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recent experience shopping for hobby scope in today's market. tek, rigol, ...

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David Hess:

--- Quote from: zrq on February 26, 2023, 02:17:22 pm ---
--- Quote from: David Hess on February 26, 2023, 01:53:30 pm ---My point is that the delayed triggering capability makes up for the short record length in most cases, and it has nothing to do with repetitive signals; it works fine in single sweep acquisition mode.  The TBS1000C can view portions of a waveform at high sample rates at any point after the trigger, where DSOs without this feature are limited by their record length.
--- End quote ---

You are right if the interesting short time feature is appearing repetitively at a predictable interval after some triggerable event. Which is arguably not so common.
--- End quote ---

The more useful feature, which all of the DSOs under discussion lack, is trigger after delay, which is what you get with a dual delayed timebase with two sweeps and two triggers.

After the first trigger, there is an adjustable delay, and then a second trigger produces the acquisition.  For instance when probing a switching power supply, this allows locking onto the reverse recovery waveform even in the presence of jitter.

In the past this was used to trigger at the start of a video frame, and then select a horizontal line to display with no jitter.  No amount of record length can correctly display that in real time; it requires the second trigger.

bdunham7:

--- Quote from: David Hess on February 27, 2023, 02:55:16 am ---The more useful feature, which all of the DSOs under discussion lack, is trigger after delay, which is what you get with a dual delayed timebase with two sweeps and two triggers.

After the first trigger, there is an adjustable delay, and then a second trigger produces the acquisition.  For instance when probing a switching power supply, this allows locking onto the reverse recovery waveform even in the presence of jitter.

--- End quote ---

If you wanted an entry-level scope with retro features, the elderly but still produced Siglent SDS1102CML actually is sort of interesting.  It doesn't have an explicit B-sweep or B-trigger, but it does have trigger delay and I think you could manage something close using the alternate trigger, some holdoff and the rather odd dual-timebase feature where each channel can have independent horizontal settings.  You would have to feed the signal into both channels, which is somewhat of a gnarly probing issue, and I haven't tried it so I'm just speculating.  Other retro features include the 50GSa/s ETS and video triggering.

You're right that trigger delay is limited by record length, but that can be many thousands of divisions depending on your scope and setup.

2N3055:

--- Quote from: David Hess on February 27, 2023, 02:55:16 am ---
--- Quote from: zrq on February 26, 2023, 02:17:22 pm ---
--- Quote from: David Hess on February 26, 2023, 01:53:30 pm ---My point is that the delayed triggering capability makes up for the short record length in most cases, and it has nothing to do with repetitive signals; it works fine in single sweep acquisition mode.  The TBS1000C can view portions of a waveform at high sample rates at any point after the trigger, where DSOs without this feature are limited by their record length.
--- End quote ---

You are right if the interesting short time feature is appearing repetitively at a predictable interval after some triggerable event. Which is arguably not so common.
--- End quote ---

The more useful feature, which all of the DSOs under discussion lack, is trigger after delay, which is what you get with a dual delayed timebase with two sweeps and two triggers.

After the first trigger, there is an adjustable delay, and then a second trigger produces the acquisition.  For instance when probing a switching power supply, this allows locking onto the reverse recovery waveform even in the presence of jitter.

In the past this was used to trigger at the start of a video frame, and then select a horizontal line to display with no jitter.  No amount of record length can correctly display that in real time; it requires the second trigger.

--- End quote ---

Of course even the cheap digital scopes have that functionality. On SDS1000X-E it is called interval trigger.

You have one trigger satisfied, then time limit and then when second trigger comes in, you capture the buffer.

On cheap DS1000Z you have similar Delay trigger and  N-th edge trigger, where you can choose both time delay and number of edges.

On more expensive scopes more sophisticated version is  called Qualified trigger, where you can actually mix and match trigger types.

For video you have video triggers.

David Hess:

--- Quote from: 2N3055 on February 27, 2023, 07:42:39 am ---
--- Quote from: David Hess on February 27, 2023, 02:55:16 am ---The more useful feature, which all of the DSOs under discussion lack, is trigger after delay, which is what you get with a dual delayed timebase with two sweeps and two triggers.

After the first trigger, there is an adjustable delay, and then a second trigger produces the acquisition.  For instance when probing a switching power supply, this allows locking onto the reverse recovery waveform even in the presence of jitter.

In the past this was used to trigger at the start of a video frame, and then select a horizontal line to display with no jitter.  No amount of record length can correctly display that in real time; it requires the second trigger.
--- End quote ---

Of course even the cheap digital scopes have that functionality. On SDS1000X-E it is called interval trigger.

You have one trigger satisfied, then time limit and then when second trigger comes in, you capture the buffer.
--- End quote ---

Usually they have something, but it is not as flexible, and in Rigol's case they outright lied in their documentation deliberately confusing their delayed trigger, which was not even that, with what older oscilloscopes provided with a delayed sweep.


--- Quote ---For video you have video triggers.
--- End quote ---

Old oscilloscopes with video triggering still worked as I described, so their video trigger is not like a modern scope but instead only extracted the video trigger from the video waveform.  Modern instruments with video triggers allow the video line to be selected, although that feature goes back to at least the 1980s so it has been around for a while.  Before that some oscilloscopes provided countdown trigger capability, but I doubt it was ever used for video, although it could have been.

zrq:
I don't want to derail this thread further. I don't really understand, which feature is available on the TBS1000C but not SDS1000X-E ?

Maybe more security of firmware is one example of such a feature, (AFG31000 seems to be based on the same platform, and I'm not sure if it's Secure Boot or some softer checks that maybe bypassed by, for example open case and use JTAG) https://www.eevblog.com/forum/testgear/tektronix-afg-31000-hack/msg3211768/#msg3211768 .

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