Keysight 4000 X & 6000 X 2000 X 3000 X

[BajanAlan]

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...

[tautech]

Welcome to the forum.

Please tell us more of this trigger problem 

Daniel from Keysight is a member here, maybe he'll respond to you. 
His profile info:
https://www.eevblog.com/forum/profile/?u=114509

[raysem]

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.....

[rx8pilot]

How are they ignoring you?

[raysem]

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.

[RobertoLG]

here is the video about the scopes, if you wanna take a look

https://youtu.be/9x5Ud5bw-bk

[Someone]

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.

[D3f1ant]

I would just just dial in some "holdoff",  then it will trigger correctly in Auto, and still blank the screen if the pulse stops.

[pxl]

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.

[Keysight DanielBogdanoff]

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:

[Keysight DanielBogdanoff]

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.

[Pinkus]

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.

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.

It 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.

[Sbampato12]

I've never noticed this bug. I'll try at home later.

(I want to follow this topic)

[nctnico]

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.

That 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.

[Howardlong]

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.

[HighVoltage]

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 with average turned 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.
 

[Pinkus]

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 all

So 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.

[nctnico]

@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!

[pxl]

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 all

So 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.

Okay, 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.

[Howardlong]

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 ;-)

[Howardlong]

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 all

So 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.

Okay, 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.

It 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 

[Pinkus]

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.

[D3f1ant]

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.

[Pinkus]

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.

Thats 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.

[Howardlong]

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.

Ok, 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.