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Offline Electro Fan

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40 ps Rise Time
« on: May 07, 2016, 11:02:23 AM »
A new PR (personal record) as they say in track and field:  a rise time measurement of about 40 picoseconds (40 trillionths of a second).  This is slightly more than a 6x improvement over the previous PR of about 250 picoseconds (ie, about a quarter of a nanosecond which is of course a quarter of a billionth of a second). 

In the image you can see that the voltage increases about 200 mV (4 vertical divisions upward at 50mV per division from the 10% line to the 90% line) in about 2 horizontal divisions (each horizontal division being 20 picoseconds) for a total elapsed time of approximately 40 picoseconds.  I don't see any good way to get to a sub picosecond (less than a trillionth of a second) rise time, but it might be possible to squeeze out another 5 - 10 picoseconds with some further studying and fine tuning.

It would take 25 billion of these 40 picosecond increments to move a watch needle 1 second.

No big deal for the veterans here I realize but kind of fun for a guy who had not much of a clue about pulse generators and rise time measurements a couple years ago. :)
« Last Edit: May 07, 2016, 11:06:44 AM by Electro Fan »
 
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Offline joeqsmith

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Re: 40 ps Rise Time
« Reply #1 on: May 07, 2016, 11:07:56 AM »
Nice job!
How electrically robust is your meter?? http://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 

Offline JuiceKing

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Re: 40 ps Rise Time
« Reply #2 on: May 07, 2016, 11:34:51 AM »
Awesome! You beat my record by 16ps!

What is your source? Which mainframe are you using?

- Ken
 

Offline Electro Fan

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Re: 40 ps Rise Time
« Reply #3 on: May 07, 2016, 12:19:56 PM »
Nice job!

Thanks, your earlier work was in part what inspired me!
 

Offline Electro Fan

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Re: 40 ps Rise Time
« Reply #4 on: May 07, 2016, 12:25:30 PM »
Awesome! You beat my record by 16ps!

What is your source? Which mainframe are you using?

- Ken

Thanks.  I'm using a 7904 with a S-52 and a S-6 in a 7S12.  I still have some things to figure out and better understand about the various Tektronix parts.  It's a journey.
 

Offline AF6LJ

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Re: 40 ps Rise Time
« Reply #5 on: May 07, 2016, 12:30:34 PM »
This is too cool.
Great Job.
I would love to see the circuit and your layout technique.
Sue AF6LJ
Test Equipment Addict, And Proud Of It.
 

Offline Electro Fan

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Re: 40 ps Rise Time
« Reply #6 on: May 07, 2016, 02:03:28 PM »
This is too cool.
Great Job.
I would love to see the circuit and your layout technique.

Pretty simple - plug n play with off the shelf Tektronix everything, if you can find the parts in working condition.

The S-52 pulse generator and the S-6 sampling head sit inside a 7S12 plugin which sits inside the 7904 mainframe.

The S-52 is connected to the S-6 with a short SMA to SMA rigid jumper cable.  The 7S12 has a dual dial that lets you choose time divisions plus a 10x, 1x and 0.1x setting and it also has a TDR function that allows you to scroll around in the time domain as well as measure time delays and correlate time to cable lengths.  You just plug it all together as described and twiddle the dials and the pulse generated by the S-52 appears on the display as shown.  You can find old scanned user manuals in pdf formats on the web.  Other than reading the manuals the primary skill required has more do with hunting for antiques than electrical engineering but when you get the parts found and working you have some very good measuring capabilities.
« Last Edit: May 07, 2016, 02:06:55 PM by Electro Fan »
 
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Offline Howardlong

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Re: 40 ps Rise Time
« Reply #7 on: May 07, 2016, 04:23:26 PM »
Niiiice!

I don't know what's so fascinating about this, but it floats my boat: a good day I can get a tad over 30ps out of my 54121T boat anchor setup.

 

Offline Electro Fan

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Re: 40 ps Rise Time
« Reply #8 on: May 07, 2016, 05:38:59 PM »
Niiiice!

I don't know what's so fascinating about this, but it floats my boat: a good day I can get a tad over 30ps out of my 54121T boat anchor setup.



Yep, there is something hard to describe at work in getting these measurements - I think part of it is just the notion of measuring things in billionths and trillionths - not to mention it's billionths and trillionths of something already kind of small (1 second).  You and Joe might be the leaders in the eevblog forum fastest rise times sweepstakes. :)
 

Offline Earendil

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Re: 40 ps Rise Time
« Reply #9 on: May 07, 2016, 08:22:26 PM »
I'll play too.
20ps/div. Rise time 25.6ps.
 

Online Fungus

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Re: 40 ps Rise Time
« Reply #10 on: May 07, 2016, 08:47:12 PM »
What about fall times?  :box:
 
 

Offline alsetalokin4017

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Re: 40 ps Rise Time
« Reply #11 on: May 07, 2016, 08:53:39 PM »
I'll play too.
20ps/div. Rise time 25.6ps.
Check your workbench -- your oscilloscope has fallen over onto its side.
The easiest person to fool is yourself. -- Richard Feynman
 

Offline EV

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Re: 40 ps Rise Time
« Reply #12 on: May 07, 2016, 08:54:32 PM »
I take part also!
 

Online Fungus

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Re: 40 ps Rise Time
« Reply #13 on: May 07, 2016, 08:57:00 PM »
I'll play too.
20ps/div. Rise time 25.6ps.
Check your workbench -- your oscilloscope has fallen over onto its side.

I thought he was using a grey-import camera or something - wrong latitude for his country.

 

Offline Earendil

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Re: 40 ps Rise Time
« Reply #14 on: May 07, 2016, 08:58:48 PM »
No, no. That's intentional. It makes the electrons go faster.  :-DD
I'll play too.
20ps/div. Rise time 25.6ps.
Check your workbench -- your oscilloscope has fallen over onto its side.
 

Offline Earendil

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Re: 40 ps Rise Time
« Reply #15 on: May 07, 2016, 09:38:06 PM »
I take part also!
Thanks for posting this.
Did you do anything special to achieve such a fast rise time with the Tek S-4?
According to the TekWiki site (http://w140.com/tekwiki/wiki/S-4) it "only" has 25ps rise time.
 

Offline EV

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Re: 40 ps Rise Time
« Reply #16 on: May 07, 2016, 10:15:18 PM »
..
Did you do anything special to achieve such a fast rise time with the Tek S-4?
..

The s-4 head is connected directly to Tek 284 pulse generator connector with 3 FT long SAMPLING HEAD EXTENDER. There was nothing else special. The used plug ins are 7S11 and 7T11.
« Last Edit: May 07, 2016, 10:18:55 PM by EV »
 
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Offline Electro Fan

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Re: 40 ps Rise Time
« Reply #17 on: May 08, 2016, 01:56:18 AM »
 

Offline max-bit

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Re: 40 ps Rise Time
« Reply #18 on: May 08, 2016, 05:48:29 AM »
Someone shared schema pulse generator so fast pulse?
 

Offline Howardlong

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Re: 40 ps Rise Time
« Reply #19 on: May 08, 2016, 06:17:13 AM »
I take part also!

Very nice! You need to work on that jitter though ;-)

A vid of how this works in the Tek world would be great. The HP I have doesn't do the random equivalent time sampling that I believe the Teks do so there's some jiggery pokery that you need to do particularly if the signal's not regular or not reasonably repetitive.

FWIW I did a couple of vids on the HP setup referenced in the square wave thread. http://www.eevblog.com/forum/testgear/show-us-your-square-wave/msg863872/#msg863872

 

Offline Earendil

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Re: 40 ps Rise Time
« Reply #20 on: May 08, 2016, 06:32:55 AM »
I'm not sure about the older Tekronix sampling scopes but I don't believe the 11800 series does random equivalent time sampling.
I kind of remember reading in some Tek document that random equivalent time sampling is somewhat limited in performance.
 

Offline Earendil

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Re: 40 ps Rise Time
« Reply #21 on: May 08, 2016, 06:45:15 AM »
From Tekronix XYZs of Oscilloscopes:
"The bandwidth limit for random equivalent-time sampling is less than for sequential-time sampling."
Unfortunately it doesn't go into details.

Edit: It adds the following:
"Technologically speaking, it is easier to generate a very short,
very precise “delta t” than it is to accurately measure the
vertical and horizontal positions of a sample relative to the
trigger point, as required by random samplers. This precisely
measured delay is what gives sequential samplers their
unmatched time resolution."
« Last Edit: May 08, 2016, 06:48:14 AM by Earendil »
 

Offline Howardlong

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Re: 40 ps Rise Time
« Reply #22 on: May 08, 2016, 07:21:19 AM »
Ok, thanks for that, I wasn't aware that there was a technical performance limitation, but happy to have learned something new.
 

Offline Electro Fan

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Re: 40 ps Rise Time
« Reply #23 on: May 09, 2016, 09:34:59 AM »
Just checking to see if anyone has some advice on how to adjust the Horizontal SWEEP CAL Control on the 7S12?  I have things finally running with the various plug ins :phew: and I'm somewhat reluctant to twiddle more controls.

In the 7S12 manual it shows a waveform as in the graphic attached below.  Any chance that with a timebase setting of 1us that pulse #1 should be 1 division across (1 us), and the inverted pulse #2 should be about a half a division across (0.5 us)?

I can come of course up with a tool to make the adjustment but I'm wondering what the best way is to get it calibrated properly?

Thanks!
« Last Edit: May 09, 2016, 09:37:53 AM by Electro Fan »
 

Offline joeqsmith

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Re: 40 ps Rise Time
« Reply #24 on: May 09, 2016, 09:17:20 PM »
Some time ago I had posted in a single transistor oscillator thread where I was attempting to run at some higher frequencies than had previously been shown.  Finger tight and the front connector is not locked down. 

This is about the fastest edge I can get with a scope.    The fastest oscillator I cobbled up ran a little over 10G but beside my antique spectrum analyzer and counter, I have no way to display the data.   
How electrically robust is your meter?? http://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
 


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