EEVblog #855 - Ceramic Capacitor Piezoelectric Effect

[EEVblog]

Dave investigates the piezoelectric effect in multi layer chip capacitors (MLCC's). In this case, on the backlight inverter on his own BM235 multimeter.

http://www.hycontek.com/attachments/LCD/DS-HY2613_TC.pdf

[ruffy91]

I didn't watch the video yet, but an interesting usage of high-capacitance X7R MLCCs is as micro-actuators: http://www.theiet.org/resources/journals/eletters/5007/nano-scale-mega-scope.cfm

[Barny]

Wouldn't be a blob of hot glue be a fix to?
The aditional mass would reduce the noice too.
Or am I wrong?

[MarvinTheMartian]

Wouldn't be a blob of hot glue be a fix to?

I in effect asked that too, but no-one responded.

It's not really a 'fix' as such (it doesn't resolve the design fault/parts selection issue) - it is more of a possible work around for those of us less experienced in circuit design and fault finding (ie yours truly )

Loved the explanation Dave and it gives me confidence to replace the cap concerned (if and when I get an appropriate cap). Will give me some more experience with re-working SMDs (where have those stronger glasses gone?  ).

[EEVblog]

Wouldn't be a blob of hot glue be a fix to?

Likely just attenuate it, which might be good enough of course.
The vibration is happening inside the cap and it's likely being amplified by the PCB itself.

[Muttley Snickers]

Would the act of just adding those temporary test wires alter the amplitude or the ringing frequency of the DUT  to any great extent ?.

Mine is due for a thorough modification service tomorrow.....

[bktemp]

The vibration is happening inside the cap and it's likely being amplified by the PCB itself.

The capacitor itself makes almost no noise. That's the same reason why piezo speakers are always mounted in some case or glued to some other plates to have a larger moving surface.
When searching for the culprit capacitor I am using tweezers to amplify the sound the same way the needle of a record player works:
I put one tip onto the capacitor while pressing onto the other end. This allows the tweezers to vibrate feely like a tuning fork.

[Artlav]

So... What's the point of these multimeters if it's just a re-branded unit that you "don't have a schematic of", as said in this video?

[wraper]

So... What's the point of these multimeters if it's just a re-branded unit that you "don't have a schematic of", as said in this video?

Earning money by selling a decent product?

[Muttley Snickers]

It's the vibe, and the squeal but mostly the vibe.

[Brumby]

[timgiles]

I was hoping a pair of Tantalums would be ok, just ordered two Kemet SMD Tantalum Capacitor 35V SMT (3 Packs) 1 and 10uF.

[Barbossa404]

This reminds me of http://thume.ca/screentunes/ (https://github.com/trishume/screentunes for a description), which uses patterns on the screen to generate a modulated and surprisingly loud humming on most lcd screens (led backlight preferred). Same effect but most people don't expect a whining pc screen after they replaced their CRTs 

[idpromnut]

Thanks for the video Dave!    I was going to do a follow-on video trying to mic the sound from my unit, as even with C44 removed, I can still hear a very very faint whine coming from somewhere (only with the case open, and even then it's faint), probably from C43. Excellent scope captures; that is probably something I should have worked on for my video.

Also nice to hear the IRC channel mentioned

[Fungus]

Are you going to include a replacement cap with every meter?

 

[max666]

What about flip it 90 degrees? So the vibrating axis will not be stretching the PCB.

I'm curious as well how flipping the cap would affect this issue.

[Radio Tech]

I quite enjoyed that Dave.   

[EEVblog]

So... What's the point of these multimeters if it's just a re-branded unit that you "don't have a schematic of", as said in this video?

I like the meter, I want to sell it, I think it's good enough to put my name on it, I think it's cool to have a meter I can use in my video that has my brand on it, a lot of people get a kick out of having an EEVblog branded meter, and it helps feed my family. Is there anything wrong with that?
If you don't want to buy one from me that's fine, buy the regular BM235 (I deliberately didn't hide the fact that it's the same as the regular BM235). If you do want to buy one from me with the EEVblog name on it, then great, here it is. If you think its crap, that's fine too. Name an equivalent model meter on the market that you can officially get the schematic of.

[EEVblog]

even with C44 removed, I can still hear a very very faint whine coming from somewhere (only with the case open, and even then it's faint), probably from C43.

Not probably, 100% certainty. There is nothing else in the backlight circuit.

[woox2k]

I can use in my video that has my brand on it,

Nothing wrong with that but i hope you will not choose to use that meter just for that fact even though you might have better meters around that would do the task a bit better. At least i would still like to see real examples where some high-end DMM's do a better task. Thing i'm asking is not to over-advertise it (not saying you do it now, just don't start doing it) 
That said, i would gladly pay a bit more for a DMM knowing that some of that goes directly to you, seeing it "over-advertised" on the video would not change the fact at all.

By the way, where is the unofficial EEVBlog IRC channel you mentioned in the video?

[idpromnut]

By the way, where is the unofficial EEVBlog IRC channel you mentioned in the video?

In #eevblog on Afternet https://www.afternet.org/

[lapm]

So... What's the point of these multimeters if it's just a re-branded unit that you "don't have a schematic of", as said in this video?

Its the official EEVBLOG merchandise... It has Logo on it... There's people that buy directional audio cables, this multimeter is much better purchase and support out favorite video blogger about electronics.
 

[dentaku]

One squeaky thing that annoys me is Indiglow like I have on my Timex watch. It squeaks quite loudly just like that capacitor.
I once saw a remote control that had a light-up face that would activate whenever it was moved. I couldn't stand it 

[arekm]

What's the best approach to find "guilty" part if you have board with tons of capacitors, coils etc - like some laptop mainboard? Using ear doesn't work, too high frequency, so unable to locate.

[Artlav]

Is there anything wrong with that?

Nope, perfectly fine.
I just got an impression over the last few videos that you made your own multimeter (you kept mentioning a "secret project" here and there for the past few months) and the illusion went splat on this video.

[Neilm]

What's the best approach to find "guilty" part if you have board with tons of capacitors, coils etc - like some laptop mainboard? Using ear doesn't work, too high frequency, so unable to locate.

As a first pass, I have used a piece of paper rolled into a tube.

[wraper]

Is there anything wrong with that?

Nope, perfectly fine.
I just got an impression over the last few videos that you made your own multimeter (you kept mentioning a "secret project" here and there for the past few months) and the illusion went splat on this video.

There will be true eevblog meter. This Brymen meter has nothing to do with it.

[strangersound]

What's the best approach to find "guilty" part if you have board with tons of capacitors, coils etc - like some laptop mainboard? Using ear doesn't work, too high frequency, so unable to locate.

As a first pass, I have used a piece of paper rolled into a tube.

Not a bad idea. 

One can also get test microphones (usually electret condensors) with extremely wide frequency ranges (1Hz-200kHz) that I would guess you could use to zero in on a sound source by sweeping it in close range across the board.
ref:
http://www.aco-japan.co.jp/eng/Meas-Mic/meas_mic.html
http://bertrik.sikken.nl/bat/mics.htm

There are also a number of web articles and even a thread in here somewhere about how to use a mic with an oscilloscope.

[Barny]

Another methode is the "pokeing methode"

Use an hard, isulated object like a wooden spoon,... and press towards possible noice source.
If it gets silent or the frequency changes, the culprit is found.

Another way is to press a ear towards the wooden spoon while pokeing around.
That helps to identify different noice sources.

[nwvlab]

even with C44 removed, I can still hear a very very faint whine coming from somewhere (only with the case open, and even then it's faint), probably from C43.

Not probably, 100% certainty. There is nothing else in the backlight circuit.

Couldn't be the remaining faint whine coming from the piezo buzzer, getting some signal (well, the electrical noise from the charge pump) through cross-talk? (or due to poor bypassing)

[MobileWill]

Thanks for the great video. I got a chance to use the meter last night for a new project and hadn't noticed till I bent over my workbench with my ear closer to the meter. You published the video just in time. I think in my case I will just leave it alone. I can't hear it unless I have my ear up to it. Which shouldn't be often.

Great learning experience though.

[Fungus]

What's the best approach to find "guilty" part if you have board with tons of capacitors, coils etc - like some laptop mainboard? Using ear doesn't work, too high frequency, so unable to locate.

Get a piece of tubing. Put one end in your ear and the other end on the suspect component.

(like a stethoscope...)

[Fungus]

Is there anything wrong with that?

Nope, perfectly fine.
I just got an impression over the last few videos that you made your own multimeter (you kept mentioning a "secret project" here and there for the past few months) and the illusion went splat on this video.

That's a different meter, still in the pipeline.

[SilverSolder]

What's the best approach to find "guilty" part if you have board with tons of capacitors, coils etc - like some laptop mainboard? Using ear doesn't work, too high frequency, so unable to locate.

Mechanics use a stethoscope with a solid steel rod to locate noisy bearings etc. in engines, it might be good for finding noisy electronic components as well (maybe after wrapping the rod with some heat shrink to insulate it!).

Example:  http://www.harborfreight.com/mechanics-stethoscope-69913.html

[Brumby]

Mechanics use a stethoscope with a solid steel rod to locate noisy bearings etc. in engines

I actually have one of those.  I might see if I can dig it out and try it on my 235.

[f4eru]

You can use that :
https://product.tdk.com/info/en/catalog/datasheets/mlcc_automotive_megacap_en.pdf

or put the cap on two little wires

or put cutouts in the PCB around the cap...

etc...

[Brumby]

or put the cap on two little wires

That's what ran through my mind ... compliant mounting.

[hopski]

or put the cap on two little wires

That's what ran through my mind ... compliant mounting.

Yeah, but if you wanted do it right then you'd have to seal it in a glass bubble and pump all the air out.   

[vsboost]

So... What's the point of these multimeters if it's just a re-branded unit that you "don't have a schematic of", as said in this video?

I like the meter, I want to sell it, I think it's good enough to put my name on it, I think it's cool to have a meter I can use in my video that has my brand on it, a lot of people get a kick out of having an EEVblog branded meter, and it helps feed my family. Is there anything wrong with that?
If you don't want to buy one from me that's fine, buy the regular BM235 (I deliberately didn't hide the fact that it's the same as the regular BM235). If you do want to buy one from me with the EEVblog name on it, then great, here it is. If you think its crap, that's fine too. Name an equivalent model meter on the market that you can officially get the schematic of.

I definitely get a kick out of owning an EEVBlog product, i posted a pic of it in use on a facebook group I'm a member of regarding SDR's and a few people noticed the meter and mentioned Dave (just goes to show how popular you are lol) Also the meter is fantastic and so accurate compared to the other cheap ones i have been using for years and has an awesome feature set.

I also purchased it because i get hours of FREE entertainment from Dave's videos and i like to show my support.

[rrinker]

or put the cap on two little wires

That's what ran through my mind ... compliant mounting.

Yeah, but if you wanted do it right then you'd have to seal it in a glass bubble and pump all the air out.   

 Would that then make it a vacuum tube voltmeter?

[HAL-42b]

Would that then make it a vacuum tube voltmeter?

  I'd buy that.

[Barny]

What's the best approach to find "guilty" part if you have board with tons of capacitors, coils etc - like some laptop mainboard? Using ear doesn't work, too high frequency, so unable to locate.

Mechanics use a stethoscope with a solid steel rod to locate noisy bearings etc. in engines, it might be good for finding noisy electronic components as well (maybe after wrapping the rod with some heat shrink to insulate it!).

Example:  http://www.harborfreight.com/mechanics-stethoscope-69913.html

To use a metal rod with an electronic component isn't a good idea.
Thats why I use an wooden spoon (and hope I dond get cought for abuse cooking utensils) or a wooden rod.

[f4eru]

To use a metal rod with an electronic component isn't a good idea.
Thats why I use an wooden spoon (and hope I dond get cought for abuse cooking utensils) or a wooden rod.

You can glue a ceramic pellet at the end to isolate it electrically while still transmitting vibrations...

[mc349iii]

Did anyone try soldering a LED to the empty pad?  Seen early in the video.   Presumably that's the serial output signal,  it would be nice if there is a signal being sent.

[Brumby]

Would that then make it a vacuum tube voltmeter?

  I'd buy that.

+1      

[fanOfeeDIY]

Hi,

I am basically earning my income with software engineering area but I used to work for Japanese Manufacturing company and experienced the sound of Ceramic Capacitor.

Major companies of Ceramic Capacitor have web pages for this effect and provide capacitor series with less effect.

Murata
http://www.murata.com/en-global/products/capacitor/mlcc/solution/naki
(Video is kind of Jinglish)

Taiyo Yuden
http://www.yuden.co.jp/ut/product/tech/faq/q018.html

TDK
https://product.tdk.com/info/en/products/capacitor/ceramic/mlcc/technote/solution/mlcc02/index.html

[SeanB]

Compliant mounting ( blob of acetoxy free electronics grade silicone)  on the capacitor, or simply using a different manufacturers part ( or even a different batch) will probably lower the noise, along with using a different capacitor type, a small film unit might fit, or a PCB mount electrolytic using the same pad spacing.

[Bud]

What's the best approach to find "guilty" part if you have board with tons of capacitors, coils etc - like some laptop mainboard? Using ear doesn't work, too high frequency, so unable to locate.

Perhaps use another shitty ceramic capacitor wired to a scope or audio amplifier. Tape the wires to a cotton swab rod with the cotton part cut or to a sushi chopstick  to make a probe

[EEVblog]

Is there anything wrong with that?

Nope, perfectly fine.
I just got an impression over the last few videos that you made your own multimeter (you kept mentioning a "secret project" here and there for the past few months) and the illusion went splat on this video.

You are not a supporter who's "in the know" 

[Fungus]

Have you shown this video to Brymen? If so, what did they say...?   

[modrobert]

Feature: * Subtle high pitched indicator sound when the backlight is on, as a reminder, to preserve battery life.

[hopski]

It does turn itself off after 10 minutes to save battery life. seems a bit long, maybe that could be reduced.

[tszaboo]

So another industry story from the same effect:
We had an instrument, measuring voltages with some 0.003% accuracy, with some kHz speed. So obviously, it had a precision reference voltage, which was filtered quite a lot. The issue was, that it was picking up any vibration of the PCB, and there were fans in the system (loud ones). So I traced down the issue to the ceramic capacitors filtering the reference voltage. There was a PI filter,  CRC, 10 uF, 10Kohm, 10uF (from the top of my head) on the output of the reference voltage, X7R capacitors. That is an 1 Hz filter, going to an opamp for buffering. So when I tapped the capacitors with a pen, they were creating up to a few mV  (!) of noise on the output. That is how much noise these can generate.
The caps were replaced with SMD film capacitors. Spare no expense. All the noise was gone, I could hammer those all day long. I guess that was lesson learned.

[artag]

One can also get test microphones (usually electret condensors) with extremely wide frequency ranges (1Hz-200kHz) that I would guess you could use to zero in on a sound source by sweeping it in close range across the board.
ref:
http://www.aco-japan.co.jp/eng/Meas-Mic/meas_mic.html
http://bertrik.sikken.nl/bat/mics.htm

There are also a number of web articles and even a thread in here somewhere about how to use a mic with an oscilloscope.

Or you could use a small ceramic multilayer cap as a microphone. It's not made to pick up sound from the air so it should be more selective for mechanical contact. Don't forget that the actual guilty device may not be the 'loudest' place - that might be the circuit board node or other component that's moving as a result of the vibration.

[wraper]

you could use a small ceramic multilayer cap as a microphone.

Nope you couldn't. That would be an awful microphone, which wouldn't be able to sense anything but a huge vibration.

[elCap]

The big inductor on the back side of the PCB is for the piezo buzzer.
In my Brymen 257s the buzzer did not work when I first got it. I didn't bother to return it for warranty repair.
After I had the meter resting on top of my power supply, heating it a little, it suddenly started to work. Took the meter apart, and found that there was a small crack in the inductor. After replacing it the buzzer started to work. I didn't have the big value needed so the volume is a bit on the low side now.
So if one wants a higher volume from the buzzer, install a bigger value inductor.

[Muttley Snickers]

I think that Dave mentioned that the inductor on the rear of the BM-235 board was for the Non Contact EF Detection which according to both the BM-235 and the BM-257 manuals is located on the top right hand side of both meters as shown in the picture below.

[elCap]

I didn't completely trace out the circuit but I'm quite sure the inductor (L4 in BM-257) is part of the buzzer circuit as replacing it fixed my non-working buzzer.
First image that came up from a google search for a piezo buzzer circuit:
http://2.bp.blogspot.com/-9Db008ehTHA/Tul-pu7SF8I/AAAAAAAAATU/r7wYX7CdL5U/s1600/12+Volt+Piezo+Buzzer+Circuit+Diagram.png

[Barny]

Could it be, that the inductor gets used for both purposes?

Makeing noise and detect ?

[Godzil]

I've checked with my BM257s, with my ear stuck on it without the backlight, I can hear a really really fait buzzing that slightly change with the backlight is on, but as the backlight is not white, the voltage is probably lower, the design is different so not really an interesting test after all, but mine is faintly buzzing even without the backlight

[iXod]

If room permits, replace with different composition cap? Electro SMD or radial (laid on side)? I've seen some pretty small radials...

Or poly-something?

That should eliminate the issue, no?

[cte7ds]

Checked my Brymen BM869 and BM189. Couldn't hear anything in a quiet room with the backlights turned on and my ear pressed against the backs. 

However, I've gotten (and keep on getting) my fair share of this problem, thanks to Logitech... (https://www.eevblog.com/forum/repair/ceramic-capacitor-whine-in-logitech-g-series-mice/) 

[Georgitsu]

This was great! I noticed a similar high-pitched squeal on a instrument I was designing, but I didn't know what it was from. First I thought it was from the speaker output, but later discovered this piezo-electric effect of certain capacitors and realized that was surely the cause.

Cool video! 

[Synthetase]

I've checked with my BM257s, with my ear stuck on it without the backlight, I can hear a really really fait buzzing that slightly change with the backlight is on, but as the backlight is not white, the voltage is probably lower, the design is different so not really an interesting test after all, but mine is faintly buzzing even without the backlight

Yep, I tried exactly the same thing, same result.

[EEVblog]

Have you shown this video to Brymen? If so, what did they say...?   

Got word back from Brymen R&D. Cap has been changed from 10uF to 10nF, problem solved. Guess they didn't really need that 10uF after all.
All new units I get will be fixed.

[WackyGerman]

Got word back from Brymen R&D. Cap has been changed from 10uF to 10nF, problem solved. Guess they didn't really need that 10uF after all.
All new units I get will be fixed.
[/quote]

 

[Godzil]

Have you shown this video to Brymen? If so, what did they say...?   

Got word back from Brymen R&D. Cap has been changed from 10uF to 10nF, problem solved. Guess they didn't really need that 10uF after all.
All new units I get will be fixed.

They are a good brand, and I'm really happy to have discovered them from your video, I really love my 257S (and thanks to Frankie for selling them!)

[jancelot]

Would it be possible to replace the ceramic capacitor to totally eliminate the sound?
EDITED: yes it's possible watch until the end of the video.

By the way, the Brymen Bm257s makes a very low noise in the audible range, if you put the ear in the right side of the screen (as you look at it), with either the screen backlight on or off.