Author Topic: impedance measurement with VNA using series, shunt/series through methods, graph  (Read 9866 times)

0 Members and 1 Guest are viewing this topic.

Online joeqsmith

  • Super Contributor
  • ***
  • Posts: 8351
  • Country: us
The last set of cores arrived.  From 10KHz to 1MHz, the home made transformer has higher common mode attenuation than the PICO.   Adding one or two more turns would certainly help the low frequency performance but it hurts the insertion loss.    I suspect with the materials used, the home made transformer would out perform the PICO below 10KHz.   

The home made transformer's insertion loss is about 0.5-1dB worse at 6GHz.   Picotest's site claims "Maintains 50 Ohm transmission line integrity to at least 6GHz".   Shown with data plotted up to 8GHz.   
 

 
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
Software, documentation and test reports for the low cost NanoVNA & V2 Plus 4 may be found here:
https://github.com/joeqsmith
 

Online joeqsmith

  • Super Contributor
  • ***
  • Posts: 8351
  • Country: us
I am not sure why the Picotest transformer has such a mismatch but we can use the frequency between the peaks to determine the length of the cable.  We can also take a guess at the cable type based on the loss.   The match appears to be better with the home made transformers.   Possibly due to higher quality cable and connectors.   

To give you some idea on the price,  the majority of the cost of these two transformers was the connectors.  The nanocrystalline cores came next, followed by the box, then the Mn-Zn cores, hardware and coax.    The transformer on the right was about $200, more than half of that was connectors.   
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
Software, documentation and test reports for the low cost NanoVNA & V2 Plus 4 may be found here:
https://github.com/joeqsmith
 

Online JohnG

  • Frequent Contributor
  • **
  • Posts: 401
  • Country: us
These are interesting results, but I am a bit confused. How exactly is CM attenuation being measured? I looked back through this thread, but never found a very clear definition. In addition, it seems as if this would be dependent on the measurement instrument, since this would determine the alternate ground path that is responsible for the CM signal, but it looks like the Picotest and hand-made transformers are measured on different instruments. If so, then a close comparison loses some meaning. Please correct me if I'm mistaken.

It seems to me that a direct measure of the transformer common-mode inductance might be more repeatable, at least at low frequency. Or, is this what is actually being done and I missed the steps?

Cheers,
John
"Those who learn the lessons of history are doomed to know when they are repeating the mistakes of the past." Putt's Law of History
 

Online joeqsmith

  • Super Contributor
  • ***
  • Posts: 8351
  • Country: us
These are interesting results, but I am a bit confused. How exactly is CM attenuation being measured? I looked back through this thread, but never found a very clear definition. In addition, it seems as if this would be dependent on the measurement instrument, since this would determine the alternate ground path that is responsible for the CM signal, but it looks like the Picotest and hand-made transformers are measured on different instruments. If so, then a close comparison loses some meaning. Please correct me if I'm mistaken.

It seems to me that a direct measure of the transformer common-mode inductance might be more repeatable, at least at low frequency. Or, is this what is actually being done and I missed the steps?

Cheers,
John

I'm not at all surprised by your confusion as I am still not clear about it myself.    As I understand it, three different VNAs were used following two different methods.  If we include insertion loss, I suspect five different VNAs were used.   ***  I used a one to measure common mode and another for insertion.  The Bode 100 is certainly not up to measuring 6GHz so we expect Picotest used a second VNA as well.   

Here we can see a picture of Brian's setup.   He works for Copper Mountain, so no surprise, is using one of their VNAs to perform the measurement.
https://www.eevblog.com/forum/rf-microwave/impedance-measurement-with-vna-using-series-shuntseries-through-methods/msg3554237/#msg3554237

Of course when we compare Brian's results with what Picotest has published, they are very different.
https://www.eevblog.com/forum/rf-microwave/impedance-measurement-with-vna-using-series-shuntseries-through-methods/msg3548742/#msg3548742

I wrote Picotest to try and understand how they conducted the test.   While their response makes sense, I don't believe it was the cause of the difference.  They are using the Bode 100 but it shouldn't matter.   Something else is off and I am not sure what.   I suspect it gets back my mom drowning all her dumb kids.  A bit of a smoke screen if you will.   I see this with other papers they have published where details are missing.  Just part of the business model I guess.

https://www.eevblog.com/forum/rf-microwave/impedance-measurement-with-vna-using-series-shuntseries-through-methods/msg3561853/#msg3561853

You could see in that last post my attempt to replicate what Picotest explained.  I saw no difference between this method and what Brian showed.  I wasn't expecting to.    Brian's VNA is limited to about 9KHz where I can run down to 10Hz.   For the S21 plots where I overlay Brian's results with my own, I am attempting to run the same setup.  I would expect the results to be very similar. 

I have included a few pictures of the log sweeps down to 10Hz to provide viewers with more detail on how my transformers performed.

For insertion loss, I would expect Brian just calibrated the VNA and placed it between the two ports which is what I am doing. 
« Last Edit: May 21, 2021, 06:45:16 pm by joeqsmith »
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
Software, documentation and test reports for the low cost NanoVNA & V2 Plus 4 may be found here:
https://github.com/joeqsmith
 

Online JohnG

  • Frequent Contributor
  • **
  • Posts: 401
  • Country: us
I don't see any issues with insertion loss, since that should be more straightforward both to measure and to calibrate out.

But, I think that CM attenuation of a given transformer can really only be compared if the systems are the same, because it will depend on the impedance of the instrument ground path relative to the cable ground path, and this is really unlikely to be the same. However, the measurement description sounds more like a straight attenuation measurement, as if you sent a test signal through an inductor and looked at each of its terminals. In that sense, it should be basically valid at lower frequencies, but it's not really CM attenuation in a well defined sense, even if it correlates well. At high frequencies, you would at least want a fixture, same cables, etc.

Also at high frequencies (upper 10s of MHz and up), you would need to be very careful about intrawinding capacitance as you will get capacitive coupling between turns and this will lower the CM impedance. MgZn cores are a problem in this regard as they are not really a very good dielectric even at DC, and they get worse at high frequencies. NiZn cores are usually much better for this, though it can work with MgZn cores if you space the windings from the core. In either case, and make sure not to overlap windings and keep a sizable gap between the end turns.

Cheers,
John
"Those who learn the lessons of history are doomed to know when they are repeating the mistakes of the past." Putt's Law of History
 

Online joeqsmith

  • Super Contributor
  • ***
  • Posts: 8351
  • Country: us
I don't see any issues with insertion loss, since that should be more straightforward both to measure and to calibrate out.

But, I think that CM attenuation of a given transformer can really only be compared if the systems are the same, because it will depend on the impedance of the instrument ground path relative to the cable ground path, and this is really unlikely to be the same. However, the measurement description sounds more like a straight attenuation measurement, as if you sent a test signal through an inductor and looked at each of its terminals. In that sense, it should be basically valid at lower frequencies, but it's not really CM attenuation in a well defined sense, even if it correlates well. At high frequencies, you would at least want a fixture, same cables, etc.

Also at high frequencies (upper 10s of MHz and up), you would need to be very careful about intrawinding capacitance as you will get capacitive coupling between turns and this will lower the CM impedance. MgZn cores are a problem in this regard as they are not really a very good dielectric even at DC, and they get worse at high frequencies. NiZn cores are usually much better for this, though it can work with MgZn cores if you space the windings from the core. In either case, and make sure not to overlap windings and keep a sizable gap between the end turns.

Cheers,
John

https://www.nonstopsystems.com/radio/frank_radio_coax-sw.htm
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
Software, documentation and test reports for the low cost NanoVNA & V2 Plus 4 may be found here:
https://github.com/joeqsmith
 

Online joeqsmith

  • Super Contributor
  • ***
  • Posts: 8351
  • Country: us
I've ran a fair number of tests with the low cost VNAs and they seem to throw up some decent numbers.  I had changed back to using our local members firmware to solve a glitch I was seeing with the newer flavors of firmware.  This firmware allows measurements to 10kHz.       

Here the $50 NanoVNA is looking at the common mode attenuation of transformer eight.  I then used AppCAD to overlay this data with the data I had collected with my old HP.  Different cables and adapters were used.    Violet is the Nano, Red the HP and Blue showing Brian's data for the Picotest transformer.   

It would be interesting to run the Picotest transformer on my setup but based on Brian's experience and picture showing his setup, I have little doubt I would see a major difference.   
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
Software, documentation and test reports for the low cost NanoVNA & V2 Plus 4 may be found here:
https://github.com/joeqsmith
 

Online joeqsmith

  • Super Contributor
  • ***
  • Posts: 8351
  • Country: us
The Nano doesn't support log sweeps so I fudge it by sweeping short spans of linear sweeps but calculating them based on a log.  So it's a sort of log linear sweep.   AppCAD doesn't appear to like the odd spaced frequencies.   
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
Software, documentation and test reports for the low cost NanoVNA & V2 Plus 4 may be found here:
https://github.com/joeqsmith
 

Online JohnG

  • Frequent Contributor
  • **
  • Posts: 401
  • Country: us

https://www.nonstopsystems.com/radio/frank_radio_coax-sw.htm

Looks like a good link overall. Lots of useful measurement techniques. The definition of CM attenuation is lacking, though. You could have a lossless shield and still get attenuation, so damping is not the reason it works.

I guess the real problem is that the CM current is the one that passes through the instrument ground impedance Zg. The CM attenuation would be how much this current is reduced. So, his measurement will correlate to this, but again, since Zg is instrument-dependent, the CM current and it's attenuation can also be instrument dependent. It's also dependent on the cable setup, since it's the fact that the cable shield has non-zero impedance that is the root cause of the CM signal in the first place.

As a result, I don't think it is valid to compare measurements made on different instruments. This is testable by following the above measurement methods on two different instruments with the same transformer and comparing the result on a single graph. Unfortunately, I only have one instrument, and no transformer (or at least none with good rejection below a few 10s of MHz. I did get the cores I ordered, and travel has opened up, so maybe I will get a chance to test this in the coming months.

Edit: Ok, it looks like you did that. I'll have to look into this further to see if I'm missing something. How's it look as you get into 10s of MHz?

Edit2: If at some point you could provide a drawing or photo of the measurement and cabling setup, that'd be great. I would really like to understand better what is going on and what I'm missing. However, I realize I'm asking for free work, so if you don't have one handy, there's no need to do the extra work. I'm just really curious about this now.

He does show the cross-winding on the toroid in the same section, which is good for reducing the capacitance between input and output.

But, I guess it doesn't matter that much in the end. If it's good enough to make low impedance measurements into the milliohm range, that's what I'm after, and it does look like the basic method is suitable. At some point when my current workload lets up, I hope to pick this up again.

Cheers,
John
« Last Edit: May 22, 2021, 08:46:47 pm by JohnG »
"Those who learn the lessons of history are doomed to know when they are repeating the mistakes of the past." Putt's Law of History
 

Offline coppercone2

  • Super Contributor
  • ***
  • Posts: 5755
  • Country: us
  • $
I got my reamer and lap in, I will try to make a spring winder now. I think I can drill a small hole in an aluminum welding rod of 1/8 thickness to make the shaft
 

Online joeqsmith

  • Super Contributor
  • ***
  • Posts: 8351
  • Country: us

https://www.nonstopsystems.com/radio/frank_radio_coax-sw.htm

Looks like a good link overall. Lots of useful measurement techniques. The definition of CM attenuation is lacking, though. You could have a lossless shield and still get attenuation, so damping is not the reason it works.

Actually if you look at Brian's, the website linked and my own pictures of the setup, if the shield were lossless, there will no no attenuation.  Any device we place between the two ports that is lossless will have no loss...   :-DD

I guess the real problem is that the CM current is the one that passes through the instrument ground impedance Zg. The CM attenuation would be how much this current is reduced. So, his measurement will correlate to this, but again, since Zg is instrument-dependent, the CM current and it's attenuation can also be instrument dependent. It's also dependent on the cable setup, since it's the fact that the cable shield has non-zero impedance that is the root cause of the CM signal in the first place.

As a result, I don't think it is valid to compare measurements made on different instruments. This is testable by following the above measurement methods on two different instruments with the same transformer and comparing the result on a single graph. Unfortunately, I only have one instrument, and no transformer (or at least none with good rejection below a few 10s of MHz. I did get the cores I ordered, and travel has opened up, so maybe I will get a chance to test this in the coming months.

Edit: Ok, it looks like you did that. I'll have to look into this further to see if I'm missing something. How's it look as you get into 10s of MHz?

As we get above 1MHz the cable losses will minimize the ground loop and we can remove the transformer all together.   When I measured that 100uOhm resistor, it became inductive well below a MHz.   In the attached video, I was measuring some popcorn RF capacitors ESR which was in the 10s of mOhms and I was not using a transformer and we were using a two different sub $150 VNAs to do it.   Again, lets not forget that the thread is about making impedance measurements.   

Edit2: If at some point you could provide a drawing or photo of the measurement and cabling setup, that'd be great. I would really like to understand better what is going on and what I'm missing. However, I realize I'm asking for free work, so if you don't have one handy, there's no need to do the extra work. I'm just really curious about this now.

Beyond the photos Brian, the website and I provided?   I would sketch something up but I'm not sure what I could add that would make it any more clear.   

He does show the cross-winding on the toroid in the same section, which is good for reducing the capacitance between input and output.

But, I guess it doesn't matter that much in the end. If it's good enough to make low impedance measurements into the milliohm range, that's what I'm after, and it does look like the basic method is suitable. At some point when my current workload lets up, I hope to pick this up again.

Cheers,
John

Exactly, measuring impedance is the goal, for this thread anyway.   Getting into the 100uOhm range is certainly possible as I have shown using my home made transformer.   We can't get there with the Nano but I wouldn't be at all surprised to see this change.   I'm impressed with how well that V2Plus4 works.   Seeing it measure that ATC capacitor in the 30mOhm range was an eye opener.   

While the two transformers I put together work well,  they are a bit on the expensive side for the hobbyist.  Hopefully you can come up with something that outperforms what I have shown and is cheap.  I had already gone fairly cheap with connectors but thought about buying some of those $8 connectors from China and see how well they perform.  That's where a lot of my cost is sitting.


Starts about 12:00 in.
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
Software, documentation and test reports for the low cost NanoVNA & V2 Plus 4 may be found here:
https://github.com/joeqsmith
 
The following users thanked this post: Grandchuck

Online JohnG

  • Frequent Contributor
  • **
  • Posts: 401
  • Country: us
I think we are miscommunicating on definitions of loss. I have been using loss in the sense of power dissipation, not attenuation. Damping, for instance, is a lossy (dissipative) phenomenon by definition, i.e. energy transformed to heat. A LC filter with ideal components is lossless in this sense.

I guess in the RF sense, the terms attenuation and loss are frequently used to mean the same thing, e.g. return loss, but it's been a while since I worked in the RF world. In the power world, you can have a "lossless" inductor if you make it out of a superconductor. But, it will still have attenuation if you use it in a filter.

In this same way, lossless cables can still have inductance and therefore shield impedance, and impedance can still result in ground loop problems, even if it is lossless in the dissipative sense.

I have looked through the thread. There is a lot of useful information, to be sure. But, I don't see a clear, meaning mathematical, description of what CM attenuation means. But, I figured out the answer to my own question. You are measuring attenuation in a 50 ohm system, whereas I was trying to understand what the CM attenuation is in a real system, for which the CM signal path is all over the map (or Smith chart). So, in your 50 ohm system, you can make measurements that compare data in a reasonable way, at least at low frequency. But, just about any real CM system will not be 50 ohms, nor is it likely to be real-valued and the same between different instruments.

Cheers,
John

"Those who learn the lessons of history are doomed to know when they are repeating the mistakes of the past." Putt's Law of History
 

Online joeqsmith

  • Super Contributor
  • ***
  • Posts: 8351
  • Country: us
From the thread's title, we are using a VNA to make these measurements and yes VNAs (and most RF equipment) will commonly use 50 ohms.   Using a transformer like this to brake the ground look between the two ports is also common practice. 

Does the power world for you mean something to do with the AC power grid where you deal with frequencies in the sub kHz?   In this context,  most of your posts make a lot of sense but I wonder why the interest in this topic?  Something work related? 
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
Software, documentation and test reports for the low cost NanoVNA & V2 Plus 4 may be found here:
https://github.com/joeqsmith
 

Online JohnG

  • Frequent Contributor
  • **
  • Posts: 401
  • Country: us
My career started designing RF amps, but most of it has been in power electronics over various sorts. Various sorts means from 50 Hz to about 100 MHz fundamental frequencies, with much of it in the range of 100 kHz to a few 10s of MHz, from standard PWM to class E and F amps. So, I am somewhat familiar with VNAs of both the low frequency type (like the current Omicron Bode 100) and the more standard RF type, as well as basic RF measurement and design. I've also designed some transmission line transformers, and the CM transformer is a sort of balun. In any case, in the power electronics world, loss means watts dissipated as heat, and attenuation means reduction in level. I also spent a fair amount of time diagnosing EMI problems, and CM EMI is often a big problem in EMI.

It's the series-shunt methods that I have less experience with. In my past job I had access to nice impedance analyzers, and I also used low frequency VNAs like the HP3577 in IV mode for impedance measurements. I had good isolation transformers of the conventional type, and used Pearson transformers for current measurement. The IV mode measurement means that the transformer frequency response can be pretty poor and you still get a good measurement. With this approach, I could get sub-milliohm measurements pretty accurately and repeatably. I also had access to an HP Q-meter. All this I used to measure filters, transformers, and inductors. Even if the fundamental switching frequencies were in the 100s of kHz, ringing and harmonics meant there was a lot of content at much higher frequencies, where inductors might be past a second or third resonance.

I am interested in this topic now because I am trying to characterize low value shunts up to 100 MHz or higher. I have some designs that appear to work ok, but I have nothing to compare them to. My total inductance budget is < 1 nH, so any conventional current sense solutions blow that out of the water. I'm also interested because I am trying to measure losses in PCB layouts over a wider frequency band. Finally, I am also trying to understand high frequency "ground" currents and ground bounce issues where there are very high, very fast current spikes. I don't have the same access to high end equipment that I once did, or least not RF equipment, so I need to figure out some other ways to do things. This is all work-related. The challenge is that I don't have the luxury of 50 ohm anything. Since they are power conversion circuits, a lot of amps are flowing around at low voltage, so the impedances are generally much lower than 50 ohms.

Cheers,
John
"Those who learn the lessons of history are doomed to know when they are repeating the mistakes of the past." Putt's Law of History
 

Offline coppercone2

  • Super Contributor
  • ***
  • Posts: 5755
  • Country: us
  • $
I found my spring bushing in a rotary joint inside of some old equipment, its a thing
 

Online joeqsmith

  • Super Contributor
  • ***
  • Posts: 8351
  • Country: us
My career started designing RF amps, ..

... This is all work-related. The challenge is that I don't have the luxury of 50 ohm anything. Since they are power conversion circuits, a lot of amps are flowing around at low voltage, so the impedances are generally much lower than 50 ohms.

Cheers,
John

I was with you up to that last sentence.  There are many good educational videos on using 50 ohm systems to measure PDNs.  This thread hardly scrapes the surface.  In many videos, they will demonstrate simulation software available today.   You may enjoy watching some of them. 

My old HP3589A isn't good enough to look at that 100uOhm directly.  My goal is to eventually try and use the Nano to measure a circuit boards PDN.  Now that we have a transformer and DC blocks, it's back to software.   In my case, it's just for the fun of it.   

I have one of Pearson's transformers.  The patents were helpful in understanding how they pulled it off.   Years back, I read this article and tried to replicate their results.     
https://interferencetechnology.com/the-hf-current-probe-theory-and-application/


How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
Software, documentation and test reports for the low cost NanoVNA & V2 Plus 4 may be found here:
https://github.com/joeqsmith
 

Online JohnG

  • Frequent Contributor
  • **
  • Posts: 401
  • Country: us
I'm not measuring PDNs in the traditional sense, though there is a fair bit of overlap. I am trying to model small, very fast switching high-current circuits that might be coupled or attached to a PDN intentionally or otherwise. An imperfect analogy would be that PDN analysis tends to look at things macroscopically, and I need to look more microscopically.

Also looking at simulation software, but the expense is significant so I need to make sure it will meet current and anticipated future needs, and I have very little 3D simulation experience. The other problem is that to really get good at such a tool, it helps to have an experienced employee to go with it.

Cheers,
John

 
"Those who learn the lessons of history are doomed to know when they are repeating the mistakes of the past." Putt's Law of History
 

Online joeqsmith

  • Super Contributor
  • ***
  • Posts: 8351
  • Country: us
I am trying to model small, very fast switching high-current circuits that might be coupled or attached to a PDN intentionally or otherwise. An imperfect analogy would be that PDN analysis tends to look at things macroscopically, and I need to look more microscopically.

Sorry but you would need to provide more details for me to follow.  I consider macro as being something large and micro as small.  You wrote how you want to look in the mOhms where I have posted looking in the uOhms.  Oh wait, it was an imperfect analogy.   :-DD 


How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
Software, documentation and test reports for the low cost NanoVNA & V2 Plus 4 may be found here:
https://github.com/joeqsmith
 

Offline coppercone2

  • Super Contributor
  • ***
  • Posts: 5755
  • Country: us
  • $
you can try to measure the same value 10 times and graph the plot in all the measurements to see the spread, it might have to do with the confidence interval
 

Online JohnG

  • Frequent Contributor
  • **
  • Posts: 401
  • Country: us

Sorry but you would need to provide more details for me to follow.  I consider macro as being something large and micro as small.  You wrote how you want to look in the mOhms where I have posted looking in the uOhms.  Oh wait, it was an imperfect analogy.   :-DD

I'll try to make it better. A PDN is more of a system level concern, basically a network with a lot of objects (sources and loads, loosely speaking). The objects could be a capacitor, an IC with bypassing, a switch-mode converter, etc. I'm looking at switch-mode power stages, which might feed a PDN. Such a stage will have caps, controls, active and passive parts, so tends to have complex behavior on its own. So a person looking from a PDN point of view tends to view these as given impedances on the network, but I zoom in on these details and others, so to speak. The other details relate to power dissipation, power processing density, cost, safety and reliability, etc.

Cheers,
John
"Those who learn the lessons of history are doomed to know when they are repeating the mistakes of the past." Putt's Law of History
 

Online joeqsmith

  • Super Contributor
  • ***
  • Posts: 8351
  • Country: us
This clears things up.  If you decided to make a blog about it, post a link or for that matter, maybe even post it here.  I would like to follow along.
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
Software, documentation and test reports for the low cost NanoVNA & V2 Plus 4 may be found here:
https://github.com/joeqsmith
 

Online JohnG

  • Frequent Contributor
  • **
  • Posts: 401
  • Country: us
If my employer is ok with it, I may able to publish something. They are mostly ok with publications, but first I need to get together enough material to make a reasonable publication. That's a ways off. It's one of those background tasks that keeps getting bumped until results are needed yesterday... I keep chipping away at it, though.

Cheers,
John
"Those who learn the lessons of history are doomed to know when they are repeating the mistakes of the past." Putt's Law of History
 

Online joeqsmith

  • Super Contributor
  • ***
  • Posts: 8351
  • Country: us
I watched about half of this video today where Eric Bogatin, currently the Dean of the Teledyne LeCroy Signal Integrity Academy shows us how to connect a scope to a breadboard.   There is some magic voodoo going on here.       


How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
Software, documentation and test reports for the low cost NanoVNA & V2 Plus 4 may be found here:
https://github.com/joeqsmith
 

Offline Kosmic

  • Super Contributor
  • ***
  • Posts: 2089
  • Country: ca
I watched about half of this video today where Eric Bogatin, currently the Dean of the Teledyne LeCroy Signal Integrity Academy shows us how to connect a scope to a breadboard.   There is some magic voodoo going on here.       




I guess he is using a ground spring ? but I haven't seen any.

The signal was probably pre-recorded anyway and he is "lip synching" the manip  :)
 

Offline YetAnotherTechie

  • Regular Contributor
  • *
  • Posts: 207
  • Country: pt
To Joe:
Why not ask VirtualParticles to open it up and see how it's made?
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf