EEVblog 1743 - Mechanical Vibration Detection with your Oscilloscope Probe

[EEVblog]

Dave shows you how to use your oscilloscope probe to detect mechanical vibrational modes on your PCB. And shows off the Crysound Acoustic Imaging Camera!
https://www.kickstarter.com/projects/pocket-acoustic-cam/crysound-pocket-acoustic-imaging-camera/

[temperance]

This is the number one reason to never use MLCC Class II capacitors in frequency compensation circuits around op amps.

[2N3055]

You could have used FFT too, it would be even more sensitive...

[2N3055]

This is the number one reason to never use MLCC Class II capacitors in frequency compensation circuits around op amps.

They can in fact be used as sensors... 

[temperance]

This is the number one reason to never use MLCC Class II capacitors in frequency compensation circuits around op amps.

They can in fact be used as sensors... 

Indeed, and some op amps can also be used as sensors strain gauges. The off set voltage of LM358's from TI can be adjusted by bending the PCB even just a very tiny bit. The same type from On and ST didn't have this problem.

But apart from that, the signal on the scope appears before the probe is touching the board... 1 April.

[2N3055]

But apart from that, the signal on the scope appears before the probe is touching the board... 1 April.

 

[EEVblog]

This is the number one reason to never use MLCC Class II capacitors in frequency compensation circuits around op amps.

Yes, mentioned that in one of the previous videos.

[TUMEMBER]

But apart from that, the signal on the scope appears before the probe is touching the board... 1 April.

 

Don't worry, "here" (in Europe) it's still March 31, 2026. Don't go banging your head against the wall like that, you'll hurt yourself unnecessarily.

[electr_peter]

Crysound acoustic camera in a small and portable form factor looks very interesting based on Dave's video. Pretty sure they will deliver Kickstarter campaign by the looks of it.

[golden_labels]

This is why you never use internet-connected scopes in R&D and military. There is a risk of eavesdropping through scope probes lying all across the laboratory.

If you really have to, use in-line speech attenuators:



They are pretty expensive (the one above is $4200 a piece), but they don’t affect your measurements. Only uncorrelated but (on a longer timescale) coherent speech signal is attenuated. The kind a random chat would generate.

[f4eru]

Video is fishy, but....
Actually, I made MLCCs sing:
1nF 2kV or so, make sure it's a bad dielectric class...
feed in a square 4 kHz 600V p-p.
It audibly sings.

[Ranayna]

Video is fishy, but....
Actually, I made MLCCs sing:
1nF 2kV or so, make sure it's a bad dielectric class...
feed in a square 4 kHz 600V p-p.
It audibly sings.

Coilwhine and capacitor rattling is well documented in PCs, especially high power gaming PCs.
I think everything about the video is real (And that acoustic camera looks incredible, if too expensive as just a gadget.

Only the last thing with the scope touching the cap to pick up its vibration... *That* is fishy

[rteodor]

Why is the camera FFT showing Dave's voice up to 40..50KHz ?

[Kleinstein]

The scope probe is picking up 11 kHz, while the acoustic camera showed 22 kHz. So chances are the scope probe still pics up an electromagnetic field, not acoustic.

The scop probe may have an MLCC inside, but that would be a low value (e.g. 5-10 pf) C0G type and these are not piezo electric.
The effect from hitting the probe is more from plastic isolation. Plasticaly deformed PVC and some others (PTFE ?) can become piezo electric. Another part is triboelectric charges in the cable - directly and as trapped static charges with changes in the capacitance.

A scope probe to detect vibrations would still be a nice project. One could use somerhing like a small piezo element, e.g. from an acoustic delay line or maybe cut up a beeper disc. An old turntable pickup (e.g crystal type) may also work. These are much more sensitive than a MLCC that is made to minimize the piezo effect.

[Kleinstein]

Why is the camera FFT showing Dave's voice up to 40..50KHz ?

That is a good question. There can actually be some contend to higher frequencies in the voice, but it could also be harmonics in the signal chain. It still looks like a pretty strong effect.

[rteodor]

Why is the camera FFT showing Dave's voice up to 40..50KHz ?

That is a good question. There can actually be some contend to higher frequencies in the voice, but it could also be harmonics in the signal chain. It still looks like a pretty strong effect.

In addition to those, there could be some nonlinearity in the FFT scale too aggravating the displayed spectrum.

In ElectroBOOM's video ("Only 20k to Fix a Flat Tire" - where he uses a Fluke acoustic camera) there isn't any visible ultrasonic voice. There is a bit of this effect in The Signal Path review of Fotric camera where it seems to appear only when there are strong voice sounds and its not that spread in frequency. Yet its present all the time in this camera.

[Sorama]

How low in frequency would an MLCC  be able to pick up mechanical vibrations?

I’m still looking for a device than can pick up the noise generated by a water leak in a pipe for domestic use.

I have a device that does that, but it does not work well.
I know from concurrent companies that there is no such (good working) device anymore on the market.

[2N3055]

How low in frequency would an MLCC  be able to pick up mechanical vibrations?

I’m still looking for a device than can pick up the noise generated by a water leak in a pipe for domestic use.

I have a device that does that, but it does not work well.
I know from concurrent companies that there is no such (good working) device anymore on the market.

Did you try piezo pickups for guitar or bass? There are many piezo vibration sensors around too..

[Sorama]

I even don’t know what a guitar pickup is…until now.
Tnx.

[temperance]

I even don’t know what a guitar pickup is…until now.
Tnx.

The "are you fookin ready" computer generated pling plong music generation. 

[Sorama]

I even don’t know what a guitar pickup is…until now.
Tnx.

The "are you fookin ready" computer generated pling plong music generation. 

Not me.
I installed Olivetti computers in 1986 in my father’s company.
I don’t even use social media…

[2N3055]

I even don’t know what a guitar pickup is…until now.
Tnx.

The "are you fookin ready" computer generated pling plong music generation. 

Not me.
I installed Olivetti computers in 1986 in my father’s company.
I don’t even use social media…

Olivetti M19 was first IBM PC compatible I worked on, in 1987...Good times..

[Sorama]

I even don’t know what a guitar pickup is…until now.
Tnx.

The "are you fookin ready" computer generated pling plong music generation. 

Not me.
I installed Olivetti computers in 1986 in my father’s company.
I don’t even use social media…

Olivetti M19 was first IBM PC compatible I worked on, in 1987...Good times..

I started with M24, M28 and M290.
Harddisk was 20MB, DOS 3.0

[temperance]

Real computers where you could just brew your own interfaces with some tri state buffers and latches with a 74HCT138 doing the address decoding.

[2N3055]

Real computers where you could just brew your own interfaces with some tri state buffers and latches with a 74HCT138 doing the address decoding.

Yep.. You could slap together ISA card if you put some effort into it.