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It's meant as a loop through, which is why there is no internal 50 ohm load.

Harvey

Thanks for the endorsement Raymond. Coming from you makes me feel like I might actually be starting to get this stuff.

Stephen, I've been studying the 7S12/S-52 documentation PDFs since the May. I feel I'm _just_ beginning to grasp the 7S12 TDR functional diagrams. See Figures 3-4 and 3-5 from the 7S12 PDFs on the TekWiki. I'm still not quite there myself. I can't even form the right questions yet: like how do the fast ramp and slow ramp interact? I'm still working on it. But from what I understand: the S-52 has a logic state machine that produces the "trigger". This pulse goes into the 7S12 which delays it, sends it back to the S-52 to fire the tunnel diode, and sends the appropriate horizontal signals to the mainframe - sweep start, blanking, etc. Again, I'm still just now starting to sort that out.

I had the same questions, and just acquired a S-53 to enable use of the 7S12 as a sampling scope. Give yourself some time. This stuff is complicated.

Dave

On Fri, Dec 24, 2021 at 07:13 PM, Dave Peterson wrote:

Stephen, I've been studying the 7S12/S-52 documentation PDFs since the May. I
feel I'm _just_ beginning to grasp the 7S12 TDR functional diagrams. See
Figures 3-4 and 3-5 from the 7S12 PDFs on the TekWiki. I'm still not quite
there myself. I can't even form the right questions yet: like how do the fast
ramp and slow ramp interact? I'm still working on it. But from what I
understand: the S-52 has a logic state machine that produces the "trigger".
This pulse goes into the 7S12 which delays it, sends it back to the S-52 to
fire the tunnel diode, and sends the appropriate horizontal signals to the
mainframe - sweep start, blanking, etc. Again, I'm still just now starting to
sort that out.

It's important to realize that you need to know only very little about the 7S12, S-6 and S-52's precise functioning to be able to use the unit. Basically, it's just another standard TDR setup, using a generator producing a fast pulse, sending that pulse into a transmission line and watching what comes back.
Alan Wolke made a very nice video on Youtube about it, as have many others.
You need to have some knowledge about what happens if a signal goes through a transmission line that changes its impedance in some particular location.
Once you get the basic idea, it's quite nice and very enlightening to play with this tool.

Raymond

Ok. Thanks all. I will review as much material as I can. Happy to know that the unit is working as it should, and at some point it was properly calibrated, has the cal seals intact, albeit from 20 years ago. But still, I’m not gonna mess with the calibration.

MERRY CHRISTMAS TO YOU ALL.

Commenting on your photos is not easy because we don't see the whole story.

The V-A, H-B picture showing the pulser output looks like what I would expect.

On the "20 mV 50 ps" picture with the fast rising edge, your vertical setting is too sensitive to see the entire reflection.
You want to see the baseline on the left, the middle trace corresponding to the short 50 ohm line segment from the sampling point to the unterminated SMA output on the S-6 (and back) at the S-52's rated 200 mV into 50 Ohms, then the second step showing the unterminated end where the voltage goes up to 400 mV.

BTW, the 7S12 really needs to be properly warmed up.

Take a look at to see a 7S12 used on a real-world problem, with some helpful comment.

I wouldn't have much respect for the 20 year old cal stickers. The key parameters - vertical gain, sweep - are calibrated "in action" via front panel trims.

Merry Christmas!

I understand Peter.
I’ll try to have some more available when I have more time.
Right now I’m fixing my 7623.

Thanks again.

I don’t yet know how to interpret these, but I made 4 more pictures that vaguely resemble the ones Miguel uploaded earlier.

Cable is a 6” 50Ω load and SMA to BNC adaptors. Nothing fancy.

Experts, what do you say?

Cheers

/g/TekScopes/album?id=270997

On Sun, Dec 26, 2021 at 11:12 PM, Stephen wrote:

Experts, what do you say?

Hey Stephen,
Why don't you read up on the basics, indicated and described by several on this Group in this thread. Pointers like general TDR principles, ideas and setups, Alan Wolke (W2AEW)'s videos on Youtube? Very little study of your 7S12 needed at first.

Raymond

On Mon, Dec 27, 2021 at 01:17 PM, Raymond Domp Frank wrote:

Alan Wolke (W2AEW)'s videos on Youtube?

This is a very clear, informative and easy to understand video (as always with Alan). It makes you aware of what to expect and how to get there.



Raymond

On Sun, Dec 26, 2021 at 11:12 PM, Stephen wrote:

I don’t yet know how to interpret these,

Not much to interpret in terms of TDR in your pictures.
Remember, a TDR shows impedance *discontinuities*. If you connect everything nicely terminated, there won't be much to see.

Read your manual for basic operation and setup of your 7S12. Peter H recently correctly mentioned that your vertical sensitivity was set too high. In addition, you need to realize that you have to connect the cable that you want to look at to the S-6's second port and *not* terminate it (at first), or you won't see an echo because there's "no" impedance jump. Set horizontal speed (50ps/div in your pictures) to one that is slow enough to bridge double the propagation time in your cable, or you won't see the echo. Again, Alan Wolke explains what's happening very well and your 7S12 isn't much more than a dedicated 'scope (setup).
Once you get a little further, use a fast horizontal speed to find the "reference plane", i.e. the propagation-time location where the open port of the S-6 sits. The S-52's pulse reflects there because that S-6 port is open, either directly at the port or, preferably, at the end of a short "SMA-save" cable or connector. Any connected cable length will be added to that reference location. It's all in the basic operation info.
But make sure you first understand what's going on in general and thereby, what to look for and what to expect.

Raymond