Author Topic: EEVblog #983 - A Shocking Oscilloscope Problem ! aka Whack Triggering ...  (Read 20476 times)

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Online BravoV

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R&S new feature Whack Triggering ...  :-DD

« Last Edit: March 29, 2017, 12:44:13 pm by BravoV »
 

Online BravoV

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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 ?  :-//

Offline tatus1969

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

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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).
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Online EEVblog

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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.

Quote
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.
 

Offline RoGeorge

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LOL that's a funny finding!

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

P.S.
My Rigol DS1054Z does it too.

Offline FrankBuss

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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.
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Online EEVblog

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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.

LowVibTM  ;D
or the even better NoVibTM
 

Offline TheAmmoniacal

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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. (?)
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Offline Brumby

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Dave's right.

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

Offline TheAmmoniacal

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Dave's right.

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

Mmm.. RTB2004, I'd tap that.
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Online BravoV

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@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.

Online BravoV

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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 ?  :-//

Offline FrankBuss

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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.
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Offline ataradov

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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.
Alex
 

Offline Tom45

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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.
 

Online Fungus

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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.

 
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Offline chris_leyson

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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.
« Last Edit: March 29, 2017, 07:10:56 pm by chris_leyson »
 

Offline mikeselectricstuff

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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.
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Offline RoGeorge

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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.

Offline SeanB

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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.
 

Online Bud

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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.
« Last Edit: March 29, 2017, 08:00:51 pm by Bud »
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Offline rf-loop

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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.
« Last Edit: March 29, 2017, 09:07:39 pm by rf-loop »
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Online EEVblog

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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.
 

Offline Tek_TDS220

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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.
 


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