Question about analog oscilloscopes vs digital oscilloscopes

[David Hess]

"Slide back" feature of the 7A13 can be found in the modern DSO as DC offset. This is only one of the features of the 7A13, it's real value is as a diff amp with just over 100 Mhz and good common mode at the BNC connectors. A matched pair of Tek P6055 probes were intended for the 7A13 as these probes have adjustable attenuation and HF/LF response to optimize common mode rejection at the probe tip.

DSOs can make calibrated measurements directly so slideback measurements are not necessary although they can be more accurate.  The offset range of most DSOs is a lot less than a 7A13 so I still find a use for it there.

The other place I use slideback measurements is for Gaussian RMS noise both in voltage and time.  High end DSOs can handle this just fine in one way or another and do a better job but they are a lot more expensive.

Origins of the 7A13 goes back to the 1A5 diff plug in (+/- 500 volt common mode range possible) and that plug in has a input specific to the P6046 diff probe.

Here again I only traced the 7A13 back as far as the 3A7.  This information saved me some time so thank you; I have added the 1A5 and 1A7 to my notes now.

On many DSOs you can use split screen (zoom mode) to see a large part and a smaller section of the same signal which basically is equal to what delayed sweep does and having different time bases. I can show the exact same picture of the pulse and the zoomed in section on my DSO.

But they have to work within the limits of their single acquisition record which admittedly is not as much of a problem now because record lengths are so much longer although interface performance suffers.  With delayed sweep (delayed acquisition?), record lengths can be kept short for higher performance while not sacrificing sampling rate.

There is the user interface issue as well.  When we tried to duplicate this kind of capability on a Tektronix MSO5000 series which should have been able to do it, it was both difficult and eventually resulted in an unusable state requiring a reset.  Magnifying just part of the existing acquisition record worked fine if that was all I wanted to do.

[nctnico]

On many DSOs you can use split screen (zoom mode) to see a large part and a smaller section of the same signal which basically is equal to what delayed sweep does and having different time bases. I can show the exact same picture of the pulse and the zoomed in section on my DSO.

But they have to work within the limits of their single acquisition record which admittedly is not as much of a problem now because record lengths are so much longer although interface performance suffers.  With delayed sweep (delayed acquisition?), record lengths can be kept short for higher performance while not sacrificing sampling rate.

Whether or not the UI gets slower depends largely on the oscilloscope's hardware so this is kind of a brand/model specific issue which can be avoided by choosing a different brand/model.

There is the user interface issue as well.  When we tried to duplicate this kind of capability on a Tektronix MSO5000 series which should have been able to do it, it was both difficult and eventually resulted in an unusable state requiring a reset.  Magnifying just part of the existing acquisition record worked fine if that was all I wanted to do.

I still don't understand what you where trying to achieve exactly with the Tektronix MSO5000.

[David Hess]

I still don't understand what you where trying to achieve exactly with the Tektronix MSO5000.

It came down to displaying two different signals with different timebases and different triggers.  I actually wanted to do this with the same signal but it could not do that either or we just could not figure it out.

I spent some time looking through various user manuals for currently produced DSOs and is it my imagination or do most of them lack support for trigger after delay?  I did not find it for the Tektronix MSO2000, Rigol 1000Z, or Rigol 2000A series.  I could not get a manual for the Tektronix MDO3000 or MDO4000 but their discontinued MSO4000 supports it so I am left to conclude that this is now a high end feature.

[nctnico]

My GW Instek GDS2000E series is the only scope I have I know can trigger on different signals with different trigger settings but then again I have not looked for that feature in my other DSOs. The zoom mode (with a split display) can be used for displaying the signals with different timebases.

On a DSO the delayed trigger is 'hidden' in the horizontal position control which allows to scroll the trigger position off screen for pre or post trigger.

[MarkL]

I still don't understand what you where trying to achieve exactly with the Tektronix MSO5000.

It came down to displaying two different signals with different timebases and different triggers.  I actually wanted to do this with the same signal but it could not do that either or we just could not figure it out.

I spent some time looking through various user manuals for currently produced DSOs and is it my imagination or do most of them lack support for trigger after delay?  I did not find it for the Tektronix MSO2000, Rigol 1000Z, or Rigol 2000A series.  I could not get a manual for the Tektronix MDO3000 or MDO4000 but their discontinued MSO4000 supports it so I am left to conclude that this is now a high end feature.

The Tektronix TDS3000 has an A and B trigger, and you can use it to trigger on A and then display the waveform after a trigger on B.  A and B triggers can come from different channels with different slopes and levels.  Optionally, you can also set a time delay after A before B is enabled, or delay B triggering by the number of B trigger events.

The MSO5000 says it has A/B edge triggering on the datasheet.

The Agilent/Keysight DSO/MSO 3000X calls it "Edge then Edge" triggering, but it is the same thing.

The old analog Tek 2465 with the CTT option can do all of the above too, and as a bonus can display the A and B triggered sweeps on the screen at the same time (well, really alternating, but it *looks* like it's at the same time).

I do not see it on the Rigol 1000Z, but I don't think this is a particularly high-end feature.  Your hardware has to have a little extra for the second trigger, so it may not be on the lowest priced scopes.

[David Hess]

The Tektronix TDS3000 has an A and B trigger, and you can use it to trigger on A and then display the waveform after a trigger on B.  A and B triggers can come from different channels with different slopes and levels.  Optionally, you can also set a time delay after A before B is enabled, or delay B triggering by the number of B trigger events.

The MSO5000 says it has A/B edge triggering on the datasheet.

The Agilent/Keysight DSO/MSO 3000X calls it "Edge then Edge" triggering, but it is the same thing.

The old analog Tek 2465 with the CTT option can do all of the above too, and as a bonus can display the A and B triggered sweeps on the screen at the same time (well, really alternating, but it *looks* like it's at the same time).

I do not see it on the Rigol 1000Z, but I don't think this is a particularly high-end feature.  Your hardware has to have a little extra for the second trigger, so it may not be on the lowest priced scopes.

I just took it for granted that low end DSOs which support a delayed sweep (Rigol actually calls it this) would also have a delayed trigger to go with it.  They are rare but there are examples of single timebase analog oscilloscopes which have a delay function like the Tektronix 2213 and 2213A.  I wonder if Rigol's delayed sweep is actually just scaling the original acquisition.

I see now that with their (second?  third?) recent website redesign, Tektronix moved the TDS3000 to the end of their list of DSOs; I thought it was discontinued with the MSO2000 or MSO3000 replacing it.  I still cannot download their current manuals; their web site is broken again reminding me of the MSO5000 user interface.

Almost all of the old analog Tektronix dual delayed timebase oscilloscopes have a B trigger with exceptions like the smaller portables and the T935.  Some always use the A trigger source and others are much more flexible allowing a separate B trigger source like your 2465.

The reason I was looking for the trigger after delay function on these DSOs is that on oscilloscopes which lack alternate triggering, sometimes the B timebase and B trigger can be used to provide almost the same functionality.

[Muxr]

I enjoy using the analog scopes for the haptic feel and nostalgia the same way I enjoy picking up and operating my old OM-2 Olympus film camera. In absence of a DSO an analog scope can still be quite useful. But a DSO is absolutely the way to go if you're in a market for a new scope.

The number of convenient features even the lowest end DSOs have really make a big difference in what you're able to measure quickly.

I would take an analog scope over no scope any day.. but if you gotta have only one scope than DSO is the way to go. Some of us are quite addicted to collecting scopes however, and a collection isn't a collection without at least a few analog scopes

[tggzzz]

Almost all of the old analog Tektronix dual delayed timebase oscilloscopes have a B trigger with exceptions like the smaller portables and the T935.  Some always use the A trigger source and others are much more flexible allowing a separate B trigger source like your 2465.

Not just Tek, of course. Certainly HP had them as well. But then they were aimed at the "high-end" market where you never knew what you would have to do in order to find out what was going on.

Lesser (and cheaper) brands were aimed at markets where the range of tasks was well-defined (e.g. TV, audio), and they often didn't even have a delayed timebase.

[Jwalling]

Yes, I'd be interested in this, thanks

I did have a look through the firmware a while back to see if it could be done this way but I think it would be too time consuming to work out the code changes. The hardware does look to be very similar in the documentation.

I've not taken the covers off it so I don't know how accessible all this stuff is but I really should take it apart to check the PSU caps for leakage etc.
If the upgrade is possible then it would be nice to get the full performance on all 4 channels.

I'm not too worried about bricking it if things go wrong. It didn't cost me anything.

OK, My money would be on R744. Note the bit of dicking about on the solder - it looks like there was a resistor there at one point. R745 also appears to have been removed - not sure about this one. There's only about five resistors with reference designations, the rest have nothing. Very telling, in IMHO.

Messing with these resistors will be more difficult than on the 548XX scopes where all you have to do is remove the cover. You'll have to pull the ACQ board, which is about a 30+ minute job depending on your expertise in this particular scope. IOW a PITA 

EDIT: (trimmed), One thing-  I'm not completely sure this is a 54542A and not a 54540A, but looking at your ACQ board will reveal a difference, hopefully.

Jay

I was wrong about the location. It IS possible, though...
A fellow named Marco on the Agilent groups.io has figured it out. I'd link directly, but if you aren't a subscriber it won't work.
So I'll repost here.

But as but as a little consolation (if you get it running again): If you had a 54540A and a 54542A and compared the two mainboards like I did, you would find that you just have to short the contact pads labeled "R422" to upgrade your scope to a 54542A

A bit of a PITA to do the mod as you will have to pull the acquisition board.