Rigol MSO 5000 overshoot, or not overshoot? - Page 1
Forum section: electronics / testgear

author: kehall
author_rank: Contributor
timestamp: July 22, 2020, 09:47:41 pm
content: I'm interested in finding out what other users experiences are with overshoots on the Rigol MSO5000 series...When probe (10x) is connected to the built-in probe compensation output and trimmed to give a flat response at 500mV/div (10x attenuation set), adjust the vertical to 50mV/div.To provide the same starting point, press Default and then Auto when the probe is connected.Which trace best represents what you see on each channel, Ch1 (yellow, with overshoot blip) or Ch2 (blue, flat)?

author: Fungus
author_rank: Super Contributor
timestamp: July 22, 2020, 10:20:19 pm
content: "Overshoot" may be due to overloading the opamps when you send the signal so far off screen.

author: kehall
author_rank: Contributor
timestamp: July 22, 2020, 10:48:51 pm
content: Quote from: Fungus on July 22, 2020, 10:20:19 pmNot really I don't think, you can see the overshoots at higher settings (100-500mV) but not as clearly, the 'zoom in' just helps show it...

author: Fungus
author_rank: Super Contributor
timestamp: July 23, 2020, 06:40:37 am
content: Either way, it's not an amount that would worry me and I don't think it indicates a problem with the 'scope.Wait, I think I'm confused about what I'm looking at.(it happens)

author: tautech
author_rank: Super Contributor
timestamp: July 23, 2020, 09:36:11 am
content: Quote from: Fungus on July 23, 2020, 06:40:37 amIt's more than the max 50mV sensitivity of that FNIRSI thing.

author: Verticon
author_rank: Contributor
timestamp: July 23, 2020, 01:00:17 pm
content: Just some pictures from my Rigol 5074/5354 for comparison. The first one is for channels 1 and 2 and the second for channels 3 and 4. For both records I used the same probe pair which I adjusted for channels 1 and 2. At least for these settings I definitely see no overshoot and all 4 channels seem to behave similarly.

author: Fungus
author_rank: Super Contributor
timestamp: July 23, 2020, 01:27:39 pm
content: Quote from: tautech on July 23, 2020, 09:36:11 amWhy are you obsessed with the FNIRSI thing?

author: Fungus
author_rank: Super Contributor
timestamp: July 23, 2020, 01:32:38 pm
content: Quote from: kehall on July 22, 2020, 10:48:51 pmUnlessallthe signal is on screen then you're overloading the opamps and things like this can happen during their recovery time.

author: Fungus
author_rank: Super Contributor
timestamp: July 23, 2020, 01:34:45 pm
content: Quote from: Verticon on July 23, 2020, 01:00:17 pmAll your signal is on screen. You need to use a signal with a much higher peak-to-peak voltage.

author: kehall
author_rank: Contributor
timestamp: July 23, 2020, 02:15:24 pm
content: Quote from: Fungus on July 23, 2020, 01:32:38 pmI don't think it matters when the data can be manipulated to produce the screen image - are you saying that the opamps are involved when adjusting offset etc? I doubt it - it'll just be a display routine coded accordingly to show the data according to the required parameters surely?Anyway overshoots can be seen when all the signal is on screen so it doesn't agree with your suggestion:Anyway as to it being not significant, if you're investigating a signal that HAS overshoots, how are you supposed to distinguish/make measurements or otherwise trust the display if it can't show a flat response?Either the scope is factory correct or it's not, would you say this is right?

author: kehall
author_rank: Contributor
timestamp: July 23, 2020, 02:18:40 pm
content: Quote from: Verticon on July 23, 2020, 01:00:17 pmI think you're in 1x mode there with 10x probes, so you're really at 500mV there as there's no scaling... set attenuation to 10x and go to 50mV (or 5mV staying at 1x)

author: Fungus
author_rank: Super Contributor
timestamp: July 23, 2020, 02:21:49 pm
content: Quote from: kehall on July 23, 2020, 02:15:24 pmYes.The ADC is 8-bits so apamps are used to scale/offset the signal to fit that range.

author: 2N3055
author_rank: Super Contributor
timestamp: July 23, 2020, 02:43:57 pm
content: Offset Range±1 V (500 μV/div~50 mV/div)±30 V (51 mV/div~260 mV/div)±100 V (265 mV/div~10 V/div)that is at 1x probe setting..But all that is not important. Analog offset is used only for a signal that has larger DC offset and smaller AC component. So you set offset and channel sensitivity until ALL of the signal is on the screen..Dynamic range of scope is a bit more than screen. So if you overdrive input amplifier by signal that would be 20 screens high at that v/div and you're looking at only bottom part of it, you will see overdrive recovery artefacts...This is how it looks on a very expensive R&S RTM3000:https://farm1.staticflickr.com/967/40889430405_8f59935293_c.jpg(from Nctnico's review here :https://www.eevblog.com/forum/testgear/rohde-schwarz-rtm3000-review/msg1604185/#msg1604185)

author: kehall
author_rank: Contributor
timestamp: July 23, 2020, 03:02:25 pm
content: I think we could be getting a little out of scope here (excuse the pun)These overshoots are visible when all the trace is on screen per my post abovehttps://www.eevblog.com/forum/testgear/rigol-mso-5000-overshoot-or-not-overshoot/?action=dlattach;attach=1029846;image;They scaleperfectlywhen altering vertical (yes some signal off screen then but I wouldn't call this particular phenomenon overdriving the amp).Channel 2 blue trace, does NOT exhibit any overshooting at all right down to the lowest mV/div. The first image in this post shows both channels to the same source, same settings (except offset to compare), yet show completely different visual trace. Ch3 and 4 on that scope were also 'flat'.... image below with both channels same source, same settings, no offset, overlaid, no difference if probes swapped.I know there are other MSO5xxx scopes (I had one briefly before it developed another fault) which do not have thes issues. The whole idea of this poll is to determine what other owners MSO5xxx scopes are like, I feel this is down to inadequate factory calibration.Here's the CH2 blue trace all on screen to compare with CH1 in earlier post.. apologies the scaling wasn't set to 10x so it says 50mV but really 500mV/div

author: Fungus
author_rank: Super Contributor
timestamp: July 23, 2020, 03:20:34 pm
content: Quote from: kehall on July 23, 2020, 03:02:25 pmThe calibration signal is 3V peak to peak and you only have 0.2V on screen. It's overloading the amp.Does it happen when all the signal is on screen?

author: kehall
author_rank: Contributor
timestamp: July 23, 2020, 03:30:43 pm
content: Quote from: Fungus on July 23, 2020, 03:20:34 pmyes in the post you replied to earlier...https://www.eevblog.com/forum/testgear/rigol-mso-5000-overshoot-or-not-overshoot/msg3151988/#msg3151988

author: Sighound36
author_rank: Frequent Contributor
timestamp: July 23, 2020, 03:47:02 pm
content: It is odd that some of these suffer form this and others do not, both of our 5000 do not have this issue, neither do the 7000 or 8000's.Maybe a correlation or FW and SW may yield some common ground?

author: 2N3055
author_rank: Super Contributor
timestamp: July 23, 2020, 04:14:00 pm
content: Quote from: kehall on July 23, 2020, 03:30:43 pmSorry we are bothering you but photos are screwed up....If I squint on thumbnail i can see it, but enlarged photo is something else...Try inserting photos inline-full size..If all the signal is on the screen and there is still over/undershoot and signal is not so fast to prompt Gibbs artefacts, than scope is not right..

author: kehall
author_rank: Contributor
timestamp: July 23, 2020, 04:41:39 pm
content: Quote from: 2N3055 on July 23, 2020, 04:14:00 pmInteresting.. I was getting the same image issue in another thread from someone else's images (noreply in the 5000 bugs thread)... I think there's probably some web cache/CDN broken somewhere along the line?I have changed the post to "attachimg=" rather than "attach=", will update the others too. Had to actually re-upload too.. So maybe eevblog needs an ANALYZE / REPAIR TABLES or similar if the images DB is getting messed upUPDATE: I had to edit the post with the full size ch2 blue trace again and re-upload as I checked on another browser and it was FUBARed so clearly there's something weird going on with image uploading/caching (everything looked ok with original browser having cached the images)

author: kehall
author_rank: Contributor
timestamp: July 23, 2020, 04:43:20 pm
content: Quote from: Sighound36 on July 23, 2020, 03:47:02 pmHave you voted in the poll?

author: Sighound36
author_rank: Frequent Contributor
timestamp: July 23, 2020, 05:28:04 pm
content: Yes I have now Kehall

author: tv84
author_rank: Super Contributor
timestamp: July 23, 2020, 05:50:01 pm
content: The forum continues with big problems in the attachmentsbut I've seen no msg from Dave about what they are doing to solve it...(sorry for OT)

author: Fungus
author_rank: Super Contributor
timestamp: July 24, 2020, 08:53:36 am
content: Quote from: kehall on July 23, 2020, 03:30:43 pmThat image wasn't there earlier.Still looks like ordinary probe compensation problems to me. I find it very, very hard to believe that it could overshoot like that on a 1kHz square wave.nb. Compensation signals aren't usually very good square waves and you won't get a perfect square corner using one. Tweak it so there's no "overshoot" then go look at a better signal.

author: kehall
author_rank: Contributor
timestamp: July 24, 2020, 09:36:15 am
content: Quote from: Fungus on July 24, 2020, 08:53:36 amTrust me it's not a compensation issue - the slope is far too abrupt... see this when adjusted...

author: Weston
author_rank: Regular Contributor
timestamp: July 24, 2020, 05:25:44 pm
content: This looks like a HF compensation issue. Does it change when you swap probes between channels? Have you been adjusting the HF compensation trimmers in addition to the LF compensation trimmer?Most probes have more than one compensation trimmer, the additional ones determine the wave shape for the first few hundred ns or so of the compensation signal.

author: kehall
author_rank: Contributor
timestamp: July 24, 2020, 05:46:46 pm
content: Quote from: Weston on July 24, 2020, 05:25:44 pmSorry but it is NOT a compensation issue, despite how it looks.This poll and thread is about a hardware problem with the Rigol MSO5xxx scope - where overshoots are present on some or more channels, or not, same, different probes etc, and cannot be adjusted away. Some users have replaced an lfcal.hex file on the scope and it's been fixed, some have returned and have replacement mainboards and fixed. Some have had no problems at all (the majority by the poll so far).I am just trying to gauge how many people have the same problem, or not as the case may be as Rigol seemingly have an issue with factory calibration.

author: Pulsepowerguy
author_rank: Regular Contributor
timestamp: July 26, 2020, 12:13:24 am
content: Quote from: kehall on July 23, 2020, 04:43:20 pmI would vote, but my scope's channel 2 has an undershoot problem (as I posted earlier). This occurs with direct (BNC) coupling as well.

author: Fungus
author_rank: Super Contributor
timestamp: July 26, 2020, 09:21:17 am
content: Quote from: kehall on July 24, 2020, 05:46:46 pm(Says the guy who though vertical scale/offset was done in software...)If it's a new 'scope, if itonlyhappens on one channel, if it happens identically with all four probes, if it can't be calibrated away, if it happens on signals other than the calibration test signal,thenit might be faulty component in the input circuitry or some bad soldering. Ask for a replacement.

author: 2N3055
author_rank: Super Contributor
timestamp: July 26, 2020, 09:43:41 am
content: This is exactly how it looks when HF compensation on a probe is not set correctly.You MUST verify scope input with a 50 ohm terminator on the input run by pulse coming from 50 OHm pulse gen. And do that on several frequencies...And have all of the signal on the screen... If that shows this distortion, return the broken device..

author: kehall
author_rank: Contributor
timestamp: July 26, 2020, 09:45:36 am
content: Quote from: Pulsepowerguy on July 26, 2020, 12:13:24 amI looked at your image too, it looks like a different issue as your ch2 is as you say almost a continuous slope, slow response, whereas this poll is covering a very definite 'fast' overshoot. I do agree though, these scopes seem to have a little 'spotty' QA coming out of the factory - there's clearly very good examples out there and a few bad ones - I put it down to lack of training or rushing without due care in cases like this.