Keysight 4000 X & 6000 X  2000 X 3000 X - Page 1
Forum section: electronics / testgear

author: BajanAlan
author_rank: Newbie
timestamp: April 17, 2016, 10:58:46 pm
content: mjlorton - I chat about the trigger "fix" / enhancement that Keysight say they are implementing on their 4000 X & 6000 X series oscilloscopes...but not the 2000 X and 3000 X series...

author: tautech
author_rank: Super Contributor
timestamp: April 17, 2016, 11:26:00 pm
content: Welcome to the forum.Please tell us more of this trigger problemDaniel from Keysight is a member here, maybe he'll respond to you.His profile info:https://www.eevblog.com/forum/profile/?u=114509

author: raysem
author_rank: Newbie
timestamp: April 18, 2016, 03:33:44 am
content: I have been working with a 2000 series for a number of years now, and am looking to purchase a new o'scope later this year.I am certainly NOT happy that Agilent (or Keysight, or whatever their name is this week) has chosen to ignore owners of the 2000 & 3000 series.Keysight will NOT be getting any purchases from me.....

author: rx8pilot
author_rank: Super Contributor
timestamp: April 18, 2016, 03:38:25 am
content: How are they ignoring you?

author: raysem
author_rank: Newbie
timestamp: April 18, 2016, 04:35:51 am
content: It's a triggering problem with low frequency signals. The o'scope will trigger poorly (or not at all) in AUTO mode on a 1Hz signal. See the video from mjlorton for details.

author: RobertoLG
author_rank: Frequent Contributor
timestamp: April 18, 2016, 04:39:29 am
content: here is the video about the scopes, if you wanna take a lookhttps://youtu.be/9x5Ud5bw-bk

author: Someone
author_rank: Super Contributor
timestamp: April 18, 2016, 05:37:14 am
content: Its not like you can't tell if the scope is triggering or not, there is a specific indicator for that at the top of the screen. I've never seen the attraction of Auto trigger when there is a force trigger button on the front panel.

author: D3f1ant
author_rank: Frequent Contributor
timestamp: April 18, 2016, 05:37:29 am
content: I would just just dial in some "holdoff", then it will trigger correctly in Auto, and still blank the screen if the pulse stops.

author: pxl
author_rank: Regular Contributor
timestamp: April 18, 2016, 06:42:33 am
content: Hmm, I think the scope does this thing right. In auto mode it is not expected to trigger, because it is auto triggered already. In this aspect, I don't know what the Tek does at all?As long as the scope emits a trigger signal (blinking a led, or through the trigger out bnc) this behaviour seems expected and ok.

author: Keysight DanielBogdanoff
author_rank: Unknown
timestamp: April 18, 2016, 03:45:03 pm
content: Hi! The Auto trigger works the same across the scopes you listed. Basically, once it gets a valid trigger it waits for a short bit for another valid trigger. If it doesn't get one after this time, then it goes into a free run mode where it acquires and displays as fast as it can.The best bet here, especially with a 1 Hz signal, is to go into "normal" triggering mode. There's a post on our blog about auto vs. normal triggering:https://keysightoscilloscopeblog.com/and a video on our YouTube channel with a quick demo:

author: Keysight DanielBogdanoff
author_rank: Unknown
timestamp: April 18, 2016, 03:57:22 pm
content: Ok, I just watched the video. That's a bit weird, I'll talk with the support folks and R&D and try to figure out what's going on.

author: Pinkus
author_rank: Frequent Contributor
timestamp: April 18, 2016, 04:27:20 pm
content: To save time, you may jumpt to minute where 27:30 Martin is showing the problem in detail.Thanks for you feedback and for taking care Daniel.Quote from: Keysight_DanielBogdanoff on April 18, 2016, 03:57:22 pmIt is not weird, it is absolutely annyoing - every day..When working on unknown signals, I often have to switch the trigger back and forth from 'normal' to 'auto' and vice versa and each time I swear about my Keysight scope. My MSO3000X series scope did cost (with options) $15K when purchased. Hello!!! we are not talking about a $800 Chinese scope with limited support (and even there e.g. Rigol is bringing out bug fixes even on older scopes). This is a scope from a reputable manufacturer where customers can be certain (well, not anymore?) that bugs will be fixed.The reputation of Keysight was build up by the "we care"-habit of HP an Agilent. I doubt declining bug fixes on products which are still beeing sold were common.Building up a brand is difficult and a long and difficult way, damaging it is easy and quick. See Tektronix (Danaher). I wonder what road Keysight is now taking.

author: Sbampato12
author_rank: Regular Contributor
timestamp: April 18, 2016, 04:47:13 pm
content: I've never noticed this bug. I'll try at home later.(I want to follow this topic)

author: nctnico
author_rank: Super Contributor
timestamp: April 18, 2016, 04:56:04 pm
content: Quote from: raysem on April 18, 2016, 04:35:51 amThat is normal because the auto trigger interval is faster than 1 Hz. It is like this on any oscilloscope regardless the brand (except for Tektronix). Either use the normal trigger mode or roll mode. The reason why it works on the Tektronix scope is because Tektronix has a much longer auto trigger delay after it has found something to trigger on. Being a long time Tektronix user myself I have found this behaviour can be annoying in some cases because it can take long for the oscilloscope to show a signal again after a trigger. So all in all there is no optimal solution here.For the situation mjlorton shows the better option is to use roll mode because then you can also see the interval between the pulses. Just looking at pulses isn't a good way of verifying firmware or a circuit in the first place.You could argue to make the auto trigger time also depend on the trigger hold-off time which Keysight could build into their oscilloscopes. This would give the user control over the auto trigger interval.

author: Howardlong
author_rank: Super Contributor
timestamp: April 18, 2016, 05:25:08 pm
content: Exactly!The problem with the Tek way is that if you're just probing around a circuit, you have to wait for the auto timeout, and it's not immediately clear whether the pin is really oscillating or it's at a steady level, you have to wait. On the Agilent you can see right away if the signal's high or low, or whatever voltage it might be, as well as whether it's oscillating right away.This has been covered before.https://www.eevblog.com/forum/blog/eevblog-617-tektronix-oscilloscope-anomaly/I also did a very short vid comparing a Keysight 7000, Rigol MSO1074Z, Tek TDS2024 and a Tek MDO3000 in Auto.What is more confusing is what the "enhancement" is on the X 4000 and X 6000, I am not sure how you can cover both options, although I could see that you could choose one auto mode over another.It's not a bug as far as I am concerned, it's the way it works. Martin may think it's a bug, I don't, and I personally prefer the Agilent way for the reason stated, and I've only started using Agilent/Keysight scopes in the past 18 months having been a Tek man most of my career.Edit: typos, bloody tablets.

author: HighVoltage
author_rank: Super Contributor
timestamp: April 18, 2016, 05:49:20 pm
content: I don't see a "problem" here at all and I am using the 2000X, 3000X and 7000 series scope sometimes on slow 1 to 2 Hz signals. There always has been one setting that was perfect for each job.The only wish I had for slow 1 Hz signals would be, the scope working withaverageturned on.But that also does not work with modern Tek scopes.However, this works perfectly with some older Fluke / Philips Combiscopes.So, no scope is perfect for every job.

author: Pinkus
author_rank: Frequent Contributor
timestamp: April 18, 2016, 06:13:01 pm
content: Well, see the attached pictures:· 2.6 Mhz pulse (80ns wide): everything is fine· 100 Khz, fine· 1 Khz, dim but triggered· 20 Hz, dim but triggered· 9 Hz, not triggered anymore. The scope shows no signal at all, sometimes you see something like a glitch - but not at the expected trigger position· same as above with permanent display on: you see the scope is not triggering at allSo you tell me, this is normal that a scope is not triggering at all in Auto mode on 10 Hz signals?No way! No wonder, Keysight is correcting this behaviour on the 4000x and 6000x series.Edit: Changed the 5th picture because it was made in AC mode (showed the same, but I wanted the same scope condition for all screen shots). Now it is in DC mode too.

author: nctnico
author_rank: Super Contributor
timestamp: April 18, 2016, 06:38:58 pm
content: @Pinkus: I just checked on another scope (Gw Instek) and that looses trigger below 2 Hz. But again: this has to do with the auto-trigger timeout which is a trade-off between how long it takes to display a signal without a trigger and the lowest frequency to trigger on. The 'fix' from Keysight will be to make the timeout slightly longer but don't expect a radical change here!

author: pxl
author_rank: Regular Contributor
timestamp: April 18, 2016, 06:45:34 pm
content: Quote from: Pinkus on April 18, 2016, 06:13:01 pmOkay, that is a bit different case. I think to lose the triggering at 2 Hz perfectly normal and expected. Losing at 10 Hz, even getting unstable at 1 kHz is probably not the best, indeed.

author: Howardlong
author_rank: Super Contributor
timestamp: April 18, 2016, 06:46:47 pm
content: Pinkus: the behaviour seems reasonable enough to me. They just work in different ways, it is not a bug as far as I am concerned. I could see the "enhancement" being an adjustable operation.Needing to switch between Normal and Auto is a common thing to do on any scope I've ever used, Tek, Keysight or any other. I am not sure what the problem is other than your scope lacks a telepathy function ;-)

author: Howardlong
author_rank: Super Contributor
timestamp: April 18, 2016, 06:50:12 pm
content: Quote from: pxl on April 18, 2016, 06:45:34 pmIt is not "unstable", it is dim, that is the point of the intensity knob. I just don't understand the problem here, it sounds more like needing to understand how your instrument works a bit better

author: Pinkus
author_rank: Frequent Contributor
timestamp: April 18, 2016, 06:57:35 pm
content: well if I would be a scope (not that I want to be one, seems to be a pretty boring life) ... and if I would be waiting for a signal for a second .... I would place the beginning of the long awaited signal at the trigger point.

author: D3f1ant
author_rank: Frequent Contributor
timestamp: April 18, 2016, 07:04:17 pm
content: I don't think this is a bug either, this seems to me to basic operator error.Just because you turn on Auto trigger doesn't mean you don't have to setup trigger levels or holdoff if you want to display a signal clearly and repeatably. Trigger level and holdoff (along with more advanced trigger settings) settings work the same in Auto as they do in Normal.Keysight scopes just seem to have very fast rearming after an auto trigger, that's a good thing if your hunting around for a unknown signal.

author: Pinkus
author_rank: Frequent Contributor
timestamp: April 18, 2016, 07:32:21 pm
content: Quote from: D3f1ant on April 18, 2016, 07:04:17 pmThats not the point. The point is,that the scope is NOT triggering at all in Auto mode with non-repetitive signals.Even when there is only one short signal in 10 seconds: the scope will NOT trigger. I know what to do with holdoff and of course trigger level etc. are set.But here there is a scope in Auto-Trigger mode, waiting a second or longer for a signal. Then a signal appears and .... the scope will not trigger on it. So you miss it.

author: Howardlong
author_rank: Super Contributor
timestamp: April 18, 2016, 07:52:49 pm
content: Quote from: Pinkus on April 18, 2016, 06:57:35 pmOk, and then how long do you hold that trace for? The problem with the Tek way is that it holds the trace for a short period of time before re-enabling the trigger, which when you're probing a circuit means you don't get immediate feedback.I understand where you're coming from, I just don't see it as a bug, it's just the way some scopes work differently to others, and personally I prefer the immediacy of the Keysight style auto trigger.Another possibly more serious problem with the Tek method is that if your trigger level isn't within range, you will almost certainly never see an infrequent pulse outside of trigger range because te re-arming of the trigger is so infrequent using the Tek method. Here's an example comparison, a 1kHz 2us wide pulse.

author: lem_ix
author_rank: Regular Contributor
timestamp: April 18, 2016, 08:17:09 pm
content: Was working on a pulse oximeter(same frequency), and ofc used roll off mode on my hameg to display the signal. It's not a bug, rather the way the tool works. I like that it shows stuff even when I'm not triggering so I know something is there. To each their own i guess?

author: Howardlong
author_rank: Super Contributor
timestamp: April 18, 2016, 08:19:21 pm
content: Quote from: Pinkus on April 18, 2016, 07:32:21 pmThe Keysight _will_ trigger if the timebase is appropriately slow for a given signal.But what you are describing is what Normal mode is for.The Tek, by the way, does not trigger at all at 40ms/div and slower, it goes into untriggered Roll mode automatically on Auto. You have to switch the trigger to Normal to allow triggering (errr!). Here is a 6.3Hz 9.7ms pulse, the Keysight triggers, the Tek does not.

author: D3f1ant
author_rank: Frequent Contributor
timestamp: April 18, 2016, 08:51:13 pm
content: Because its early and I had just enough coffee to be bothered I am trying to replicate. I have a sig gen putting a 1us pulse, 1Hz. I set scope to Auto trigger, scope displays the signal intermittently, so I can immediately see there is something there, I twirl the holdoff knob for stability and bingo I have a perfectly centered blip (or pretty trace) depending on where I have timebase. If I take the signal away the trace goes back to flat line. Where is the problem?I'm not sure how your setting up your scope that you don't see the intermittent pulse at least somewhere on the screen. If your timebase is set extremely slow and you have your scope set to hi-res or some other averaging/filtering/bw limit turned on maybe it wouldn't display at least 'something' but thats still a setup problem. I would think you would/should normally have a fair idea of what a signals parameters should be and setup accordingly.

author: Keysight DanielBogdanoff
author_rank: Unknown
timestamp: April 18, 2016, 10:05:37 pm
content: Hi everyone, I spent the afternoon getting down to the nitty gritty. I love my job!Essentially, it comes down to an ideology that we hold here at Keysight scopes. That is: “Don’t compromise the waveform update rate!”Keysight auto trigger mode works like this:0. Assume a stable trigger was found1. Wait for another valid trigger eventa.wait time = maximum of (4 * total time on screen) or 50 µsi.note: on the 2000 and 3000A scopes, the wait time = maximum of (1/2 * total time on screen) or 50 µs. This is what we changed in firmware.b. If a valid trigger event is found before (a) has passed, repeat (1)c. If no event found, go to (2)2. Enter “autotrigger” (or free-run) mode: acquire and display signals as fast as possiblea. The “as fast as possible” will be the fastest update rate available at that time/div setting3. While doing (2), check trigger circuitry every 250ms to see if there was a valid trigger event in the past 250 msa. If there was a valid event, go to (1)b. If there wasn’t a valid event, go to (2)So here’s what is happening. For the 1 Hz cardiac pulse, because the pulses are so far apart and only happening once, the scope essentially stays in auto trigger mode (2). E.g. if there was a pulse in the previous 250ms period then it will wait for another pulse, but will time out before the required 750ms has elapsed unless the time/div setting is high enough (see 1). For example, put the cardiac pulse on and set the time/div to 25ms. Because the screen is then showing 250 ms of time, the wait period will be 4*250 ms = 1s and you will see the regular trigger.What Tek and some other vendors do is build in a wait time after every single capture. I think Tek has an initial wait time of 4*time on screen, the switches to 2*time on screen after each subsequent trigger event. We spend the majority of the free-run time (2) acquiring and plotting instead of waiting.The 3000T, 4000 X-Series, and 6000 X-Series scopes all follow the 1a guidelines, while the older 2000 X-Series and 3000A scopes keep the 1ai scheme. Ultimately, I don’t see this as a bug. I’m not just saying that because I work for Keysight, but as I’ve looked at this closer it seems to be more of a difference in ideologies about how auto trigger mode should work and how auto trigger mode is implemented, especially in the free-run portion of the state machine.Another thought I had here is that our built-in DVM could run on the side and let you know immediately if the pulse stops because the frequency will change. Our DVM will work on the same channel you are probing, too, so no extra probing is necessary.I hope this makes sense, I’d be happy to discuss further or clarify if I wasn’t clear enough.

author: lem_ix
author_rank: Regular Contributor
timestamp: April 18, 2016, 10:22:35 pm
content: Great explanation! Not sure if a case of RTFM? Include such information if it's not in there already. Normally you would find a solution the moment you encounter such a signal but it can't hurt to point it out

author: Keysight DanielBogdanoff
author_rank: Unknown
timestamp: April 18, 2016, 11:02:14 pm
content: I don't think it's an RTFM (read the factory manual) situation, it's sort of a obscure spec/feature/characteristic. I definitely see how it could be confusing or look like a bug.

author: tautech
author_rank: Super Contributor
timestamp: April 18, 2016, 11:37:55 pm
content: Quote from: Keysight_DanielBogdanoff on April 18, 2016, 11:02:14 pmNearly Daniel, it's read the f**king manual.Good to see the trouble you've gone to in order to check the OP's problems out.

author: Sbampato12
author_rank: Regular Contributor
timestamp: April 19, 2016, 11:33:20 am
content: It is very great to have a employee that use the same forum you use!Looking foward, sure it is more a characteristic than a bug. And in comparison as some users posted here, I think that this is the most interesting approach.Anyway, this was good to learn a little bit more on triggers!

author: Dubbie
author_rank: Unknown
timestamp: July 27, 2016, 04:41:34 am
content: After upgrading from my Rigol to a Keysight 3000T, this one caught me by surprise. I couldn't figure out why I suddenly couldn't trigger at all on sparse (10ms) signals. On auto they were just jittering around all over the screen. The manual wasn't very helpful but this thread cleared things up for me. Putting a long holdoff made it settle down.

author: LabSpokane
author_rank: Super Contributor
timestamp: July 27, 2016, 04:30:41 pm
content: And this is why I will continue to buy from Keysight.

author: taemun
author_rank: Regular Contributor
timestamp: July 27, 2016, 04:41:47 pm
content: Isn't the real KS deficiency here that the scope can't detect a trigger mid-acquisition, and move the trigger-point to the appropriate place on the x-axis?If it did that, wouldn't everybody be happy?Disclaimer: happy MSOX3054A owner over here

author: Dubbie
author_rank: Unknown
timestamp: July 29, 2016, 07:05:16 am
content: I would be happy if this was how it worked.Sent from my phone using Tapatalk

author: HighVoltage
author_rank: Super Contributor
timestamp: July 29, 2016, 07:28:03 am
content: On slow signals I just switch from AUTO to MANUAL trigger mode and it works fine on all my Keysight scopes.

author: taemun
author_rank: Regular Contributor
timestamp: July 29, 2016, 07:31:09 am
content: Quote from: HighVoltage on July 29, 2016, 07:28:03 amYou're right, 'Normal' mode triggers only when it should. However, that doesn't really excuse the operation of the 'Auto' mode.I'm wading into a religious debate, but I think that the auto mode could be improved to meet everyone's expectations if the scope could detect and act on a trigger mid-acquisition, rather than just blindly running over it.