown under trace.I watched it from switch-on & the traces hardly moved.nixz...did it stay at those values, or did it move any more at all?sw ver 6.1.37R8

author: nixz
author_rank: Newbie
timestamp: December 15, 2022, 10:41:54 pm
content: Quote from: tautech on December 15, 2022, 07:25:09 pmI've upgraded firmware as a first thing; however, I didn't updated OS. I've run self-cal several times and it do not influence DC offsets anyhow. Here is my current setup:

author: nixz
author_rank: Newbie
timestamp: December 15, 2022, 10:43:53 pm
content: Quote from: bdunham7 on December 15, 2022, 07:32:38 pmI've checked 'quick cal' also without luck. I'm afraid you are right - RMA will be next step...

author: bdunham7
author_rank: Super Contributor
timestamp: December 15, 2022, 10:46:13 pm
content: Quote from: nixz on December 15, 2022, 10:43:53 pmThe fact that shorting the inputs makes a significant difference is a bad sign. I'm not at all sure why you would see that on multiple channels, but something is wrong. Better luck next time!

author: nixz
author_rank: Newbie
timestamp: December 15, 2022, 10:56:08 pm
content: Quote from: 807 on December 15, 2022, 08:32:05 pmMy FW is V6.1.37R9, after warmup only ch 4 is "in range" in AC coupling mode, 1, 2 and 3 are out. In DC coupling they are fair. After cold power on traces in AC are close to "fair" and quickly go out of the screen (hard to catch).See attached screens for exact values:

author: tautech
author_rank: Super Contributor
timestamp: December 15, 2022, 10:58:21 pm
content: Quote from: nixz on December 15, 2022, 10:41:54 pmOS version should be 8.3. There are several additions to the feature set that require this new OS to be installed.It is one of the easiest upgrades as you just place the new OS files is the root of a USB stick then boot the DSO.Just remember to delete them afterwards otherwise they will run each time the DSO boots if left plugged into the USB port.

author: BillyO
author_rank: Super Contributor
timestamp: December 15, 2022, 11:03:33 pm
content: Quote from: bdunham7 on December 15, 2022, 07:32:38 pmThis did not help in my case.Quote from: bdunham7Hmm. For me the problem was only serious in AC coupling and it did not make any difference if the leads were shorted or not. In DC coupling the offset was at least an order of magnitude less and in Gnd coupling there was no offset at all. But shorting the leads in AC coupling did nothing but increase the noise slightly.

author: nixz
author_rank: Newbie
timestamp: December 15, 2022, 11:21:54 pm
content: Quote from: tautech on December 15, 2022, 10:58:21 pmWhere is OS 8.3 on the pagehttps://int.siglent.com/download/firmwares/?ProId=12?I have 8.2 - latest I have found. I've tried FW V6.1.37R9 and older V6.1.37R8 - no change.Interesting is that adding termination on input (50 or 75 ohm) in DC coupling mode moves trace down by ~500uV. In AC coupling mode termination do not influence trace it stays out of screen... This is not true for ch 4 - it works in AC/DC with and without termination

author: tautech
author_rank: Super Contributor
timestamp: December 16, 2022, 12:02:34 am
content: Quote from: nixz on December 15, 2022, 11:21:54 pmhttps://int.siglent.com/upload_file/zip/firmware/Oscilloscope/SDS1xx4X-E_OSV2_EN.zipWhile it is labelled OSV2 it is the 2nd OS release since the original release version so shows in the instrument as V8.3.Edit to addThe OS install is required to obtain full functionality of the new Logging and Clock features.

author: pope
author_rank: Frequent Contributor
timestamp: December 16, 2022, 10:54:48 am
content: Quote from: tautech on December 16, 2022, 12:02:34 amI'm a bit confused. I updated my scope last March and it shows "8.2".Is the .zip you uploaded a newer OS version and if so, should it show "8.3" on the scope after the update?

author: tautech
author_rank: Super Contributor
timestamp: December 16, 2022, 11:04:38 am
content: Quote from: pope on December 16, 2022, 10:54:48 amNormally but not always.If the new features introduced in SDS1xx4X-E_OSV2_EN.zip and FW V6.1.37R9 work as expected then there is no problem however most instruments will display OS 8.3.My pre-public release SN#12 SDS1104X-E shows 8.2 OS but I know the new OS is installed.IDK the reason why this is and only you know if the OS was installed.

author: sonpul
author_rank: Regular Contributor
timestamp: December 18, 2022, 03:42:18 pm
content: My 1202X-E also shows an offset that stops after 30min. One channel is shifted more strongly, the second is weaker. I'm thinking about what to do with it.If you calibrate 30 minutes after switching on, then you need to use it after 30 minutes.If more often the device is needed immediately, then you can calibrate immediately after switching on. But then, after a while, the drift will shift the line, which is what happens with the author of the topic.I think this is due to uneven airflow around the board.The second reason, maybe it's chemical residues after production?Perhaps this is the Thermal EMF of the relay contacts?

author: nixz
author_rank: Newbie
timestamp: December 18, 2022, 09:38:28 pm
content: I've tried this file (8GB and 32GB pen drives) - no action on boot is taken. Instruction says that version 8.2 shall be displayed after upgrade (and I currently have 8.2)...Anyway, this probably will not influence analog frontends of channel 1, 2 and 3. It looks like leakage on the PCB? Something similar was described here:https://www.eevblog.com/forum/beginners/sds1104x-e-ac-coupling-offset/Waiting for response from Siglent distributor in first step they want me to SelCalibrate scope.