My trigger offset jitter problem no changing by offset value. 5,10,15,20,25us... always there, and same.
Sorry, I'm helpless with English translation in Youtube editor... Takes too much time.
I hope, it will be clear without translation.
Hi all,
not long ago
the widely known video blogger Dave Jones from Australia (not Austria),
who runs the EEVBlog site corresponding channel on youtube site
recorded a problem with devices Rigol DS1000Z and DS2000(A)
the issue specifically concerns its 'synchronization systems' {trigger}
I don't have the (1000) device here now, I got it (lend)
but, as you can see, I do have the DS2000 so I'll try to make it with this one just as Dave Jones has shown in his video. Aside the DS2000, I temporarily have the DS4000 which is a bit more expensive than the DS2000. Let's see if the DS4000 has some similar problem or not.
About the Version: [version info]
Dave named three main problems:
1. when DC coupling
jitter occurring at multiples of 5us
2. when AC coupling
1. synchro point drifts away
2. jitter independent of signal frequency and/or form
3. --
I don't have a signal gen at hand- but I do have an ATmega and I can, independently of the quality of the mega-generated signal, demonstrate the very same problems Dave has shown.
[demo of problems follows]
1. confirmed
5us problem -> jitter 10ns
10us: jitter should disappear now, but I can still see it, so I conclude that the (ATmega) signal is simply not fancy enough. (Thus, I can neither confirm nor ...)
2. with DC coupling we can nicely see the signal,
now turning on AC coupling we can't see anything. let's zoom out. we should now see the edge in the center of the screen, what we do see a fairly big misalignment here (->incorrect)
[citing rigol forum response]
I personally never used the AC coupling (and can't really imagine {think of a way} using it). Otherwise the scope works reasonably well and if it wasn't for Dave wouldn't have noticed that problem.
3. Can't observe the problem Dave had. I could imagine that Dave's signal somehow interfered with the holdoff value. E.g. If I change my holdoff value here, I can reconstruct a similar 'situation'. But it doesn't say anything about the proper working of the scope.
[describing how the edge falls into the 'holdoff time']
Thus I can conclude that this 'problem' is not a problem with the scope but a problem with the particular setup {the way its user set up the scope}.
[around 13min]
Trying to reproduce the problems Dave describes I found another problem. Given this specific device that supports external triggering. I'm triggering *the same signal* over the EXT trigger. Firstly, we observe an offset of 10ns. The real signal's pk-pk value is 5V, so considering the fact that the probe is x10 the center is around 2.5V [seeing 254mV]. As soon we're moving the trigger value below 0 {below the signal}, sync breaks down (trigger goes beserk). As soon we're above 440mV {i.e. above 5V}, same thing.
Now let's change to AC trigger. Nothing changed. So there's no way of really triggering AC-style. (There's no AC trigger function.) Rigol could've just left that option out.
[summing up stuff]
[same procedure, 4 problem checks on the DS4024]
no jitter at 0 delay with any of the four sources
plenty of jitter at sufficient nonzero delay, but ONLY with the first two function generators
no jitter at sufficient nonzero delay with the two RF ovenized synthesizers
Now, all the non-Rigol scopes use equivalent time sampling and it seems clear that in the absence of a stable source, such as the synthesizers, the combination of sampling and delay leaves one with a "jittered" presentation after the wandering waveform builds up.
Apparently, the Rigol is doing some analog of equivalent time sampling () since I get exactly the same behavior - OK only with the synthesizer sources.
Incidentally, the Tek scope passes the test because it cheats - it won't let you set the delay large enough to cause a problem.
Anyway, I feel a lot better now knowing that my 1980-1990 scopes are just as good as my 2014 scope!
My trigger offset jitter problem no changing by offset value. 5,10,15,20,25us... always there, and same.
What was your signal source? If the source has that much long period jitter anyway, then the oscilloscope is just going to show that.
I know there's been little to no discussion of the dual-slope triggering "bug" mentioned in the video, but I just wanted to point out that this is not a bug at all, rather an artefact caused by trigger holdoff working correctly.
So I put together a quick little video explaining how trigger holdoff causes the observed behaviour -- and I also show how holdoff (even the default, minimum setting) could cause real confusion even if you're using normal edge triggering. This is not Rigol specific, this applies to any scope (with a trigger). With the DS2202 @ factory default settings, these problems could potentially (in admittedly somewhat contrived circumstances) bite you at frequencies as low as 5 MHz.
Why do the DS1000Z and DS2202 behave differently in the EEVBlog video? Because the default(=minimum) holdoff of the DS1000Z, 16ns, is less than the 100ns of the DS2202. 16ns fits inside a 20 MHz pulse (25 ns), 100ns does not. Neither is right nor wrong, and both can be configured to behave as desired.
I made a quick test with a DS4054 and the effect can not be observed there. Dual slope trigger is stable and does not change with holdoff. I believe your explanation is correct, I'm just wondering how they made it work on the DS4000.
BTW: I also can't see AC coupling problems on my scope
http://youtu.be/Z6i9-pQ-kNk
MSO4054 at various delays and beyond, sorry for the ultra crappy webcam footage. (firmware = 2.02.SP1, hardware version = 1.3)
20Mhz, square, 5Vpp, AC/DC coupling has no effect.
If your talking about the delay jitter, I found it on my 4000:MSO4054 at various delays and beyond, sorry for the ultra crappy webcam footage. (firmware = 2.02.SP1, hardware version = 1.3)
20Mhz, square, 5Vpp, AC/DC coupling has no effect.
....What was the signal source?
Did you try making small variations to the frequency?
What was the signal source? This is the kind of result I might expect when using a dithered 1 GS/s DDS to produce square waves.
Playing around some more. Notice how memory depth/averaging change the artifact behaviour.
Also notice when scope is stopped, horizontal position changed, the artifacts disappear.
(MSO4054, random 16Mhz TCXO, DC trigger coupling, 100us delay is roughly the worst point, does not disappear every 5us like Dave's, self cal last night - think Rigol mentioned doing this)
Playing around some more. Notice how memory depth/averaging change the artifact behaviour.
Also notice when scope is stopped, horizontal position changed, the artifacts disappear.
(MSO4054, random 16Mhz TCXO, DC trigger coupling, 100us delay is roughly the worst point, does not disappear every 5us like Dave's, self cal last night - think Rigol mentioned doing this)Do you have a 10MHz reference available? Would you mind testing it again with an external 10 MHz?
No problem, 10Mhz OCXO: