New Agilent scopes

[rf-loop]

I've only ever seen alt trigger on a few cheaper scopes - not really sure why you'd want it - I suppose there might be some rare situations where you need to see the shape of 2 unrelated signals simultaneously.

Are you kidding?

Simplest possible example from yesterday. I want compare two separate signal generator waveforms. Both generators have its own clock. (they are not sync with each other but I want look signal shapes with several different settings. Without ALT trig I waste lot of time and time is money.)
Gen 1 to CH1 and Gen 2 to CH2 and compare wafeforms shape, scope to ALT mode. Set CH1 and 2 triggers and go...

How you do it without ALT trig. And this was just as simplest possible example.

I suppose the approach without alternative trigger would be to trigger on one, save it as a reference waveform and then trigger on the other.

Of course this simplified example can do many ways. This was not question. But other this is if it is so handy. Of course I can even take picture and compare these. And if I'm pianist I can push 50 button in second. If Do just one measurement it is not so big problem but if need quickly look (in this tiny example) many or some more...  you can do it, of course but I'm so lazy that I want tools what are handy.

But then if we take littelbit different need..  say example you have system where is some PWM signal but some reason you want watc simultaneously example just 2 or more of them (more scope channels) how they change as you adjust something in system and there is some system relationship between them. Signals are not sync each others and timing is also very different... say other is 1.2MHz and other is 25kHz..  It is just nice if you can use dual timebase separatery trihgged ALT mode. All these simultaneously in realtime under your eyes and need use only one oscilloscope.  Of course also this is possible to do many ways. All can.

Of course, for many peoplses these functions are useless. There is different needs.
But in my opinion ALT trig is basic function and it is shame if this level of oscilloscope do not have it.

[jpb]

I don't disagree that it would be nice to have, especially with different timebases allowed but it is added complexity and hence cost so on low end scopes I guess Agilent (and others) decided against it.

I see that Tektronix has a patent on it:

http://www.google.com/patents/US6473701

perhaps this is another reason why other manufacturers find it simpler not to include it. Though the low end Rigol and Owon seem to have it as an option.

[Hydrawerk]

My Tektronix 7000 have it and more, also Tek 465 have it, Tek 2200 serias have it and Tek2400 serias have it. Do you think they do this feature just for nothing. If professionals do not need it they really do not make it.

OK, but they are older analog scopes where you probably have no Single pushbutton.

It is real shame if this Agilent model do not have it.

Yes, it is.  But I am afraid that most middle class scopes don't have alt Trigger. I mean Rigol DS2000, Agilent DSOX2000 or DSOX3000, Tek DPO2000. Only GW Instek GDS-2000A has the alt trigger. Also some Owons, Siglents and even Rigol DS1000 series.
But even without alt trigger you can always push Run/Stop to see both waveforms with different frequency. 

[rf-loop]

I don't disagree that it would be nice to have, especially with different timebases allowed but it is added complexity and hence cost so on low end scopes I guess Agilent (and others) decided against it.

I see that Tektronix has a patent on it:

http://www.google.com/patents/US6473701

perhaps this is another reason why other manufacturers find it simpler not to include it. Though the low end Rigol and Owon seem to have it as an option.

Owon SDS serie have ALT trig mode (default, not option)
Separate trigger settings.
Separate trig freq counters.
Not dual timebase.
All memory (1k+1k to max 10M+10M)can use for ALT single timebase mode.

Siglent SDS1000(L) serie have ALT trig dualtimebase mode. (default, not option)
Separate trigger settings.
No trig freq counters in this mode.
Also in ALT mode with dual timebase: Tracking cursors can split between channels. Math can do between ALT trigged channels or FFT.
Dual timebase.
Long memory can not use in ALT dualtimebase mode. (fixed 20k+20k)

[rf-loop]

But even without alt trigger you can always push Run/Stop to see both waveforms with different frequency. 

Yes and if looking example risetimes. After stop then try find where is this other channel rising edge.

[marmad]

ALT trig have been normal feature in oscilloscopes as long as I remember.
And this is not enough, there is also ALT trig with real dual timebase. (in history and today but these are not usual in entry level cheap scopes)

In analog scopes specially it is very normal feature in all professional analog scopes (I do not remember any scope what do not have it).

Yes, it has been a standard feature on analog scopes for decades - and very handy in certain circumstances - even though I don't use it that much.

It is real shame if this Agilent model do not have it.

Well, as Hydrawerk noted, the Rigol UltraVision scopes don't have it, the Agilent InfiniiVision X series don't, the R&S RTO series (1M wfrm/s) don't, etc. - so there seems to be a trend of these high waveform capture rate DSOs not having Alternate mode - which makes me think it's connected to maintaining the wfrm/s speed (although GW-Instek seems to have worked out some way to use it on their new GDS-2000A series). I'd love to see tests done on the wfrm/s speed of the Instek when Alternate mode is used.

Edit: Also, I believe all of these fast waveform capture scopes are using digital triggering now - so perhaps the use of digital triggering complicates the implementation of Alternate mode.

[marmad]

Simplest possible example from yesterday. I want compare two separate signal generator waveforms. Both generators have its own clock. (they are not sync with each other but I want look signal shapes with several different settings. Without ALT trig I waste lot of time and time is money.)
Gen 1 to CH1 and Gen 2 to CH2 and compare wafeforms shape, scope to ALT mode. Set CH1 and 2 triggers and go...

How you do it without ALT trig?

Of course this simplified example can do many ways. This was not question. But other this is if it is so handy. Of course I can even take picture and compare these. And if I'm pianist I can push 50 button in second. If Do just one measurement it is not so big problem but if need quickly look (in this tiny example) many or some more...  you can do it, of course but I'm so lazy that I want tools what are handy.

But then if we take littelbit different need..  say example you have system where is some PWM signal but some reason you want watc simultaneously example just 2 or more of them (more scope channels) how they change as you adjust something in system and there is some system relationship between them. Signals are not sync each others and timing is also very different... say other is 1.2MHz and other is 25kHz.

Well, while the Rigol doesn't have the ALT trigger mode, it has many other complex triggers - one of which is called Delay - but it really could be called Dual. It can use both CH1 and CH2 as the trigger source - each on it's own edge, with < / > / <> / >< delay parameters with a large time range. So it's quite easy to set up the scope to display stable waveforms with un-synced signals, as in the attached image; both waveforms were perfectly stable:

[Hydrawerk]

It looks good.

[rf-loop]

Yes, it looks good version of  digital oscilloscope "ALT" by different name and there can select trigger level and time position for each channels.
With this can do many things.

I can not see any signs about dual timebase in pictures.
Dual timebase means that both channels have also separate horizontal speed.
(but in practice, very rare really needed (in ALT mode or delay mode how they name it) but nice to have

[marmad]

Yes, it looks good version of  digital oscilloscope "ALT" by different name and there can select trigger level and time position for each channels.
With this can do many things.

It's not as versatile or easy to use as a powerful ALT implementation - you can only use edge-triggering on each channel (as opposed to different trigger types for each channel) - but it's better than nothing when trying to look at two un-synced waveforms.

I can not see any signs about dual timebase in pictures.

Definitely NOT dual timebase unfortunately.

[rf-loop]

It's not as versatile or easy to use as a powerful ALT implementation - you can only use edge-triggering on each channel (as opposed to different trigger types for each channel) - but it's better than nothing when trying to look at two un-synced waveforms.

Yes, 1-0 better than nothing.
Without this un-sync signals just game over exept if can accep play run/stop game in some cases where it may give some kind of solution for random rare needs.  Perhaps also most of users never need?  But yes I remember one "show". (it was mistake).

People check freq reference using analog oscilloscope. Both channels show 10MHz references outputs. After some short time oscilloscope show nice sinewaves and guy tell me they are exactly. Yes I look also some seconds his scope screen and yes no any detectable shift.  Show was nearly end. But in my head red light go on... wait a minute..  they are normal well adjusted high class  OCXO's.  But red light  in my head becouse it was too stable.... may I look agen. 

Then I ask how you have adjusted these... 

"no no-... I just only connect these for check and they looks very very good so I did not yet adjust. "

Scope was still on. oh... no any drift and there is now long time... minutes. 

ALT !! ... your oscilloscope is in ALT mode! 

turn to CHOP... wau... other channel signal go so fast that can not see waveform at all.
Perhaps tens of Hz difference.

"What is it... why? Normally I do not touch this switch"

[Hydrawerk]

GW Instek scopes are special. They even have the unique split window function. It is like alt trigger mode. Nevertheless, this scope GDS-3000 might not be so popular.

[lewis]

I've only ever seen alt trigger on a few cheaper scopes - not really sure why you'd want it - I suppose there might be some rare situations where you need to see the shape of 2 unrelated signals simultaneously.

The Agilent 3000X and 7000B have alternate trigger, it's very useful for simultaneously displaying edge transitions of a switching waveform. Great for looking at pre and post ringing in switched-mode and PWM applications, and you can immediately see any rise and fall time asymmetry. Saves hopping from the rising edge to the falling edge then back again every time you change some circuit parameter.

I also use it as a debugging tool in microcontroller applications, if you want the scope to trigger of some software event, toggle a spare pin at every event and alternate trigger off that. It's quicker to toggle or xor in software than to keep a pin high for several microseconds and take it low again, and is less likely to upset any time-critical code.

[mikeselectricstuff]

I've only ever seen alt trigger on a few cheaper scopes - not really sure why you'd want it - I suppose there might be some rare situations where you need to see the shape of 2 unrelated signals simultaneously.

The Agilent 3000X and 7000B have alternate trigger, it's very useful for simultaneously displaying edge transitions of a switching waveform. Great for looking at pre and post ringing in switched-mode and PWM applications, and you can immediately see any rise and fall time asymmetry. Saves hopping from the rising edge to the falling edge then back again every time you change some circuit parameter.

I also use it as a debugging tool in microcontroller applications, if you want the scope to trigger of some software event, toggle a spare pin at every event and alternate trigger off that. It's quicker to toggle or xor in software than to keep a pin high for several microseconds and take it low again, and is less likely to upset any time-critical code.

I think you are confusing alternate edge triggering with alternate channel triggering.

[lewis]

I think you are confusing alternate edge triggering with alternate channel triggering.

Aha! I didn't realise you and everyone else were talking about alternate channel triggering because I didn't read the thread properly. You're right, I can't see much use for that either.

[marmad]

Aha! I didn't realise you and everyone else were talking about alternate channel triggering because I didn't read the thread properly. You're right, I can't see much use for that either.

Well, as discussed in the thread, there's an obvious use for it - which is why it's been a standard feature on analog scopes (and many digital ones) for decades. It's not something you need often, but when you need to look at un-synced signals, there is only that (or a trigger which is keyed to both channels).

[Rufus]

Well, as discussed in the thread, there's an obvious use for it - which is why it's been a standard feature on analog scopes (and many digital ones) for decades.

And because it is trivially easy to implement on analog scopes that need to have alternate sweeping anyway.

On digital scopes it is more complicated and the fancier the digital scope is the more complicated it gets.

[Hydrawerk]

Please what's inside the MSO cable? Is there some electronics, maybe ADCs? Or only wires?

[rf-loop]

Please what's inside the MSO cable? Is there some electronics, maybe ADCs? Or only wires?

In same kind of cable and old HP16500B analyzator there was only cable and of course something for impedance but no active components. It (HP system) was just becouse this, advertised with many nice words by HP.
My quess is... only matched transfer lines.

----------------------------------------
And then for "Rufus"  previous msg.
Some kind of ALT is not very difficult. (separate timebase and full separate trig settings for both Channels.
Of course it is slow and it really capture channels ALTernatively independent of timebase. So 2.5ns/div in other channel and 50ms/div in other channels is just pain... but of course always in lab need cup of coffee..

[Rufus]

And then for "Rufus"  previous msg.
Some kind of ALT is not very difficult. (separate timebase and full separate trig settings for both Channels.

That is difficult, menus or something to control two trigger settings, configuration of the hardware to capture alternately in two (or 3/4?) channels. Then when you scroll through or zoom into the deep capture memory - how? controls to scroll/zoom traces independently? what about cursor and measurement functions between traces? Disable them because the traces have no time relationship? There is a whole lot of extra crap required just to support alt trigger, the smarter the scope the more crap there is.

[mikeselectricstuff]

And then for "Rufus"  previous msg.
Some kind of ALT is not very difficult. (separate timebase and full separate trig settings for both Channels.

That is difficult, menus or something to control two trigger settings, configuration of the hardware to capture alternately in two (or 3/4?) channels. Then when you scroll through or zoom into the deep capture memory - how? controls to scroll/zoom traces independently? what about cursor and measurement functions between traces? Disable them because the traces have no time relationship? There is a whole lot of extra crap required just to support alt trigger, the smarter the scope the more crap there is.

The trigger circuit will typically be a DAC and a comparator. As the trigger signals are typically also used for protocol decode and frequency counter, chances are there will usually be a DAC per channel, and they multiplex the comparator output to select channel, so ALT trig would just require the trigger mux to change on alternate sweeps. Things get more messy if you want different timebase settings though, both in terms of hardware/firmware, and user interface.

[marmad]

The trigger circuit will typically be a DAC and a comparator. As the trigger signals are typically also used for protocol decode and frequency counter, chances are there will usually be a DAC per channel, and they multiplex the comparator output to select channel, so ALT trig would just require the trigger mux to change on alternate sweeps. Things get more messy if you want different timebase settings though, both in terms of hardware/firmware, and user interface.

As I mentioned before, the new DSOs with fast wfrm/s update rates all seem to be using digital triggers. This document from Rohde & Schwarz gives a good description of a DSO with digital vs. analog trigger - and why they're more suitable for high-speed waveform acquisition. And I still suspect that this is, at least one of, the reason(s) that ALT triggers are becoming less common on more expensive DSOs.

[hooj]

Guys, can anybody check DSOX3WAVEGEN square wave minimum rise/fall time and overshoot?
Square wave screenshots will be fine :-)

I just want to understand can it be as good as HP 33120A or I have to get real 33120A or something like that :-)

[Hydrawerk]

See datasheets of both instruments...

[hooj]

I can't find datasheet for DSOX3WAVEGEN that's why I ask someone to check square wave in scope.