Author Topic: Yet another fast edge pulse generator  (Read 58936 times)

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Online lukier

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Re: Yet another fast edge pulse generator
« Reply #150 on: August 02, 2017, 05:19:09 am »
You need to adjust the vertical gain so that the square wave top is at the solid line above the top dotted line, and the square wave bottom is at the solid line below the lower dotted line. Then the two dotted lines will be at 10% and 90%. Set the two cursors where the trace crosses the 10% and 90% dotted lines.

His measurement is correct. Waveform's top and bottom should be on the dotted lines(!) and then the next solid line is the 10% and 90%. This is even marked on the overlay in the photo.
 
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Offline Tom45

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Re: Yet another fast edge pulse generator
« Reply #151 on: August 02, 2017, 06:36:35 am »
You need to adjust the vertical gain so that the square wave top is at the solid line above the top dotted line, and the square wave bottom is at the solid line below the lower dotted line. Then the two dotted lines will be at 10% and 90%. Set the two cursors where the trace crosses the 10% and 90% dotted lines.

His measurement is correct. Waveform's top and bottom should be on the dotted lines(!) and then the next solid line is the 10% and 90%. This is even marked on the overlay in the photo.

You are right!  The few times I've ever needed to measure rise time I never bothered to look at the scale. I just went with my faulty memory of what I once knew.   Thanks for setting me straight.

Now I need to go back and redo my Tek analog scope measurements.

Tom
 

Offline WastelandTek

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Re: Yet another fast edge pulse generator
« Reply #152 on: August 02, 2017, 07:12:27 am »

You are right!  The few times I've ever needed to measure rise time I never bothered to look at the scale. I just went with my faulty memory of what I once knew.   Thanks for setting me straight.

Now I need to go back and redo my Tek analog scope measurements.

Tom

This....is what I absolutely love about this forum.  I have seen it several times in the short period I have been a member; someone say, in essence "oh god, you're right, I was mistaken"  this is a rare thing on the internet and to be applauded IMO.

Leo seems to have done an outstanding job on this pulser, looking forward to getting one.
I'm new here, but I tend to be pretty gregarious, so if I'm out of my lane please call me out.
 

Offline bson

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Re: Yet another fast edge pulse generator
« Reply #153 on: August 02, 2017, 07:47:19 am »
Still making these?  I missed the thread initially but would love to buy one!
 

Offline Leo Bodnar

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Re: Yet another fast edge pulse generator
« Reply #154 on: August 02, 2017, 07:55:25 am »
Still making these?  I missed the thread initially but would love to buy one!
Sure, I have them in stock.

Get yours here.

Thanks
Leo

Offline Tom45

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Re: Yet another fast edge pulse generator
« Reply #155 on: August 02, 2017, 08:03:44 am »
Still making these?  I missed the thread initially but would love to buy one!

Leo has a business designing and selling items such as this pulse generator. So it should be available long term which benefits all of us.

http://www.leobodnar.com/shop/index.php?main_page=product_info&cPath=124&products_id=295
 

Offline Gixy

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Re: Yet another fast edge pulse generator
« Reply #156 on: August 02, 2017, 09:17:14 am »
Another good old analog scope: HP 1742A, 100MHz, 50 Ohm. Rise & Fall times: 3.5ns.

It is generally admitted to use 0.35 (0.356 indeed) for scopes with BW lower than 1GHz and 0,45 for the others.
 

Offline alank2

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Re: Yet another fast edge pulse generator
« Reply #157 on: August 02, 2017, 09:40:00 am »
I ordered one - really looking forward to it!
 

Offline electrolust

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Re: Yet another fast edge pulse generator
« Reply #158 on: August 03, 2017, 12:24:31 am »
Received mine via the slow boat ... works great.  I won't bother to post results, they are like everyone else's here.  But I do want to comment on how professionally made and packed the device was.  Wow!
 

Offline rx8pilot

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Re: Yet another fast edge pulse generator
« Reply #159 on: August 03, 2017, 03:11:07 am »
But I do want to comment on how professionally made and packed the device was.  Wow!

Totally. Super sharp.
Factory400 - the worlds smallest factory. http://www.youtube.com/c/Factory400
 

Offline orin

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Re: Yet another fast edge pulse generator
« Reply #160 on: August 03, 2017, 03:11:43 am »
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.
 

Offline electrolust

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Re: Yet another fast edge pulse generator
« Reply #161 on: August 03, 2017, 04:43:49 am »
Question: Is the overshoot actually there, or it is an artifact of sin(x)/x interpolation?  If it's actually there, is it part of the output or is that a byproduct of the [short] transmission line / PCB trace / etc.
 

Offline branadic

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Re: Yet another fast edge pulse generator
« Reply #162 on: August 03, 2017, 04:49:16 am »
Quote
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.

If your unit has RS232 interface available you can simply read data via RS232-USB-adapter using any terminal program such as hterm. I would recommand using gnu octave, it just takes a few commands to aquire data and plot them also live.

-branadic-
Prema 5000 | 2x Prema 5017 SC | GenRad 1434-G | Tek 2465A | VNWA2.x with TCXO upgrade and access to: Keysight 3458A, Keithley 2002, Prema 5017 SC, 34401A, 34410A, Keithley 2182A, HDO6054, Keysight 53230A and other goodies at work
 

Offline HighVoltage

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Re: Yet another fast edge pulse generator
« Reply #163 on: August 03, 2017, 05:08:53 am »
I was surprised that the measured rise time of the Keysight MSO-X-6104A from rx8pilot was significantly faster than mine.
He measured 70 ps and my instrument had measured 88 ps

So, I measured all my 4 channels again:

Scope-Channel, t-rise, Overshoot
CH 1,  88.6,   6.3%
CH 2,  87.9,   6.8%
CH 3,  82.7,   9.8%
CH 4,  83.2,   8.6%

Still about 12 to 18 ps slower than the rx8pilot data.
May be it is related to the overshoot.

Leo Bodnar:
I would like to buy another pulser from you but I would like you to make sure it has the smallest possible overshoot, like in the picture from rx8pilot or even less.
Is that possible that you pre-select one?

Or what do you think is the difference between the measurements of these two scopes?




« Last Edit: August 03, 2017, 05:13:28 am by HighVoltage »
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Offline Leo Bodnar

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Re: Yet another fast edge pulse generator
« Reply #164 on: August 03, 2017, 05:21:18 am »
I would like to buy another pulser from you but I would like you to make sure it has the smallest possible overshoot, like in the picture from rx8pilot or even less.
Is that possible that you pre-select one?
All units are quite consistent in their parameters - within 1-2% overshoot and ±4ps risetime.
I can try critically damping the output to have no overshoot - it will increase the risetime by ~10ps.
I am going to make another batch tomorrow or on Friday and will try tweaking one unit.
At the moment I only have 20GHz SD-26, 12.5GHz SD-22 and 3GHz WavePro 7300A to go by.
Leo

Online lukier

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Re: Yet another fast edge pulse generator
« Reply #165 on: August 03, 2017, 05:33:21 am »
Question: Is the overshoot actually there, or it is an artifact of sin(x)/x interpolation?  If it's actually there, is it part of the output or is that a byproduct of the [short] transmission line / PCB trace / etc.

My LeCroy WaveRunner 6100A (1 GHz) screenshot was without sin(x)/x. I can redo the measurement with sin(x)/x turned on and we'll see the difference.
 

Offline HighVoltage

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Re: Yet another fast edge pulse generator
« Reply #166 on: August 03, 2017, 06:10:43 am »
I would like to buy another pulser from you but I would like you to make sure it has the smallest possible overshoot, like in the picture from rx8pilot or even less.
Is that possible that you pre-select one?
All units are quite consistent in their parameters - within 1-2% overshoot and ±4ps risetime.
I can try critically damping the output to have no overshoot - it will increase the risetime by ~10ps.
I am going to make another batch tomorrow or on Friday and will try tweaking one unit.
At the moment I only have 20GHz SD-26, 12.5GHz SD-22 and 3GHz WavePro 7300A to go by.
Leo

Then it seems I was wrong and want the opposite.
I want the fastest possible rise time, so I need a larger overshoot?
Can you tweak that too?

In a way to match the one from rx8pilot
Here is his picture again:

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Offline WastelandTek

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Re: Yet another fast edge pulse generator
« Reply #167 on: August 03, 2017, 06:28:42 am »

At the moment I only have 20GHz SD-26, 12.5GHz SD-22 and 3GHz WavePro 7300A to go by.
Leo

"only"   ;D
I'm new here, but I tend to be pretty gregarious, so if I'm out of my lane please call me out.
 
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Offline Howardlong

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Re: Yet another fast edge pulse generator
« Reply #168 on: August 03, 2017, 07:17:23 am »
I don't have an msox6000 series, but I'd assume there's a way to change to equivalent time sampling as there is on the mso7000 where it's in the Acquire menu. Switching to equivalent time on my mso7104b and 54831d (masquerading as a 54832d) significantly improves rise time figures, I assume because of sampling aliasing errors in real time mode, but I wouldn't be surprised if the filtering may be changed somewhat too.

This ties into the overshoot that brick wall filters typically create, employed in real time sampling especially at higher speeds closer to the sampling rate, in an effort to avoiding aliasing problems. More gentle Gaussian filters avoid the overshoot but are more prone to aliasing: it's good old fashioned engineering compromise at work. It's also why the rise time/bandwidth calculation fudge factor changes.

There are a number of Keysight docs on the phenomenon, for example http://literature.cdn.keysight.com/litweb/pdf/5988-8008EN.pdf

« Last Edit: August 03, 2017, 07:56:59 am by Howardlong »
 

Offline HighVoltage

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Re: Yet another fast edge pulse generator
« Reply #169 on: August 03, 2017, 08:06:52 am »
I don't have an msox6000 series, but I'd assume there's a way to change to equivalent time sampling as there is on the mso7000 where it's in the Acquire menu. Switching to equivalent time on my mso7104b and 54831d (masquerading as a 54832d) significantly improves rise time figures, I assume because of sampling aliasing errors in real time mode, but I wouldn't be surprised if the filtering may be changed somewhat too.

This ties into the overshoot that brick wall filters typically create, employed in real time sampling especially at higher speeds closer to the sampling rate, in an effort to avoiding aliasing problems. More gentle Gaussian filters avoid the overshoot but are more prone to aliasing: it's good old fashioned engineering compromise at work. It's also why the rise time/bandwidth calculation fudge factor changes.

There are a number of Keysight docs on the phenomenon, for example http://literature.cdn.keysight.com/litweb/pdf/5988-8008EN.pdf

Yes, there is a similar menu in the 6000X scope

I tried following Data Acquisition Modes:
- Realtime = 88,5 ps
- Realtime (Max Update Rate) = 88,5 ps
- Equivalent time = 89.4 ps

I also tried the different acquisition modes:
- Normal
- Peak detect
- Averaging
- High Resolution
But the rise time will always be around 88ps, compared to rx8pilot's 70 ps.

Thanks for the link to the Keysight doc, I will study it.





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Offline Cerebus

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Re: Yet another fast edge pulse generator
« Reply #170 on: August 03, 2017, 09:57:20 am »
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Offline orin

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Re: Yet another fast edge pulse generator
« Reply #171 on: August 03, 2017, 12:09:59 pm »
Quote
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.

If your unit has RS232 interface available you can simply read data via RS232-USB-adapter using any terminal program such as hterm. I would recommand using gnu octave, it just takes a few commands to aquire data and plot them also live.

-branadic-


Thanks for the hint.

I had totally forgotten that this puppy has a floppy drive.  If the drive is working...

So, I found a suitable floppy, found the disk menu, saved the image in TIFF format, read it in using an external USB drive on the Mac, converted it to PNG and uploaded it.

This image is while the scope is still building up the trace in repetitive mode.  No connecting of the dots at this point.  It sure shows that the overshoot is real on this scope.

I found the scope's spec and rise time is spec'd at 700ps.  I guess 475ps is quite acceptable!

Edit: The 1.333ns max rise time isn't real - it's an artifact of how the repetitive sampling works.
« Last Edit: August 03, 2017, 12:17:17 pm by orin »
 

Offline alank2

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Re: Yet another fast edge pulse generator
« Reply #172 on: August 03, 2017, 12:36:16 pm »
What is the calibration adjustment for?  The peak to peak voltage output?
 

Offline KE5FX

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Re: Yet another fast edge pulse generator
« Reply #173 on: August 03, 2017, 02:51:56 pm »
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? 
 

Offline orin

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Re: Yet another fast edge pulse generator
« Reply #174 on: August 03, 2017, 05:16:26 pm »
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.
 


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