Yet another fast edge pulse generator

[Leo Bodnar]

GET
~IT~
HERE

Do you need a picture to go with that? 

Perfect!

[Howardlong]

Try setting the scope to "talk only" if possible to drive a plotter.

FWIW, that's the way I made it work on an HP 54120B using a Prologix USB GPIB adapter.

As a one-off, I run the GPIB Configurator tool and select the correct COM port, Update the CONFIG.INI, and exit the configurator.

Each time I need to get some screen prints, I run the 7470A emulator (as administrator), select Display->1280x960, select View->Overlay all sources, File->Close all visible plots, and from the Plot menu on the scope I select each of the three plots, one at a time. Once I have the plots, I need I press the space bar to exit the "Listen" mode and I usually use Windows' snipping tool rather than the application to save the bitmap, no particular reason other than that's my workflow.

So in view of the above, more often than not, I just use a camera ;-)

This is Leo's 50ps generator which for some reason performed better today at 54.8ps, but I am sure a lot of that is due to my crappy BNC->SMA transition:


This is the 54121A's TDR pulse viewed on Ch1, the same channel it's generated on, note timebase is now 20ps/div:


The is the same internal TDR pulse viewed on a different channel to where it's generated, i.e. Ch3:

[grumpydoc]

I took the plunge and ordered one on Monday - having finally realised that having the time to build something similar was fantasy 

Hope that it arrives soon.

[Howardlong]

I took the plunge and ordered one on Monday - having finally realised that having the time to build something similar was fantasy 

Hope that it arrives soon.

FWIW, I ordered mine on Saturday and it arrived on Tuesday (UK).

[marshallh]

Working great. Very high quality construction and packaging as well. Pushes the LeCry to 330ps

[orin]

Mine arrived last week after a really good attempt by some postal service or other to squash it...

Here is what my HP 54542A sees.  I have no way of taking screenshots over GPIB from this scope (and don't feel like spending $59 for software that claims to be able to do it*) so it's a cellphone picture.  The scope is set to repetitive with 8 averages.

*no, 7470.exe doesn't work with it.

It should.  I don't have one of those but I've had success reports from at least one other user.  I have a note from another user with a 54502A that says that the listen-only option needs to be selected in 7470.exe's GPIB menu.  Give that a try, maybe, and hit 'w' to make it wait for a plot.  What happens if you press the plot button on the 54542A?

Probably not 7470.exe's fault.  It's probably some 64bit OS/probably fake 82357B/Keysight libraries 488.2 support problem.  'w' gave an immediate error.  I should take the Prologix ethernet adapter home and try it instead.

I think the plot button displayed some message as if it was in progress, then the message went away quietly.  I'd set the GPIB settings on the scope to print to a 7470A at that point.  Even in this state, 'w' in 7470.exe gave an immediate error.

I have had 7470.exe work before on the same PC with the 8568A SA, but I don't recall which adapter I used.

For now, sneaker-net with the floppy drive is working.

It works with the Prologix Ethernet adapter.

Set "No assigned plotter address" on 7470.exe's GPIB menu.
Set the 54542A to talk and select HP 7470.  Disable saving images to disk.
Use the 'w' command on 7470.exe.

Now the Print button on the 54542A does what it should.

[rx8pilot]

I took the plunge and ordered one on Monday - having finally realised that having the time to build something similar was fantasy 

Hope that it arrives soon.

I spent hours researching an approach to build one - probably would have taken another few days to design it, a few days for prototype, another few days for REV B, ........ about a few weeks later, I may or may not have something that worked.

Then I saw this. Lovely. Can't wait to have a play day.

[orin]

Mine arrived last week after a really good attempt by some postal service or other to squash it...

Here is what my HP 54542A sees.  I have no way of taking screenshots over GPIB from this scope (and don't feel like spending $59 for software that claims to be able to do it*) so it's a cellphone picture.  The scope is set to repetitive with 8 averages.

*no, 7470.exe doesn't work with it.

It should.  I don't have one of those but I've had success reports from at least one other user.  I have a note from another user with a 54502A that says that the listen-only option needs to be selected in 7470.exe's GPIB menu.  Give that a try, maybe, and hit 'w' to make it wait for a plot.  What happens if you press the plot button on the 54542A?

For the record, a screenshot of the error I get immediately when using the w command and 82357B/Keysight IO libraries is attached.  I'd have sent it as a PM, but the forum doesn't seem to allow attachments to PMs.

[KE5FX]

Looks good. 

That's a (very) old version of 7470.exe, but given the density and layout of the label text, it might actually look better than the higher-fidelity vector text renderer in the current build.

[orin]

Looks good. 

That's a (very) old version of 7470.exe, but given the density and layout of the label text, it might actually look better than the higher-fidelity vector text renderer in the current build.

It was an old version - I hadn't updated that computer.  I think the file dates were sometime in 2012!

I have now updated that computer and would have to say I prefer the old label text.

[grumpydoc]

Finally arrived   

Very neat gadget.

Some timings to add
LeCroy 9354T (500MHz) - 10Gs/s RIS 660-670ps
Lecroy WavePro 950 (1GHz) - 50Gs/s RIS - 270ps; 16Gs/s single-shot 280ps (no photo for the latter)
Philips/Fluke PM3394A (200MHz) analogue mode 1.72ns
Philips/Fluke PM3394A dgital mode 1.66ns

The Philips needs calibrating as there is a lot of overshoot and ringing.

[alank2]

A question - is it better to look at an equivalent time sample mode or single shot mode for the rise time/fall time measurements?

[Leo Bodnar]

A question - is it better to look at an equivalent time sample mode or single shot mode for the rise time/fall time measurements?

From what I have seen, it looks like different scopes use different strategies and reconstruction filters in both modes.  Single shot mode is typically much more challenging and usually enables sharper roll-off filters that produce more ringing.  On LeCroys equivalent sampling usually shows slightly better risetime results.


I have been playing with various settings and component selection (RF 0201 and 0306 caps) for the pulser and it looks like the best risetime setting is achieved when the output level is set at around 820mV (with 1.000 calibration.)  Actual amplitude as reported  by the scope is 920mV and peak-peak is 976mVpp.  This is including 6% overshoot.  You can match them up by setting calibration adjustment to 1.118 if you want - this does not affect the signal in any way.

Also the pulser fall time is slightly (4-5ps) faster than the rise time.  I can't explain why, probably output stage is marginally better at turning off.

I can't help posting a screenshot from CSA803A - only because standard deviation of risetime measurement is 800 femtoseconds.  Nice, woody word

And yes, 11800/CSA803 user interface is not elegant.

Leo

[Lukas]

Maybe I missed it, but which output driver (the one branded AJK BAA) are you using in the latest revision?

[Leo Bodnar]

Maybe I missed it, but which output driver (the one branded AJK BAA) are you using in the latest revision?

MAX3949

[awallin]

Lecroy WaveSurfer 62MXs-B, 600 MHz, 5GS/s, 50R DC
average rise-time 551.6 ps - no surprises there 
the fall-time was jumping around a lot - may try this again later with more time/care.
more scopes at work to follow - cheerio 

[mweymarn]

Hi,

Received my pulser some time ago. Thanks Leo. Two screenshots attached, using the default settings of the pulser.

First is a Tek TDS7254 (2.5 GHz 20 GS/s), connected via a TCA-BNC adapter.
The second one is a R&S (Hameg) HMO3052 (500 MHz 4 GS/s).

[TheAmmoniacal]

Keysight DSOX1102G, 70 MHz, 1G

4.4 ns rise time.

Micsig MS220T, 200 MHz

1.7 ns rise time.

Tell me if anyone want screenshots.

[alank2]

I received mine today!

Are all the measurements being done here 10%/90% or 20%/80% ?

[TheAmmoniacal]

I received mine today!

Are all the measurements being done here 10%/90% or 20%/80% ?

10%/90% surely?

[Leo Bodnar]

Are all the measurements being done here 10%/90% or 20%/80% ?

There is a long tradition of using 10%-90% when measuring rise time of analogue (asynchronous) signals.

Digital is all messy:
USB 2.0 specify rise time for 10%-90% levels.
PCI Express, HDMI and most logic level specs use 20%-80%.
Maybe it's low voltage swing, maybe improved receivers and reclockers tolerance, maybe it just looks better.

Conversion factor between them for a gaussian response system is about x1.6 which is substantial, so when in doubt - spell it out.

[alank2]

Thanks Leo - pulser works great!!

Rise/fall averaged across all channels.

Pico 2207B (70 MHz): rise=2512, fall=2421 (50 ohm passthrough)
Pico 2407B (70 MHz): rise=2686, fall=2564 (50 ohm passthrough)
HP 54645D (100 MHz): rise=2375, fall=2375 (50 ohm passthrough)
BK 2120 (20 Mhz): rise=20000 (50 ohm passthrough, it was 2/5 of a graduation where the graduation was 50nS)
Rigol DS2072 (300 MHz): rise=980, fall=994 (50 ohm passthrough)
Rigol DS4014 (500 MHz): rise=653, fall=647 (50 ohm built-in)

[richnormand]

Got mine today. Nice packing job, perfect. Thanks Leo.  Love the trig output.

As stated in my earlier post here I wanted to check my old Tek S6 sampling head after changing a sampling-and-hold Tek opamp with a generic one. I am using a 7s12 TDR plugin with a s-53 trigger recogniser for this measurement.

Using the 10-90% I got about 58ps rise-time. As 100% I used the high level after the ringing stopped. I also assumed the pulser supplied trace showing a rise-time of 49.2ps for the unit as correct as I do not know the specs of the measuring instrument. I assume it is much better than my old stuff If true, that gives me 30.7ps for the S-6 unit using the usual the t^2 sum equation. It's specifications are 30ps rise-time.

Not bad considering how old it is!

Next step will be to test my R7912 transient digitizer for its single shot 1GHz bandwidth.

[Leo Bodnar]

I also assumed the pulser supplied trace showing a rise-time of 49.2ps for the unit as correct as I do not know the specs of the measuring instrument. I assume it is much better than my old stuff

I have two CSA803A in very good condition, looking almost brand new inside and a variety of sampling heads, one SD-30 (40GHz) and a number of SD-26(20GHz) and SD-22(12.5GHz.)
They are all from different sources and I have cross-checked them against each other - they all agree within noise floor limits. 
This is old equipment from 1990's so it hardly makes any sense to get calibrated, especially for the fun project like this.

I use CSA803A with SD-26 head (17.5ps nominal risetime) installed to print the slips I include with each pulser I send away.
I have tested few units on SD-30 (8.8ps risetime) and there is only 2-3ps difference in the total result - as expected.

Overall I am quite happy with the pulser design performance so will leave it as it is for now.

Leo

[richnormand]

Thanks for the trace information Leo. 

The risetime numbers do make sense then, even if I shave a few ps to deconvolve your trace.... well within experimental error.

""Overall I am quite happy with the pulser design performance so will leave it as it is for now.""
Agreed! The unit is a very nice piece of work, don't mess with greatness.

I believe my S-6 sampling head with about 10GHz bandwidth is circa 1970s vintage so your equipment is positively modern by my standards

Can't wait to see what you come up with as an encore.

Cheers and thanks.

rich