EEVblog #983 - A Shocking Oscilloscope Problem ! aka Whack Triggering ...

[BravoV]

R&S new feature Whack Triggering ... 

[BravoV]

Actually its not a big deal if there is no touch screen, but now I guess R&S is considering to modify the user manual that stated under certain measurement condition, user should "gently" touch the screen and nails cut ? 

[tatus1969]

I bet that it will also trigger when you clap your hands close to it!

[FrankBuss]

I bet that it will also trigger when you clap your hands close to it!

It didn't trigger when he tapped on the bench. And I don't think it is a big deal. How often do you use the 20 mV range and then the touchscreen? But the noise performance at these low range setting looks awesome, compared e.g. to the Keysight scope you can see in the video (I have a Keysight, too, it is not amazing in this regard).

[EEVblog]

And I don't think it is a big deal. How often do you use the 20 mV range and then the touchscreen?

What has the touchscreen got to do with the range you use?
It's a touch screen scope, so it's pretty reasonable to expect that touching the screen does not impact your measurements.

But the noise performance at these low range setting looks awesome, compared e.g. to the Keysight scope you can see in the video (I have a Keysight, too, it is not amazing in this regard).

Be careful there, it's not apples-apples. Bandwidth, sample memory, and update rate all play a part in how "noisy" a signal looks.

[RoGeorge]

LOL that's a funny finding!

I guess this is how you say "Dude, stop poking me! " when you are an oscilloscope, while showing the (waveform) finger to your user 

P.S.
My Rigol DS1054Z does it too.

[FrankBuss]

What has the touchscreen got to do with the range you use?
It's a touch screen scope, so it's pretty reasonable to expect that touching the screen does not impact your measurements.

Maybe. What can you do with the touch screen? It might be useful for moving a cursor or the annotation feature, so maybe often it is in stop mode when using it. But right, could be a problem when you want to move the trigger level with a finger

BTW, the finger draw annotation feature looked silly at first to me, but it could be useful if you want to draw some arrows, infos etc. when trying to show something to colleagues (or in a video blog), or as special markers for yourself while measuring something. I bet the next firmware updates of all the other touch screen scopes will have it, too, easy to implement in software.

[EEVblog]

If you want this problem fixed, just talk to marketing. They'll insist upon the world's first "Low Vibration Front End".
The sales people will love because they'll be able to do side-by-side demos tapping on the competitor BNCs and showing how crap they are!
I'm serious.

LowVib^TM 
or the even better NoVib^TM

[TheAmmoniacal]

A very funny and peculiar issue indeed, not something I had considered before. How would a manufacturer prevent this issue in new models? They don't put this in spec sheets of caps!



@BravoV I don't see this video made public yet? I think you should respect that. (?)

[Brumby]

Dave's right.

Simple demo with striking results - that's a winner.

[TheAmmoniacal]

Dave's right.

Simple demo with striking results - that's a winner.

Mmm.. RTB2004, I'd tap that.

[BravoV]

@BravoV I don't see this video made public yet? I think you should respect that. (?)

Dave posted it 1st and its deep buried in R&S thread -> HERE, (watch the time stamp at his post & this thread 1st post).

Believe not everyone are following that thread, hence I created this one as its suitable in this forum section.

[BravoV]

How would a manufacturer prevent this issue in new models?

Maybe redesign the scope's frame, and sort of separate the screen's section mechanically, and with the stiffened the input board section ? 

[FrankBuss]

How would a manufacturer prevent this issue in new models? They don't put this in spec sheets of caps!

Use 1 cent film capacitors instead of 0.1 cent ceramic caps for the front end.

[ataradov]

Use 1 cent film capacitors instead of 0.1 cent ceramic caps for the front end.

Or even automotive capacitors that are lifted off the board on metal stands.

[Tom45]

Curious about older scopes, I tested:

2465 (1 meg input): noise spikes when tapping the channel 1 or 2 input bnc connectors. Otherwise, nothing when tapping anywhere else on the scope.

2465 (50 ohm input):  Nothing at all

7904 with 7A24 (50 ohm input) : no noise spikes at all no matter where I tried. The 7A24 only goes down to 5 mv/div, but the trace in auto sweep was a complete flat line.

7904 with 7A22 (1 meg input) : noise spike when tapping the + differential input at 2 mv/div. Otherwise nothing at all including tapping on the - differential input.

7904 with 7A26 (1 meg input) : modest noise spike when tapping either bnc connector. Otherwise, nothing. The 7A26 only goes to 5 mv/div.

[Fungus]

On some of them you weren't setting the trigger very low (eg. Siglent). I think most of them will be super-sensitive with the right adjustment.



PS: I'd forgotten how fugly the GW-Instek is. It really is a horrible nicotine-yellow color. If the screen and knobs weren't bright and clean then you'd think it had already spent ten years in a 1970s working man's club.

[chris_leyson]

Couldn't wait to get home and try whack triggering on my 7000 series plugins. Tested a 7A26, 7A42 and a 7D20, if I whack the BNC connectors with a 1LB real of Kester solder I can get nearly 2mV pk-pk trigger signal and if I up the anti and use a 500g coffee jar I get a huge 5mV pk-pk, that was with quite a big whack not just a gentle tap, good job I couldn't find my automatic center punch.

Tried a TEK TDS120 at work and that triggers if you whack the case with a srew driver, 100mV pk-pk if you whack the BNC. Also tried my HP54610B about 100mV if you whack the BNC connectors and that was with a coffee jar. Must admit my Analog Discovery was disappointing, only 5mV pk-pk and that's if you drop onto the bench from about half a meter.

[mikeselectricstuff]

In case you're not following the R&S thread, the issue pretty much vanishes as soon as there is any kind of probe connected, so pretty much a non-issue.
 
What a scope does with an unconnected input just doesn't matter, as you'll never use it like that.

[RoGeorge]

My Rigol DS1054Z keeps triggering when I tap it, even if the probe is attached. Still, the tap needs to be a little stronger with the probe attached (10:1 probe), and even more stronger when the probe is switched to 1:1. Probe tip was shorted to ground in both cases.

With a 50 ohms terminator instead of a probe, it doesn't trigger by tapping any more.

[SeanB]

With the gain of the scope I think this will also happen at higher levels depending on the particular capacitor that is most microphonic. Even a foil capacitor is not immune to this, especially the SM variants, as they also have the thin films inside, and the plastics are going to be somewhat piezosensitive.

Wonder how they will react with input terminated in 1M though, as 50R will pretty much damp any noise coupled through.

Note to users, do not use in moving vehicles, or on aircraft. I do not think Vibrachoc makes a mounting that will attenuate that vibration enough.

[Bud]

The 3-letter agencies are in panic mode. Their secret spying weapon, the microphonic oscilllscopes, is uncovered.

Edit: now we know why mass model scopes do not have 50 ohm input.

[rf-loop]

On some of them you weren't setting the trigger very low (eg. Siglent). I think most of them will be super-sensitive with the right adjustment.



PS: I'd forgotten how fugly the GW-Instek is. It really is a horrible nicotine-yellow color. If the screen and knobs weren't bright and clean then you'd think it had already spent ten years in a 1970s working man's club.

And you forget look that in image Siglent setting is 500uV/div true full BW sensitivity. If compared to Rigol Z box where highest true sensitivity is 5mV/div ( 1mV/div and 2mV/div are just only zoomed from 5mV/div). In video Riglol 1kZ was set for 2mV/div (10x, 20mV/div)

(but whole this thing is partially bland. For what kind things we use oscilloscope with open input connectors?  Of course some peoples may use open inputs for hunting ghosts but this can do also with empty matchbox depending how )

But it is also nice. No need sensor, only chopstic what other end touch bearing housing and other touch scope input bnc. Now we can do ball bearing acoustic health analysis. Free Option.

[EEVblog]

Dave posted it 1st and its deep buried in R&S thread -> HERE, (watch the time stamp at his post & this thread 1st post).
Believe not everyone are following that thread, hence I created this one as its suitable in this forum section.

Thanks, but I'd appreciate if people didn't create threads in here for unreleased videos.

[Tek_TDS220]

My icon is a picture of my scope after taping on the BNC connector!!!   Just kidding, but my TDS220 has a 'microphonic' front end with a 1 Mohm input.  Interesting, but it's not an issue for me.  Of course, the TDS220 doesn't have a touch screen.

[tautech]

My icon is a picture of my scope after taping on the BNC connector!!!   Just kidding, but my TDS220 has a 'microphonic' front end with a 1 Mohm input.  Interesting, but it's not an issue for me.  Of course, the TDS220 doesn't have a touch screen.

The TDS210 and 220 had the BNC's mounted directly to the PCB with no additional fixing to the chassis which seems to dampen the microphonic susceptibility it would seem from the different models of scope that Dave checked.
Tek learnt some lesson from these two models as the BNC's were inclined to bust away from the PCB if subjected to abuse. The TDS1k and 2k did not show anywhere near the same level of problem as their BNC's are fixed with nuts to a steel chassis.

[trophosphere]

I wonder if something like this from Murata would help. Granted it is advertised as the source coming from the capacitor itself it would be logical to assume that it may go both ways?

[Rasz]

the most shocking thing here is a weaksauce clickbait game

[EEVblog]

In case you're not following the R&S thread, the issue pretty much vanishes as soon as there is any kind of probe connected, so pretty much a non-issue.

Nope, it's still a potential issue even with a probe plugged in.
Even with a shorted x10  probe I still get 1-2mV with the poker tap on the screen. Not unexpected as the 9Mohm + low cable cap doesn't present much of a load.
Obviously it's going to be a complex interaction with the source impedance and cable used etc (which are now a "load" for the voltage impulse)
Yes it goes away with a shorted x1 probe (i.e. a low impedance source) but it's not right to say it's not a significant issue when you plug a probe in. I still see it. YMMV?

[Gazza2]

Well I gave my rigol ds2072a some good whacks and found it only triggers on the bnc's. Has Dave started the international slap your scope day?, is this the nerds version of planking?

[Fungus]

the issue pretty much vanishes as soon as there is any kind of probe connected, so pretty much a non-issue.
 
What a scope does with an unconnected input just doesn't matter, as you'll never use it like that.

It's almost as if you missed the part of that video with Dave whacking probes on the bench.

[G7PSK]

What happens in a really noisy environment, such as big diesel engine or gas turbine testing or large amplifiers at concerts etc.

[Brumby]

You wear ear muffs.

[Fungus]

Still waiting for the picoscope results.

[G7PSK]

With a pair on the scope as well 

[mikeselectricstuff]

In case you're not following the R&S thread, the issue pretty much vanishes as soon as there is any kind of probe connected, so pretty much a non-issue.

Nope, it's still a potential issue even with a probe plugged in.
Even with a shorted x10  probe I still get 1-2mV with the poker tap on the screen. Not unexpected as the 9Mohm + low cable cap doesn't present much of a load.
Obviously it's going to be a complex interaction with the source impedance and cable used etc (which are now a "load" for the voltage impulse)
Yes it goes away with a shorted x1 probe (i.e. a low impedance source) but it's not right to say it's not a significant issue when you plug a probe in. I still see it. YMMV?

Probably something they should be checking in production as it will clearly have some dependence on mechanical stress etc. Your unit looks like it's maybe more sensitive.

[bibz]

Maybe yours is more robust? Need more data!

[EPTech]

Hi guys,

I got a Rigol DS4024 here. With probes unplugged and sensitivity on 2mV/div and trigger just above the noise and mode set to normal I have to tap the case quite firmly to get a trigger. On the BNC's I get a spike of about 10mV. Once the probe is connected there is no noticeable microphonic effect on the BNC's, as Mike stated, which is good.

The passive probes that came with the Rigol are very microphonic though. I can even pick up my voice if I talk loud enough. When I took off the tip (hook) the effect went almost completely away. It seems my probe is only microphonic when the probe tip is on there. Any ideas on that? Is the contact inside the probe tip causing this maybe? Is friction between the plastic parts causing minute static potentials?

[IAmBack]

I did another experiment with my 1054z.
I've put 50ohm terminators and then poked the scope (i didn't want to turn off input).
And microphone effect vanished on terminated inputs!
I've some explanation of this phenomena, but I'll wait for experimental confirmation from You.

[mikeselectricstuff]

I wonder if it may also depend on the surface it's sitting on - a hard surface would probably conduct shock away from the scope btter than a soft one.

 

[SeanB]

I tried with the Tenma scope I got from Toploser, and it needs a fair whack to get a response, so I guess pretty much all scopes will have this. But then again, an analogue scope would do the same if tapped, because the deflection plates in the tube move inside the tube supports.

You really had to have pretty good tube design, with massive internal support structures, extra bracing along the edges and at the rear, thicker plates and added vibration mountings, so there were no resonant points inside the aircraft vibration envelope to get a CRT to survive in aircraft. They also had to have much thicker glass faceplates and some scary scanning design, so you got a flat faceplate, though there you were slightly less worried about tube depth in the panel, so you could have a long beam throw making the deflection correction easier in the small scan arc, as opposed to consumer which wanted 110 degrees of scan and more to keep the depth down. Drawback was you really ran the phosphor hard to get good brightness and daylight contrast, and the front ran pretty hot in operation.

[luisprata]

DSO-X2004 results
Para os brasileiros que acompanham o Forum.

[metaxis]

Shock mounts may have unacceptable trade-offs.  Case/bench isolation should be doable, but I suspect it's hard to avoid mechanical coupling from the BNC to the frontend while still providing a fixed, stable  EM environment.

Interesting article from TI on "Stress-induced outbursts: Microphonics in ceramic capacitors" shows this in a DUT.

https://e2e.ti.com/blogs_/b/precisionhub/archive/2014/12/19/stress-induced-outbursts-microphonics-in-ceramic-capacitors-part-1

https://e2e.ti.com/blogs_/b/precisionhub/archive/2014/12/23/stress-induced-outbursts-microphonics-in-ceramic-capacitors-part-2

[EEVblog]

I wonder if it may also depend on the surface it's sitting on - a hard surface would probably conduct shock away from the scope btter than a soft one.

It's a complex resonance mode system thing. Think of the bench as the acoustic equivalent of an RF stub. (they are actually directly equivalent systems, just the mediums and wavelengths differ)

[EEVblog]

And microphone effect vanished on terminated inputs!
I've some explanation of this phenomena, but I'll wait for experimental confirmation from You.

Of course it vanishes. 50ohms is stupidly low impedance compared to a microphonic MLCC cap source impedance.
But of course it depends on where in the front end system chain the offending "singing" cap is located.
If it's after the FET input buffer then you can forget about the input termination doing anything at all.
But by design is almost always likely to be on the input side of the buffer, because the output buffer is going to be low impedance system at that point, so any caps there won't be a problem.

[JPortici]

Still waiting for the picoscope results.

i see if i have time to switch it on later today!
by the way, that tektronix TPS of mine was a real mess: at 20 mV/Div (10x, BW Limit) tapping on scope produced spikes greater than 100 mV, they go outside the screen. but it has never been an issue while working on cars as far as i know it (we don't put it over the engine, but rather on the plastics around the compartment)

edit: it was harder than other scopes. i pretty much had to keep it in one hand while i was beating it

[timgiles]

Interesting papers referenced above. Nice to see some actual real world comparisons?.

I wonder if any one has an idea of the cost increase on a typical frontend if all caps were replaced with tantalums / film caps?

[mikeselectricstuff]

Interesting papers referenced above. Nice to see some actual real world comparisons?.

I wonder if any one has an idea of the cost increase on a typical frontend if all caps were replaced with tantalums / film caps?

It's only going to be something right at the input of the front end, as shorting the input makes it disappear, so will be very small capacitances. I'm not sure there is any alternative to ceramics at these low capacitances. Digikey shows nothing else at 10pf.
If you think how small the required charge is to produce a 1mV spike on a 1megohm input with 10pf capacitance, I doubt it is even possible to eliminate mechanical effects as most components will have some sensitivity to mechanical stresses, and you need to consider a wide range of mechanical frequencies.
The only solution would be careful mechanical isolation, and that would be hard to do without increasing input capacitance. Even something crude like potting the input stage in a suitable damping resin is going to increase stray capacitances. 
 

[madires]

Hameg 1508-2 (CRT): about 2mV pp for a gentle tap on the BNC and about 8mV pp for a proper tap. A tap on the case has a much smaller impact (<0.1mV).

[Stephan_T]

Plugging in a BNC connector can have a huge impact on this problem as mike pointed out. I tested this on my Rigol 1054Z and without even shorting the probe, the impact of tapping on the case and the connector is much smaller compared to a naked BNC socket. Even a BNC T-adapter with nothing else connected dampens the vibrations substantially. So it would be interesting to see the comparison of the different scopes under real world conditions, with probes (open circuit) connected to the inputs.

On my Rigol the Channel 4 seems to be the least effected. Channel 3 is the most microfonic one.

Image 1 shows a tap on the top of the case with
 a T-adapter on channel 1,
 x1 open probes on channel 2 and 3
 and the raw (nothing connected) channel 4.

Image 2 is a similar strike with nothing attached to any connector.

[RGB255_0_0]

Dave, you've been called out by Keysight_Daniel: https://youtu.be/OgDuL-or12c?t=440

[Fungus]

Who wants to see Dave whacking his new $300k dumpster find?

[FrankBuss]

Dave, you've been called out by Keysight_Daniel: https://youtu.be/OgDuL-or12c?t=440

Lol, I'm pretty sure Dave knows how to use single mode and the auto/normal trigger modes. Sometimes single is just better, if you want to catch the first trigger and not mucking around with holdoff, or accidentally catch another trigger, but you wanted to analyze the first triggered signal.

And the Keysight guy shows the piezoelectric effect of the probes, which is well known, while Dave demonstrated it inside the scope, which might be not so well known and varies greatly between scopes.

[mikerj]

I discovered my Owon SDS7102 was horribly microphonic a few years back when I bought it.  This is the result if I flick the Channel 1 BNC socket with a finger nail, about 700mv pk-pk!

[flodins]

I recently got the R&S RTO2024 2GHz 10GS/s 1Mwfms/s 16bit ADC and it seems to be the best. BNCs and frontend are built like a tank. RTM-ZP10 probe is made mainly from a rubber. Only the very tip is made from a plastic and it is susceptible to whack test.

[Damianos]

I wonder what will be the result if someone performs the auto-calibration while listening loud music! 
The manufacturers say "disconnect everything from the inputs". So no damping things will be present there.


Edit: correctness of my stupid English!

[pascal_sweden]

R&S should have used capacitors from Murata for reduced microphonics:

https://books.google.no/books?id=y0kGRzbh-owC&pg=PA43&lpg=PA43&dq=microphonics+murata&source=bl&ots=-R_bm7FLG2&sig=zc2FjzQ2JzfsqAG_ZueYseqFH6s&hl=no&sa=X&ved=0ahUKEwiutsCil4TTAhWqK5oKHUq7AaIQ6AEIITAB#v=onepage&q=microphonics%20murata&f=false

[KedasProbe]

I tried it with a 50 ohm termination on it and then it's too low to detect it on that channel.
So I assume the problem is located before the amplifier. (if it would be after it my to measure circuit output load wouldn't have any influence on it)
This also means it's less likely to happen during measurements since you are not measuring with an open input.

[jonovid]

try tapping your partner? ...jokes aside. 

But seriously-
expensive top of the line oscilloscopes should not have this microphonics problem IMO. 
say your useing the oscilloscope in a industrial environment,  mechanical vibrations from
running industrial plant and equipment can get on the test bench. also what if the test bench is a moving vehicle?
as example, commercial fishing boat at sea. another example aircraft have mechanical vibrations from engines into the fuselage.

[Petter]

I was expecting someone to have replaced input caps on his/hers scope already ...

[mikeselectricstuff]

I was expecting someone to have replaced input caps on his/hers scope already ...

Bit busy at the moment..

[David Hess]

The only way I can do this on my old oscilloscopes is to tap the BNCs directly but what is going on with them has nothing to do with ceramic capacitors; the BNCs in this case are mechanically isolated from the printed circuit boards.

The BNC coaxial insulator between the body and inner conductor is piezoelectric and/or triboelectric and I verified this by attaching a short RG-316 (1) coaxial cable.  The BNC on the end of the cable has roughly the same sensitivity as the oscilloscope BNCs and the cable itself is even more sensitive.  If I connect the inputs together with the cable, then both channels show exactly the same thing no matter where on the BNCs or cable I tap.  The high impedance vertical inputs are operating as charge amplifiers and when the input are shorted together, they see exactly the same signal produced by charge in the BNCs and cable.

If I tap the bodies of the oscilloscopes, I have to get close to the BNCs to have any effect unlike most of the examples in Dave's video.

They make specially rated connectors including BNCs and cable for applications where this is a problem.

I agree with Dave; it is insane that tapping the touch screen on the RTB2004 as lightly as he did has the effect he showed.  Even tapping the body should not do anything unless it is coupling into the BNCs themselves.

(1) RG-174 sized but with a Teflon dielectric and silver plated shield and center conductor.  It is just what I had in front of me.

[Fungus]

But seriously-
expensive top of the line oscilloscopes should not have this microphonics problem IMO. 
say your useing the oscilloscope in a industrial environment,  mechanical vibrations from
running industrial plant and equipment can get on the test bench. also what if the test bench is a moving vehicle?
as example, commercial fishing boat at sea. another example aircraft have mechanical vibrations from engines into the fuselage.

Chill.... it's only down in the millivolt range, unlikely to affect most things.

[mtdoc]

But seriously-
expensive top of the line oscilloscopes should not have this microphonics problem IMO. 
say your useing the oscilloscope in a industrial environment,  mechanical vibrations from
running industrial plant and equipment can get on the test bench. also what if the test bench is a moving vehicle?
as example, commercial fishing boat at sea. another example aircraft have mechanical vibrations from engines into the fuselage.

Any environment where vibration levels are high enough to trigger this issue when a probe is attached is going to cause bigger issues for your measurements IMO.

If you were in such an extreme environment, a vibration isolation table would be needed.  These are pretty much standard fare for any sensitive electrophysiology measurements where vibration from someone just walking by your measurement set-up can cause problems.

I think this issue is being overblown.

[joeqsmith]

In case you're not following the R&S thread, the issue pretty much vanishes as soon as there is any kind of probe connected, so pretty much a non-issue.
 
What a scope does with an unconnected input just doesn't matter, as you'll never use it like that.

Yep.  Repeat the test with the probes attached, then tap the BNC end of the probe..  Even that is not something I do.  I don't even tap the chassis.  Tapping the touchscreen on my scope is no problem but I run it with the mouse.   Now fire up my ignition tester in the same room, the LCD will start to act up and the mouse will hang and need to be unplugged to recover.   

[EEVblog]

Dave, you've been called out by Keysight_Daniel: https://youtu.be/OgDuL-or12c?t=440

LOL!
The impulse he's getting is from the MLCC cap in the x10 probe, not inside the scope.
Not that his rant had anything to do with the microphonic problem anyway.

[EEVblog]

In case you're not following the R&S thread, the issue pretty much vanishes as soon as there is any kind of probe connected, so pretty much a non-issue.
 What a scope does with an unconnected input just doesn't matter, as you'll never use it like that.

Yep.  Repeat the test with the probes attached, then tap the BNC end of the probe..  Even that is not something I do.  I don't even tap the chassis.  Tapping the touchscreen on my scope is no problem but I run it with the mouse.   Now fire up my ignition tester in the same room, the LCD will start to act up and the mouse will hang and need to be unplugged to recover.   

I'll repeat this again. I have tried using a shorted x10 scope probe and I can still get the problem.
Yes it's diminished in amplitude but it's still possible.
Do I have to make a video showing this?

Also, be fully aware that x10 probes contain microphonic MLCC's too, sometimes in the probe tip, other times in the base of the cable in the BNC box.
I have done a video on this years ago and part of it was included my Shocking video.
I showed this in my videos, and it's 10 times worse than tapping the BNC.

[KedasProbe]

Maybe you can make a video 'fixing' an input channel of one of your many scopes and then with the '300k' scope you can check if the BW is still ok. 

[pascal_sweden]

Dave mentioned Murata in his follow-up video about this issue. I wonder if that was based on my below comment

R&S should have used capacitors from Murata for reduced microphonics:

https://books.google.no/books?id=y0kGRzbh-owC&pg=PA43&lpg=PA43&dq=microphonics+murata&source=bl&ots=-R_bm7FLG2&sig=zc2FjzQ2JzfsqAG_ZueYseqFH6s&hl=no&sa=X&ved=0ahUKEwiutsCil4TTAhWqK5oKHUq7AaIQ6AEIITAB#v=onepage&q=microphonics%20murata&f=false

[Petter]

I am a little curious as to which caps are causing the problem in the first place. It seems strange to me that you would need a lot of capacitance in the signal circuit proper, hence C0G or whatever capacitors might be usable and they should be very stable wrt shock.

If the caps are in the decoupling of any power rails that could explain large values and the desire to use capacitors with many layers. The obvious solution in that case would be to use tantals + smaller ceramics in tandem. Now this probably introduces a cost problem which the manufacturers don't care to pay for.

I challenge Dave to fix this problem and do a cost analysis of the fix. That would enable the industry to move forward on this issue and help out with edge cases and touch screen usage .

[joeqsmith]

In case you're not following the R&S thread, the issue pretty much vanishes as soon as there is any kind of probe connected, so pretty much a non-issue.
 What a scope does with an unconnected input just doesn't matter, as you'll never use it like that.

Yep.  Repeat the test with the probes attached, then tap the BNC end of the probe..  Even that is not something I do.  I don't even tap the chassis.  Tapping the touchscreen on my scope is no problem but I run it with the mouse.   Now fire up my ignition tester in the same room, the LCD will start to act up and the mouse will hang and need to be unplugged to recover.   

I'll repeat this again. I have tried using a shorted x10 scope probe and I can still get the problem.
Yes it's diminished in amplitude but it's still possible.
Do I have to make a video showing this?

Also, be fully aware that x10 probes contain microphonic MLCC's too, sometimes in the probe tip, other times in the base of the cable in the BNC box.
I have done a video on this years ago and part of it was included my Shocking video.
I showed this in my videos, and it's 10 times worse than tapping the BNC.

No need to make a new video on my account.  Pick what you consider is a sensitive scope and just run the various probes across it, tapping just the body.  Skip the tip.   Take what you consider is the least sensitive 10X probe and try it on each of the remaining scopes.  Do you see different results?   This could be a huge matrix..  You need a controlled tapper as well.  Sorry, I tend to hyper focus if you have not yet sorted that out....

[bktemp]

I am a little curious as to which caps are causing the problem in the first place. It seems strange to me that you would need a lot of capacitance in the signal circuit proper, hence C0G or whatever capacitors might be usable and they should be very stable wrt shock.

If the caps are in the decoupling of any power rails that could explain large values and the desire to use capacitors with many layers. The obvious solution in that case would be to use tantals + smaller ceramics in tandem. Now this probably introduces a cost problem which the manufacturers don't care to pay for.

I challenge Dave to fix this problem and do a cost analysis of the fix. That would enable the industry to move forward on this issue and help out with edge cases and touch screen usage .

Maybe the capacitor for AC coupling the signal (probably the big one next to the optocoupler).
There seem to be quite a lot of different capacitors in the signal path. The grey ones are typically C0G while the brown ones often have a higher capacitance.



It is probably difficult to solve the problem without reverse engineering at least the complete input section (probably coarse input range selection switch) of the frontend.

Image from Mike's teardown video:

[Petter]

Probably right about that.
So it should be quite easy to desolder that part and measure it - then figure out if if falls into the C0G or whatever range, perhaps stacked 3 high or whatever.

If it is easy to get to this while operating the scope, it should be a decent test to tap it directly. I can't remember how hard it was to get to this point in the teardown.

I would think that the smaller parts are safe. Since this scope operates at only 300MHz, serious reverse engineering is unlikely to be very important. Smack a replacement in, test scope for linearity and shock sensitivity, then done if it works.

[Keysight DanielBogdanoff]

Dave, you've been called out by Keysight_Daniel: https://youtu.be/OgDuL-or12c?t=440

LOL!
The impulse he's getting is from the MLCC cap in the x10 probe, not inside the scope.
Not that his rant had anything to do with the microphonic problem anyway.

Haha, the point was definitely about triggering and not about the piezoelectric thing - I saw a teachable moment and couldn't pass it up

[mikeselectricstuff]

I have a couple of suspicions about other possible factors - quite possible there are multiple contributung factors.
The plastic in the BNC connector (triboelectric)- banging a bnc plug on the end of a cable does cause some effect.
Another possibility- if there is a sensitive node that has DC bias on it, then variations in stray capacitance to that node will produce a signal. I'm specifically thinking about the shielding cans - even a small vibration of the can could have a significant effect. I wonder if this might be a reason for the use of copper cans, though I'd think there would be cheaper and better ways to damp vibrations, like sticking heavy tape on.

[egonotto]

Hallo,

@flodins:
flodins wrote:
"I recently got the R&S RTO2024 2GHz 10GS/s 1Mwfms/s 16bit ADC".

Are you sure that has a 16bit ADC?


I tab with a blue ball pen on the BNC of a picoscope 5243A and a picoscope 4262

It is no problem for normal work.

Best regards
egonotto

 

[David Hess]

I played with some other oscilloscopes (7A18, 7A26, 2445B, 2247A, and 2232) and got the same results at about the same levels of roughly 4 to 10 millivolts peak-to-peak.  The impulse in all cases appears to be coming from the BNC itself and I ran other tests using different adapters and coaxial patch cords which seemed to show the same thing.

I tested the 2445B because it thought maybe a high impedance input built as part of a hybrid would perform better or at least different but the results were the same.

Another source that I have not seen mentioned is the printed circuit board or substrate that the high impedance circuits and buffer are built on.  Tektronix had enough problems with hook on FR4 laminates that they used other substrates for their early printed circuit high impedance circuits.  The 7A18 (polysulfone I think) and 7A26 (something white) that I tested use special substrates but normal printed circuit construction.

[KedasProbe]

The good thing is there is a very good measuring device attracted to it to locate it    (your scope)
Just a few ideas:
- based on the time difference on each channel you can find the vibration travel speed (or multiple)
(in an ideal case you could do like some opposite triangulation, like you know the source but want to find the 3 sensors)
- Pressing something close to the vibration sensor will reduce the signal, this may help you locate it (can be hard if multiple sensors are present per channel) the problem here will be a constant vibration source, attaching some small mechanical oscillator (speaker...) to your coax can make this constant. Or getting closer with a source to the sensor will increase the amplitude,

[Stephan_T]

Hi Dave,

at the end of #938 part 2 (@8:03min) you explicitly talk about high impedance loads/sources, but you only showed shorted probes. In my previous post I already presented some  high impedance results for my Rigol DS1054Z.
Just the mechanical presence of some mass on the BNC connector seam to have a significant damping effect alone.

For high impedance circuits capacitive coupling (of 50Hz fields) and EMF from moving charges has a much larger impact on real measurements.

For an other test I mounted 3 different probes side by side on the back of a chair as far away from the desk as possible.
channel 1 = open BNC (for comparison of microphonic effect)
channel 2 = 1x probe
channel 3 = 10x probe
channel 4 = 100x probe

Image 3 shows the effect of a bang on the top of the case compared to the pick up of 50Hz just by the tiny pins of the probes (nothing attached to the probe) The nearest mains cable was at least 1m away from the probes. You can see how the open BNC (yellow channel 1) is showing the noise of the bang, but only channel 3 (magenta) is slightly effected. In my previous tests I already found, that channel 3 is the weakest (most microphonic) one.

But compare this now to the EMF impact of an electrostatic charge on a PVC pipe waved 50cm away from all the three probes shown in Image-4. And remember: only the 5mm long tiny pins of the probes are acting here as "antennas" to pick this up.

Image-5 demonstrates how much larger the EMF and 50Hz signals become, when the standard spring hooks are attached to the probes.


BTW. with a 1m cable on a DMM I can pick up a "Harry Potter" like waving of the (electro-statically charged) magic PVC wand even from 3m distance.   

[EEVblog]

Hi Dave,
at the end of #938 part 2 (@8:03min) you explicitly talk about high impedance loads/sources, but you only showed shorted probes.

The shorted x10 probe was representative of a high impedance source. Effectively the 9M resistor in the probe.

[joeqsmith]

Thanks for running this. 

At 1:50 "which it does by the way", does this mean you tried the other scopes used in the first video and the effect of tapping the probes base vs directly on the BNC eliminates or greatly reduces the effect?   If so, did you see much of a difference between scope probe combos?

[joeqsmith]

Just as a reference, my old LeCroy with touch screen.  With and without the probe. 
https://www.youtube.com/watch?v=q3Itb5TCjLE&feature=youtu.be

[BravoV]

Just as a reference, my old LeCroy with touch screen.  With and without the probe. 
https://www.youtube.com/watch?v=q3Itb5TCjLE&feature=youtu.be

Looks like LeCroy did their homework pretty well, I can see while without the probe connected, you tapped the screen quite hard and its not affected. 

[ataradov]

Looks like LeCroy did their homework pretty well, I can see while without the probe connected, you tapped the screen quite hard and its not affected. 

That LeCroy is heavy. Transferring energy from the screen to the PCB is much harder in that case. Attach a chunk of led to R&S and you will get similar result.

[mtdoc]

I just watched the "part 2" video.  Dave should be arrested for oscilloscope abuse. Every time he stabbed the screen with his plastic poker I cringed. Seriously, who treats an oscilloscope like that? It's a touch screen not a "stab with a plastic poker" screen.

Maybe it's just me but I was taught that when you are measuring small signals you don't touch anything during the measurement. Not only is this "not a big issue in everyday use" as Dave says but IHMO it's not an issue at all in any proper use of an oscilloscope.  Really!

[joeqsmith]

Just as a reference, my old LeCroy with touch screen.  With and without the probe. 
https://www.youtube.com/watch?v=q3Itb5TCjLE&feature=youtu.be

Looks like LeCroy did their homework pretty well, I can see while without the probe connected, you tapped the screen quite hard and its not affected. 

After a fair amount of TLC, I've been fairly happy with it.    I do play around with some projects that emit enough RF to cause the LCD to flicker but other than that and it's poor case, it's solid.  The probe I show was a LeCroy PP002A.

My scope includes a plastic poker stick to stab it with.  I've never used it and normally keep the touch screen turned off.  I like the mouse and keyboard.   

[Bud]

The impulse in all cases appears to be coming from the BNC itself and I ran other tests using different adapters and coaxial patch cords which seemed to show the same thing.

Yes I tried tapping a open BNC connector on the other end of the patch cord, same thing. An even tapping an unterminated coax cable with no connector on the far end does the same. I fact it seems tapping the coax has a more severe effect then tapping the connector. So yes, no escape 

[BravoV]

Looks like LeCroy did their homework pretty well, I can see while without the probe connected, you tapped the screen quite hard and its not affected. 

That LeCroy is heavy. Transferring energy from the screen to the PCB is much harder in that case. Attach a chunk of led to R&S and you will get similar result.

Exactly my point, and that is not a rocket science isn't it ? Either using a piece of heavy lead .. or other "more advanced & creative" mechanical solution which I believe R&S engineers capable of doing it. 

We are not talking a sub $500 scope here, isn't that normal to have "a bit" of higher expectation ?

[Fungus]

Looks like LeCroy did their homework pretty well,

Either that or they got lucky. Or their scopes simply weigh more so you need to hit them a lot harder.

"Never attribute to cleverness that which can be adequately explained by dumb luck" - Fungus.

[gnif]

For some reason hitting people triggers them too 

[Fungus]

We are not talking a sub $500 scope here, isn't that normal to have "a bit" of higher expectation ?

Maybe it's just that nobody ever saw it as a real problem in the 60+ years they've been making oscilloscopes.

Oscilloscope probes are usually held in soft squishy supports or rigidly attached to the DUT. I've never seen a qualified engineer try to take a reading by bashing the circuit with the probes.

[ataradov]

I've never seen a qualified engineer try to take a reading by bashing the circuit with the probes.

Not a day goes by without me punching a scope while doing measurements on the mV scale

I agree, the whole thing is a cool party trick, but no further action is required on the side of manufacturers.

[Fungus]

Not a day goes by without me punching a scope while doing measurements on the mV scale

Maybe you could try cleaning the trigger adjustment potentiometer.

[RoGeorge]

For some reason hitting people triggers them too 

Brilliant!
 

You, Sir, win the Internet for today!

[KedasProbe]

I've never seen a qualified engineer try to take a reading by bashing the circuit with the probes.

Not a day goes by without me punching a scope while doing measurements on the mV scale

I agree, the whole thing is a cool party trick, but no further action is required on the side of manufacturers.

It's not that important but would be nice.
Could be annoying if your environment generates much vibration or if the vibration is the source your DUT is measuring.
The next generation scopes will have "vibration proof" in the feature list

[EEVblog]

Maybe it's just me but I was taught that when you are measuring small signals you don't touch anything during the measurement. Not only is this "not a big issue in everyday use" as Dave says but IHMO it's not an issue at all in any proper use of an oscilloscope.  Really!

If you know about the effect, and that is the point of the videos. I thought that was obvious, but it seems not, as quite a few have complained the videos were pointless.
There would be a hell of a lot of people who would have no idea it was even possible.
And BTW, it's not uncommon to accidentally bump your scope probe etc (which are very susceptible), and I have seen accidental impulses in real use. Luckily I knew what caused it, others might think it's a real signal, or an accidental trigger could send you up the garden path etc.

[bktemp]

Maybe it's just me but I was taught that when you are measuring small signals you don't touch anything during the measurement. Not only is this "not a big issue in everyday use" as Dave says but IHMO it's not an issue at all in any proper use of an oscilloscope.  Really!

If you know about the effect, and that is the point of the videos. I thought that was obvious, but it seems not, as quite a few have complained the videos were pointless.
There would be a hell of a lot of people who would have no idea it was even possible.

Maybe you should do a video on how to deal with high impedance sources / low level signals & currents.
There are many possible topics like how to deal with noise from mains (both 50/60Hz + harmonics and all the other high frequency noise from SMPSs) or other error sources like triboelectric effect or errors caused by thermoelectric voltages.
You have mentioned some of them in other videos but I can't remember a full video on those topics.

[Fungus]

Could be annoying if your environment generates much vibration

Only if nobody ever invents a thing called "foam rubber" and decides to sell it all over the place at really low prices.

[KedasProbe]

Could be annoying if your environment generates much vibration

Only if nobody ever invents a thing called "foam rubber" and decides to sell it all over the place at really low prices.

There are almost always ways around it but it would be nice if the way around was build in the scope. (if it cost very little)
I hope someone would give it a try to prove that with a spare scope.

[mtdoc]

There are almost always ways around it but it would be nice if the way around was build in the scope. (if it cost very little)

The fact that no one has is testament to the fact that this is a complete non-issue in real world use.

[jonovid]

There are almost always ways around it but it would be nice if the way around was build in the scope. (if it cost very little)

The fact that no one has is testament to the fact that this is a complete non-issue in real world use.

microphonics noise tolerance specifications should be listed by the oscilloscope manufacturer?  IMO
so the informed engineer can make decisions as to which oscilloscope to purchase.
if high microphonics noise tolerances are required.   

[mikeselectricstuff]

More from Daniel :
https://community.keysight.com/community/keysight-blogs/oscilloscopes/blog/2017/04/05/the-piezoelectric-effect-and-oscilloscopes

[FrankBuss]

More from Daniel :
https://community.keysight.com/community/keysight-blogs/oscilloscopes/blog/2017/04/05/the-piezoelectric-effect-and-oscilloscopes

Good advice in the article for those who live in Australia: "If you are extra concerned about this or work on the back of a kangaroo, try using an equipment cart or table that has built-in suspension."

[gnif]

More from Daniel :
https://community.keysight.com/community/keysight-blogs/oscilloscopes/blog/2017/04/05/the-piezoelectric-effect-and-oscilloscopes

I wonder if they would send Dave a DSO for drop testing in the true canyoning multimeter style

[Nobody2]

Wow, I knew that capacitors can be susceptible by mechanical stresses, but I would have never ever guessed that measurements could be influenced just by lightly tapping the equipment.

[David Hess]

The impulse in all cases appears to be coming from the BNC itself and I ran other tests using different adapters and coaxial patch cords which seemed to show the same thing.

Yes I tried tapping a open BNC connector on the other end of the patch cord, same thing. An even tapping an unterminated coax cable with no connector on the far end does the same. I fact it seems tapping the coax has a more severe effect then tapping the connector. So yes, no escape 

I had considerable difficulty testing BNCs without the effect of the cables which was almost always greater.

Maybe it's just me but I was taught that when you are measuring small signals you don't touch anything during the measurement. Not only is this "not a big issue in everyday use" as Dave says but IHMO it's not an issue at all in any proper use of an oscilloscope.  Really!

If you know about the effect, and that is the point of the videos. I thought that was obvious, but it seems not, as quite a few have complained the videos were pointless.
There would be a hell of a lot of people who would have no idea it was even possible.
And BTW, it's not uncommon to accidentally bump your scope probe etc (which are very susceptible), and I have seen accidental impulses in real use. Luckily I knew what caused it, others might think it's a real signal, or an accidental trigger could send you up the garden path etc.

It is a real problem in some applications.  I have occasionally had it when making single shot acquisitions where I have to set everything up, arm the oscilloscope, and then trigger the circuit or device under test.  Usually I end up with a few false triggers while I arrange everything or I give up and instead change the test setup to use a trigger source with low sensitivity.

I never considered it a mystery; connectors, cables, and probes suffer from piezoelectric and triboelectric effects.  What I am shocked about is the other examples Dave showed where areas other than the connectors, cables, and probes were sensitive and sometimes much more so; that is just poor and sloppy design.  The touch screen example is particularly egregious.

[mtdoc]

I have occasionally had it when making single shot acquisitions where I have to set everything up, arm the oscilloscope, and then trigger the circuit or device under test.  Usually I end up with a few false triggers while I arrange everything or I give up and instead change the test setup to use a trigger source with low sensitivity.

I never considered it a mystery; connectors, cables, and probes suffer from piezoelectric and triboelectric effects.  What I am shocked about is the other examples Dave showed where areas other than the connectors, cables, and probes were sensitive and sometimes much more so; that is just poor and sloppy design.  The touch screen example is particularly egregious.

I suspect we've all seen it when setting up measurements, moving connectors, probes, etc, even if we didn't know the cause. My point is that it does not or at least should not impact any measurements, unless someone is being a complete boob and bumping their equipment during measurements. Yes,it's good to know about this issue - just as another reminder of why good measurement practices are important when looking at small or sensitive signals.  But again, I think if this had much of a real world impact it woold be common knowledge and scope makers would be addressing  it and marketing this.

As far as the touch screen - i have yet to see any instance where it was triggered with a touch - only instances where it was tapped hard enough to make a sound and when a probe was connected, only when it was stabbed hard with a plastic stick.

[joeqsmith]

Looks like LeCroy did their homework pretty well, I can see while without the probe connected, you tapped the screen quite hard and its not affected. 

That LeCroy is heavy. Transferring energy from the screen to the PCB is much harder in that case. Attach a chunk of led to R&S and you will get similar result.

Steel frame, aluminum case, 68000 VME chassis, this one is heavy.  Pictures showing the interconnect that I mention in the video.

https://www.youtube.com/watch?v=xQ5gyEaCS3U&feature=youtu.be

[KedasProbe]

Required label when you are doing measurements: 

[bitwelder]

Would covering the capacitors in the front-end stage with a blob of silicon glue, celastic or other similar material have any effect in reducing the sensibility to external vibrations?

[joeqsmith]

Only seemed fitting to show something made to operate in a bit more harsh environment.  I'm sure both of these scopes saw much worse over their life in a garage.  My plan is to use them for this same purpose.

[EEVblog]

More from Daniel :
https://community.keysight.com/community/keysight-blogs/oscilloscopes/blog/2017/04/05/the-piezoelectric-effect-and-oscilloscopes

Daniel may not have seen it cause a problem in practice but I have, as have others I know.

[watersb]

Of course some peoples may use open inputs for hunting ghosts but this can do also with empty matchbox depending how ...

Wait, what? An empty matchbox works?

Returning this Owon scope...

I was doing it wrong! Thanks for the tip!