EEVblog #162 - Ceramic Capacitor Piezoelectric Effect on an Oscilloscope

Dave shows how the piezoelectric effect of ceramic capacitors applies to oscilloscope probes, with SHOCKING results.

[DarkEnginseer]

Althoug not beeing an electronic engineer (I'm in mechanical engineering.) I watch your blog with interest (~ for a year), to extend my basic knowledge about electrics/electronics.
Also your industry stories and tips, especially "job interviews" helped me a lot.
Have you ever thought of teaching students at university?
We had at least one Professor who has worked several years in the industry and his very interesting lectures were by far the most important ones, speaking from todays perspective.

[EEVblog]

@HamRadio2008 Thanks. Nice work on the iPad!

[gordonlawrence]

The variable cap will always make a difference and it's a transmission line issue not always a piezo effect. Piezo effect generates a voltage from a force. A capacitor needs some charge differential on it for this to have any effect.

[TeraVoltLabs]

I tried this with my scope, and got the same exact waveform and result. Very good eye to catch that dave!

[EEVblog]

@acceler9 Yes, I edited down to under 5 mins for the contest! This is the directors cut version!

[dave-d]

Thanks Dave. Interesting phenomenon. Quite surprised to see an electronics engineer wearing a metal strapped wrist watch though! Nice and conductive! Got rid of all my blings years ago. Keep up the good work mate. Great channel.

[yanava]

This could be happening to boards too. That's the reason because most audio boards still use electrolytic capacitors. There are several ways to avoid that with ceramic capacitors. One is to properly lay out the capacitors along regions that won't bend or vibrate under use. Another way is using dampening materials on mounting points. Microphony can also be a problem.

[leopeters]

8:18 is a bit 50 shades of grey-like - i mean: what did the probe or the table do to you? ;)

[EEVblog]

@maxsnts No, try it with a fixed x10 probe with no switch.

[EEVblog]

@nodariel I played drum sticks with the probe, that's kinda a dead giveaway.

[EEVblog]

@yanava Yes, it sure does happen to boards too. It's a real problem in many industries.

[nodariel]

@EEVblog I didnt mean to critcise, it was just an observation. It's a very interesting concept that ceramic capacitors are prone to the piezo-electric effect and has definitely inspired me and I think many others to investigate this further.

[EEVblog]

@WhatsABoyToDo I've said it many times, the Element 14 sites sucks on so many levels. They have been actively trying to be all the bloggers to contribute material to it, without much success. Talked about this a lot on TheAmpHour radio show.

[EEVblog]

@Steaphany I've already done two blogs on job interview tips for EE's

[nodariel]

Could it perhaps be the oscilloscope? Have you tried acoustically isolating the oscilloscope from the bench?

[ciprianwinerElectronicManiac]

please do a blog about LED's that produce voltage when a bright light it's facing the led

[jennyminskey]

Hello, I have a high frequency noise in my home. What instrument can I use to locate where it is coming from?

[DMStern]

You missed the opportunity to include a sponsored link for replacement probes for people who'll bang their ones a bit too hard against the desk.

[mouseminer]

It is the EMF generated into the probe and wire by moving into surrounding magnetic field.

[superdau]

Ahh, one has to love ceramic capacitors. I had some larger (over 2cm diameter) disc capacitors, that could almost be used as speakers!