charge-based piezo drive

> How deep a notch do you need?  

Several times 1/Q. You want the open loop gain at the resonance to be well below 1.

You also want the notch to be sharp, so that its phase funnies don't extend too low in frequency.

Cheers

Phil Hobbs
 
On a sunny day (Mon, 15 Jul 2019 10:09:11 -0500) it happened amdx
<nojunk@knology.net> wrote in <qgi4un$ui2$1@dont-email.me>:

On 7/15/2019 1:17 AM, Jan Panteltje wrote:
On a sunny day (Sun, 14 Jul 2019 15:48:20 -0500) it happened amdx
nojunk@knology.net> wrote in <qgg4eo$14i$1@dont-email.me>:

On 7/14/2019 1:13 PM, Jan Panteltje wrote:
On a sunny day (14 Jul 2019 10:37:47 -0700) it happened Winfield Hill
winfieldhill@yahoo.com> wrote in <qgfp9b0f1s@drn.newsguy.com>:

I'm finishing a section on charge-based piezo
drive. Anybody want to say anything about it?

What is a 'charge based' piezo drive?

I am driving some big 40 kHz piezos hard with a MOSFET push pull circuit
and transformer, PIC as signal generator.
These:
https://www.ebay.com/itm/400728340024
2 pieces, 120W total, from 12V DC.


When I worked at a small company called Ultrasonic Energy Systems.
We drove a 2" round x 0.80" thick PZT8 ceramic bonded to a 1/16"
aluminum plate at 1000 watts pulsed and 250 continuous.
We also had it in an ice water bath. to keep the transducer cool.
We ran the transducers around 660kHz, whereever the maximum efficiency
was. We treated solution in a vessel through an FEP Teflon 0.003" window.
One of our customers substituted PTFE for the FEP window and could not
repeat results. He has killing bacteria in milk, after the teflon sub,
his kill rate went way down.
FUN fact; we could watch sonoluminescence go across a 20" aquarium,
reflect off the glass go to the other end and reflect
again before dying off.
First design was a class A amplifier, second one we used class E.
The class E driver design was stupid, we had an osc and a couple of
tuned preamps, to drive four Mosfets. By then there were good mosfet
drivers, the tuned circuits were a PITA, I was the one winding coils and
transformers.
Probably OK for a physicist designing electronics. (Not me)
Our claim to fame was the sale of a 4000 watt unit to Cal Tech,
it used 4- 4" x 4" ceramics, with about a 1 gallon flow through
treatment vessel.
I remember those years fondly.
Mikek


I always wanted to do that sonoluminescence experiment,
but am a bit afraid of all that high power 40 kHz for my ears.

The PIC I programmed for this does at start up do a range of frequency increments,
At the same time it measures output voltage for each frequency and remembers the best one
representing resonance.

I don't recall why, but we ran our transducers at anti-resonance, as I
said my boss was in acoustics from the start, did navy soar, several
ultrasonic companies, one time said he took a job just to find out if
the people in the company knew what he knew. He even specified how to
pole his ceramics. (all above me). It seems driving at anti-resonance
might have been something about the beam shape, but I could be wrong, he
held some things secret.
Click to expand...

I dunno what he means by that either.
I have played quite a bit with ceramic transducers, remember in the old days
TV remotes used ultrasonics, so I had a few from my repair days,
and you can do a lot of fun things with those,
connect to a tuned circuit etc.. measure wind speed:
http://panteltje.com/pub/wind_speed_by_differential_2_ebay_distance_meters_IMG_4891.JPG
http://panteltje.com/pub/acoustic_wind_speed_phase_only_test_setup_IMG_4887.JPG
the last one if from old remotes...
I also did some Doppler stuff, very sensitive motion detection..
could detect if you blinked an eye

Here test with 2 small 44 kHz transducers in a 'wind tunnel', see the phase shift
between transmitter and receiver (a few cm away) change as I increase the airflow (PC fan not in picture
blowing through the 'tunnel' (cardboard tube) ),
you can see the vane moving indication wind speed.
44kHz_Doppler_phase_change_in_wind_tunnel_with_vane_MVI_4113.AVI



After tuning out the capacitance we were left with about 20 ohms of
resistance to drive. He built the transducers, had a hot plate and
pneumatic press to apply pressure while the epoxy cured under heat. I
recall he used a sheet conductive epoxy 0.004" thick, but always said
the gauze in the sheet reduced the efficiency of his transducers.
We sorted the ceramics to find what he expected to be the best, had a
lot of duds, then when he built the transducer we tested it's
efficiency. If it was not over 80%, he would build another. Don't
remember his cutoff, just know it was over 80%.
I don't recall if you are in the states, if you are, and want to
experiment with a high frequency ceramic I could send you a couple.
My email is good.
Click to expand...

Very kind of you, no I am in Europe, Netherlands.
But really that high a frequency is beyond my current interest,
also I am flooded with experiments that I somehow have to get going if ever,,,
But I really appreciate the offer, if I ever think of some application
I will email you for sure.
The sonoluninescence can also be done with the transducers I have,
there is even a youtube video from somebody who did just that:
https://www.youtube.com/watch?v=m-O7dS2tYsg


You would need to bond it to an aluminum plate, and build the amp to
drive it. I think I have some ceramics to build 660kHz and some 440kHz
transducers. I don't know the numbers, but it has to do with the speed
of sound in the aluminum and the thickness of it and the ceramic and 1/2
waves. I do recall the ceramics we built 660kHz transducers with had a
resonance at about 1.2MHz and after bonding to 1/16" aluminum it dropped
to 660kHz. I don't recall the aluminum thickness for the 440kHz
transducer faceplate.
When the boss quit, he left everything in the building, I knew the
landlord and bought a lot of it cheap just because he was throwing it
out. I wish I gotten there sooner, I missed some stuff I wanted.
I tried to get the boss to write a book before he died, he didn't and
he did pass.
Let me know if you want ceramics.

Mikek

BTW, here's a link to some pictures of how we cooled the transducer
while allowing the solution to avoid contamination from the aluminum
faceplate. Transducer housing is 4" in diameter.

https://web.archive.org/web/20060127221627/http://www.ultrasonic-energy.com/accessories.html
Click to expand...

Interesting.
 
On 2019-07-15 8:09 a.m., Phil Hobbs wrote:
On 7/14/19 2:32 PM, Martin Riddle wrote:
On Sun, 14 Jul 2019 18:13:49 GMT, Jan Panteltje
pNaOnStPeAlMtje@yahoo.com> wrote:

On a sunny day (14 Jul 2019 10:37:47 -0700) it happened Winfield Hill
winfieldhill@yahoo.com> wrote in <qgfp9b0f1s@drn.newsguy.com>:

I'm finishing a section on charge-based piezo
drive.  Anybody want to say anything about it?

What is a 'charge based' piezo drive?

I am driving some big 40 kHz piezos hard with a MOSFET push pull circuit
and transformer, PIC as signal generator.
These:
https://www.ebay.com/itm/400728340024
2 pieces, 120W total, from 12V DC.

The piezo is capacitive. I'm assuming Win is treating it like a Mosfet
gate (Qg), and designing the driver so that the piezo mechanically
oscillates in as little time as the driver can handle.

You sense the integrated charge and feed back on that.  Conceptually
like running the piezo with a very small capacitor in series, and
jacking up the drive voltage.

Of course you have to get the DC from someplace, but that can be a
capacitive gauge or something like that--much slower than the piezo. The
reason that charge control is a good idea is that it reduces the
nonlinearity and hysteresis of the piezo actuator, so you can get better
control over a wider displacement range.

One way of looking at it is that the capacitance goes down as the piezo
material starts to saturate, so an increment of charge dq produces a
larger voltage change dV, helping compensate the nonlinearity.
Click to expand...

Hi,

Another way to view it is that capacitance is more closely coupled to
the piezo crystal length than the drive voltage is coupled to the
piezo crystal length, ie fewer external factors change the capacitance
than the voltage. It would be interesting to see all the various
external factors (temperature etc) related to feedback signals to get
more accurate positioning.

cheers,
Jamie


There's an analogous process that reduces hysteresis, but I'm less clear
on how that works.

Cheers

Phil Hobbs
Click to expand...
 
On 7/15/2019 11:51 AM, Jan Panteltje wrote:
On a sunny day (Mon, 15 Jul 2019 10:09:11 -0500) it happened amdx
nojunk@knology.net> wrote in <qgi4un$ui2$1@dont-email.me>:

On 7/15/2019 1:17 AM, Jan Panteltje wrote:
On a sunny day (Sun, 14 Jul 2019 15:48:20 -0500) it happened amdx
nojunk@knology.net> wrote in <qgg4eo$14i$1@dont-email.me>:

On 7/14/2019 1:13 PM, Jan Panteltje wrote:
On a sunny day (14 Jul 2019 10:37:47 -0700) it happened Winfield Hill
winfieldhill@yahoo.com> wrote in <qgfp9b0f1s@drn.newsguy.com>:

I'm finishing a section on charge-based piezo
drive. Anybody want to say anything about it?

What is a 'charge based' piezo drive?

I am driving some big 40 kHz piezos hard with a MOSFET push pull circuit
and transformer, PIC as signal generator.
These:
https://www.ebay.com/itm/400728340024
2 pieces, 120W total, from 12V DC.


When I worked at a small company called Ultrasonic Energy Systems.
We drove a 2" round x 0.80" thick PZT8 ceramic bonded to a 1/16"
aluminum plate at 1000 watts pulsed and 250 continuous.
We also had it in an ice water bath. to keep the transducer cool.
We ran the transducers around 660kHz, whereever the maximum efficiency
was. We treated solution in a vessel through an FEP Teflon 0.003" window.
One of our customers substituted PTFE for the FEP window and could not
repeat results. He has killing bacteria in milk, after the teflon sub,
his kill rate went way down.
FUN fact; we could watch sonoluminescence go across a 20" aquarium,
reflect off the glass go to the other end and reflect
again before dying off.
First design was a class A amplifier, second one we used class E.
The class E driver design was stupid, we had an osc and a couple of
tuned preamps, to drive four Mosfets. By then there were good mosfet
drivers, the tuned circuits were a PITA, I was the one winding coils and
transformers.
Probably OK for a physicist designing electronics. (Not me)
Our claim to fame was the sale of a 4000 watt unit to Cal Tech,
it used 4- 4" x 4" ceramics, with about a 1 gallon flow through
treatment vessel.
I remember those years fondly.
Mikek


I always wanted to do that sonoluminescence experiment,
but am a bit afraid of all that high power 40 kHz for my ears.

The PIC I programmed for this does at start up do a range of frequency increments,
At the same time it measures output voltage for each frequency and remembers the best one
representing resonance.

I don't recall why, but we ran our transducers at anti-resonance, as I
said my boss was in acoustics from the start, did navy soar, several
ultrasonic companies, one time said he took a job just to find out if
the people in the company knew what he knew. He even specified how to
pole his ceramics. (all above me). It seems driving at anti-resonance
might have been something about the beam shape, but I could be wrong, he
held some things secret.

I dunno what he means by that either.
Click to expand...

Not clear about the question, you don't know anti-resonance or you don't
know why run the transducer at anti-resonance?
Maybe as simple as easier to drive 20 ohms, maybe beam shape, maybe less
susceptibility to reflections causing impedance variations. That last
one seems very likely, I remember measuring impedance and watching it
swing up and down as you got closer to a reflector. If my math is
correct, the impedance would go from high to low just by moving the
reflector 1mm.


I have played quite a bit with ceramic transducers, remember in the old days
TV remotes used ultrasonics, so I had a few from my repair days,
and you can do a lot of fun things with those,
connect to a tuned circuit etc.. measure wind speed:
http://panteltje.com/pub/wind_speed_by_differential_2_ebay_distance_meters_IMG_4891.JPG
http://panteltje.com/pub/acoustic_wind_speed_phase_only_test_setup_IMG_4887.JPG
the last one if from old remotes...
I also did some Doppler stuff, very sensitive motion detection..
could detect if you blinked an eye

Here test with 2 small 44 kHz transducers in a 'wind tunnel', see the phase shift
between transmitter and receiver (a few cm away) change as I increase the airflow (PC fan not in picture
blowing through the 'tunnel' (cardboard tube) ),
you can see the vane moving indication wind speed.
44kHz_Doppler_phase_change_in_wind_tunnel_with_vane_MVI_4113.AVI



After tuning out the capacitance we were left with about 20 ohms of
resistance to drive. He built the transducers, had a hot plate and
pneumatic press to apply pressure while the epoxy cured under heat. I
recall he used a sheet conductive epoxy 0.004" thick, but always said
the gauze in the sheet reduced the efficiency of his transducers.
We sorted the ceramics to find what he expected to be the best, had a
lot of duds, then when he built the transducer we tested it's
efficiency. If it was not over 80%, he would build another. Don't
remember his cutoff, just know it was over 80%.
I don't recall if you are in the states, if you are, and want to
experiment with a high frequency ceramic I could send you a couple.
My email is good.

Very kind of you, no I am in Europe, Netherlands.
But really that high a frequency is beyond my current interest,
also I am flooded with experiments that I somehow have to get going if ever,,,
But I really appreciate the offer, if I ever think of some application
I will email you for sure.
The sonoluninescence can also be done with the transducers I have,
there is even a youtube video from somebody who did just that:
https://www.youtube.com/watch?v=m-O7dS2tYsg
Click to expand...

I don't see where he has sonoluminesence. Generally you must dark
accustom your eyes because it is a weak light. and it is light blue in
color maybe moving towards green, but mostly blue as I recall, it's been
20 years. When I saw it it was from our 2" transducer, and a 2" beam of
light zigzaged from aquarium end to aquarium end.
Also with high frequency (40kHz vs 660kHz) you can get about ten times
more power into the water solution before cavitation starts. And bubble
size starts out 1/66 as big for high frequency.
Just regurgitating as I remember things, sorry.



You would need to bond it to an aluminum plate, and build the amp to
drive it. I think I have some ceramics to build 660kHz and some 440kHz
transducers. I don't know the numbers, but it has to do with the speed
of sound in the aluminum and the thickness of it and the ceramic and 1/2
waves. I do recall the ceramics we built 660kHz transducers with had a
resonance at about 1.2MHz and after bonding to 1/16" aluminum it dropped
to 660kHz. I don't recall the aluminum thickness for the 440kHz
transducer faceplate.
When the boss quit, he left everything in the building, I knew the
landlord and bought a lot of it cheap just because he was throwing it
out. I wish I gotten there sooner, I missed some stuff I wanted.
I tried to get the boss to write a book before he died, he didn't and
he did pass.
Let me know if you want ceramics.

Mikek

BTW, here's a link to some pictures of how we cooled the transducer
while allowing the solution to avoid contamination from the aluminum
faceplate. Transducer housing is 4" in diameter.

https://web.archive.org/web/20060127221627/http://www.ultrasonic-energy.com/accessories.html

Interesting.
Click to expand...
 
On Monday, July 15, 2019 at 2:17:27 AM UTC-4, Jan Panteltje wrote:
On a sunny day (Sun, 14 Jul 2019 15:48:20 -0500) it happened amdx
nojunk@knology.net> wrote in <qgg4eo$14i$1@dont-email.me>:

On 7/14/2019 1:13 PM, Jan Panteltje wrote:
On a sunny day (14 Jul 2019 10:37:47 -0700) it happened Winfield Hill
winfieldhill@yahoo.com> wrote in <qgfp9b0f1s@drn.newsguy.com>:

I'm finishing a section on charge-based piezo
drive. Anybody want to say anything about it?

What is a 'charge based' piezo drive?

I am driving some big 40 kHz piezos hard with a MOSFET push pull circuit
and transformer, PIC as signal generator.
These:
https://www.ebay.com/itm/400728340024
2 pieces, 120W total, from 12V DC.


When I worked at a small company called Ultrasonic Energy Systems.
We drove a 2" round x 0.80" thick PZT8 ceramic bonded to a 1/16"
aluminum plate at 1000 watts pulsed and 250 continuous.
We also had it in an ice water bath. to keep the transducer cool.
We ran the transducers around 660kHz, whereever the maximum efficiency
was. We treated solution in a vessel through an FEP Teflon 0.003" window.
One of our customers substituted PTFE for the FEP window and could not
repeat results. He has killing bacteria in milk, after the teflon sub,
his kill rate went way down.
FUN fact; we could watch sonoluminescence go across a 20" aquarium,
reflect off the glass go to the other end and reflect
again before dying off.
First design was a class A amplifier, second one we used class E.
The class E driver design was stupid, we had an osc and a couple of
tuned preamps, to drive four Mosfets. By then there were good mosfet
drivers, the tuned circuits were a PITA, I was the one winding coils and
transformers.
Probably OK for a physicist designing electronics. (Not me)
Our claim to fame was the sale of a 4000 watt unit to Cal Tech,
it used 4- 4" x 4" ceramics, with about a 1 gallon flow through
treatment vessel.
I remember those years fondly.
Mikek


I always wanted to do that sonoluminescence experiment,
but am a bit afraid of all that high power 40 kHz for my ears.
Click to expand...
Jan, one hint about sonoluminescence. The water has to have to air taken
out of it. We did this by boiling the water, then cooling it (with cap on)
And then you've got an hour or so till the air diffuses back in.
PITA of an experiment, and not really worth much over the 'Gee- Whiz'
factor.

George H.
The PIC I programmed for this does at start up do a range of frequency increments,
At the same time it measures output voltage for each frequency and remembers the best one
representing resonance.
It then uses that one, takes about a 2 seconds run to find it.
It can do an automatic range of other pings too, is for anti-fauling in boats.

I still have no idea what a 'charge based' piezo drive is?
It is all about resonance AFAIK.

What I find amazing is those little beepers, I have one from China, that make a +120 dB 3 KHz or so beep
hardly using any power, have one as alarm here, you cannot live in that noise.. few mW?
Click to expand...
 
On 7/15/2019 2:49 PM, George Herold wrote:
On Monday, July 15, 2019 at 2:17:27 AM UTC-4, Jan Panteltje wrote:
On a sunny day (Sun, 14 Jul 2019 15:48:20 -0500) it happened amdx
nojunk@knology.net> wrote in <qgg4eo$14i$1@dont-email.me>:

On 7/14/2019 1:13 PM, Jan Panteltje wrote:
On a sunny day (14 Jul 2019 10:37:47 -0700) it happened Winfield Hill
winfieldhill@yahoo.com> wrote in <qgfp9b0f1s@drn.newsguy.com>:

I'm finishing a section on charge-based piezo
drive. Anybody want to say anything about it?

What is a 'charge based' piezo drive?

I am driving some big 40 kHz piezos hard with a MOSFET push pull circuit
and transformer, PIC as signal generator.
These:
https://www.ebay.com/itm/400728340024
2 pieces, 120W total, from 12V DC.


When I worked at a small company called Ultrasonic Energy Systems.
We drove a 2" round x 0.80" thick PZT8 ceramic bonded to a 1/16"
aluminum plate at 1000 watts pulsed and 250 continuous.
We also had it in an ice water bath. to keep the transducer cool.
We ran the transducers around 660kHz, whereever the maximum efficiency
was. We treated solution in a vessel through an FEP Teflon 0.003" window.
One of our customers substituted PTFE for the FEP window and could not
repeat results. He has killing bacteria in milk, after the teflon sub,
his kill rate went way down.
FUN fact; we could watch sonoluminescence go across a 20" aquarium,
reflect off the glass go to the other end and reflect
again before dying off.
First design was a class A amplifier, second one we used class E.
The class E driver design was stupid, we had an osc and a couple of
tuned preamps, to drive four Mosfets. By then there were good mosfet
drivers, the tuned circuits were a PITA, I was the one winding coils and
transformers.
Probably OK for a physicist designing electronics. (Not me)
Our claim to fame was the sale of a 4000 watt unit to Cal Tech,
it used 4- 4" x 4" ceramics, with about a 1 gallon flow through
treatment vessel.
I remember those years fondly.
Mikek


I always wanted to do that sonoluminescence experiment,
but am a bit afraid of all that high power 40 kHz for my ears.
Jan, one hint about sonoluminescence. The water has to have to air taken
out of it. We did this by boiling the water, then cooling it (with cap on)
And then you've got an hour or so till the air diffuses back in.
PITA of an experiment, and not really worth much over the 'Gee- Whiz'
factor.

George H.
Click to expand...

Hi George,
I will have to disagree with you about degassing the water.
We didn't degassed our water and didn't have any problem getting
sonoluminescence. Only differing factor is, we used high frequency,
but I don't think that matters.
In some experiments we added air, (sparge gas) to enhance reactions.
In the link below is a writeup about sparge gases by my boss, Henry.
In it he starts with Ultrasound removal of Carbon Dioxide from water,
but the interesting part is at about 1/3 of they way down where it says,
FEATURED ARTICLE. It talks about using Noble gases as the sparge gas
having increased enhancement of reactions over air.

> https://web.archive.org/web/20060216195024/http://www.ultrasonic-energy.com/shop_talk.html

I have more, but I get tired, maybe tomorrow.

Mikek








The PIC I programmed for this does at start up do a range of frequency increments,
At the same time it measures output voltage for each frequency and remembers the best one
representing resonance.
It then uses that one, takes about a 2 seconds run to find it.
It can do an automatic range of other pings too, is for anti-fauling in boats.

I still have no idea what a 'charge based' piezo drive is?
It is all about resonance AFAIK.

What I find amazing is those little beepers, I have one from China, that make a +120 dB 3 KHz or so beep
hardly using any power, have one as alarm here, you cannot live in that noise.. few mW?
Click to expand...
 
On a sunny day (Mon, 15 Jul 2019 14:27:32 -0500) it happened amdx
<nojunk@knology.net> wrote in <qgik34$230$1@dont-email.me>:

On 7/15/2019 11:51 AM, Jan Panteltje wrote:
On a sunny day (Mon, 15 Jul 2019 10:09:11 -0500) it happened amdx
nojunk@knology.net> wrote in <qgi4un$ui2$1@dont-email.me>:

I dunno what he means by that either.

Not clear about the question, you don't know anti-resonance or you don't
know why run the transducer at anti-resonance?
Click to expand...

'anti resonance' could mean?
[1] Using it out of resonance (that is easy).
[2] Or some magical thing? Then it is bull.
It is either in resonance or it is not, as simple as that.

The sonoluninescence can also be done with the transducers I have,
there is even a youtube video from somebody who did just that:
https://www.youtube.com/watch?v=m-O7dS2tYsg

I don't see where he has sonoluminesence. Generally you must dark
accustom your eyes because it is a weak light. and it is light blue in
color maybe moving towards green, but mostly blue as I recall, it's been
20 years.
Click to expand...

I agree, maybe he just sees the bubbles forming by shining a light through the vessel.
In sonoluminescence AFAIK the bubbles implode and cause a flash of light.

Not sure his bubbles really implode, but at least he has bubbles.
There was a whole lot to do about those collapsing bubbles causing some radiation.
I have plenty of measurement stuff around for that.
But I think that experiment was refuted as radiation came from some other source in their lab.

I stopped following the endless postings about that (in sci.physics ?) long ago.


When I saw it it was from our 2" transducer, and a 2" beam of
light zigzaged from aquarium end to aquarium end.
Also with high frequency (40kHz vs 660kHz) you can get about ten times
more power into the water solution before cavitation starts. And bubble
size starts out 1/66 as big for high frequency.
Just regurgitating as I remember things, sorry.
Click to expand...

OK.

Main reason I am not trying is I need my ears, and I could imagine standing waves forming
in the fluid in my ears,,, destroying nerve cells.

And if it ain't 'nuculear' it is not so interesting anyways.
Where does the light (EM radiation) come from?
Non-linear medium frequency conversion? No too much frequency difference I'd think.
The physics is in a way interesting.
 
On a sunny day (Mon, 15 Jul 2019 12:49:20 -0700 (PDT)) it happened George
Herold <gherold@teachspin.com> wrote in
<e099088b-3f83-4d2c-87c4-3fa287765ef1@googlegroups.com>:

Jan, one hint about sonoluminescence. The water has to have to air taken
out of it. We did this by boiling the water, then cooling it (with cap on)
And then you've got an hour or so till the air diffuses back in.
PITA of an experiment, and not really worth much over the 'Gee- Whiz'
factor.
Click to expand...

OK, got it, thank you.
 
On Monday, July 15, 2019 at 10:23:56 PM UTC-4, amdx wrote:
On 7/15/2019 2:49 PM, George Herold wrote:
On Monday, July 15, 2019 at 2:17:27 AM UTC-4, Jan Panteltje wrote:
On a sunny day (Sun, 14 Jul 2019 15:48:20 -0500) it happened amdx
nojunk@knology.net> wrote in <qgg4eo$14i$1@dont-email.me>:

On 7/14/2019 1:13 PM, Jan Panteltje wrote:
On a sunny day (14 Jul 2019 10:37:47 -0700) it happened Winfield Hill
winfieldhill@yahoo.com> wrote in <qgfp9b0f1s@drn.newsguy.com>:

I'm finishing a section on charge-based piezo
drive. Anybody want to say anything about it?

What is a 'charge based' piezo drive?

I am driving some big 40 kHz piezos hard with a MOSFET push pull circuit
and transformer, PIC as signal generator.
These:
https://www.ebay.com/itm/400728340024
2 pieces, 120W total, from 12V DC.


When I worked at a small company called Ultrasonic Energy Systems.
We drove a 2" round x 0.80" thick PZT8 ceramic bonded to a 1/16"
aluminum plate at 1000 watts pulsed and 250 continuous.
We also had it in an ice water bath. to keep the transducer cool.
We ran the transducers around 660kHz, whereever the maximum efficiency
was. We treated solution in a vessel through an FEP Teflon 0.003" window.
One of our customers substituted PTFE for the FEP window and could not
repeat results. He has killing bacteria in milk, after the teflon sub,
his kill rate went way down.
FUN fact; we could watch sonoluminescence go across a 20" aquarium,
reflect off the glass go to the other end and reflect
again before dying off.
First design was a class A amplifier, second one we used class E.
The class E driver design was stupid, we had an osc and a couple of
tuned preamps, to drive four Mosfets. By then there were good mosfet
drivers, the tuned circuits were a PITA, I was the one winding coils and
transformers.
Probably OK for a physicist designing electronics. (Not me)
Our claim to fame was the sale of a 4000 watt unit to Cal Tech,
it used 4- 4" x 4" ceramics, with about a 1 gallon flow through
treatment vessel.
I remember those years fondly.
Mikek


I always wanted to do that sonoluminescence experiment,
but am a bit afraid of all that high power 40 kHz for my ears.
Jan, one hint about sonoluminescence. The water has to have to air taken
out of it. We did this by boiling the water, then cooling it (with cap on)
And then you've got an hour or so till the air diffuses back in.
PITA of an experiment, and not really worth much over the 'Gee- Whiz'
factor.

George H.

Hi George,
I will have to disagree with you about degassing the water.
We didn't degassed our water and didn't have any problem getting
sonoluminescence. Only differing factor is, we used high frequency,
but I don't think that matters.
In some experiments we added air, (sparge gas) to enhance reactions.
In the link below is a writeup about sparge gases by my boss, Henry.
In it he starts with Ultrasound removal of Carbon Dioxide from water,
but the interesting part is at about 1/3 of they way down where it says,
FEATURED ARTICLE. It talks about using Noble gases as the sparge gas
having increased enhancement of reactions over air.

https://web.archive.org/web/20060216195024/http://www.ultrasonic-energy.com/shop_talk.html

I have more, but I get tired, maybe tomorrow.
Click to expand...
OK thanks Mike. Perhaps the unit we had was under-powered and didn't have
enough to make flashes w/o removing the air.

George H.
Mikek








The PIC I programmed for this does at start up do a range of frequency increments,
At the same time it measures output voltage for each frequency and remembers the best one
representing resonance.
It then uses that one, takes about a 2 seconds run to find it.
It can do an automatic range of other pings too, is for anti-fauling in boats.

I still have no idea what a 'charge based' piezo drive is?
It is all about resonance AFAIK.

What I find amazing is those little beepers, I have one from China, that make a +120 dB 3 KHz or so beep
hardly using any power, have one as alarm here, you cannot live in that noise.. few mW?
Click to expand...
 
On 7/16/2019 1:53 AM, Jan Panteltje wrote:
On a sunny day (Mon, 15 Jul 2019 14:27:32 -0500) it happened amdx
nojunk@knology.net> wrote in <qgik34$230$1@dont-email.me>:

On 7/15/2019 11:51 AM, Jan Panteltje wrote:
On a sunny day (Mon, 15 Jul 2019 10:09:11 -0500) it happened amdx
nojunk@knology.net> wrote in <qgi4un$ui2$1@dont-email.me>:

I dunno what he means by that either.

Not clear about the question, you don't know anti-resonance or you don't
know why run the transducer at anti-resonance?


'anti resonance' could mean?
[1] Using it out of resonance (that is easy).
[2] Or some magical thing? Then it is bull.
It is either in resonance or it is not, as simple as that.
Click to expand...


Ya, you have me wondering if I used the wrong term, but it is the low
impedance point on a an impedance curve.
When I characterized piezos I only looked at the lowest points, but
this curve continues up in frequency, but it shows my point. We used
them at the low impedance point rather that the high impedance point.
https://www.researchgate.net/figure/The-electrical-impedance-curve-of-the-piezoelectric-disc-transducer-used-for-experiments_fig1_324677066
Click to expand...



The sonoluninescence can also be done with the transducers I have,
there is even a youtube video from somebody who did just that:
https://www.youtube.com/watch?v=m-O7dS2tYsg

I don't see where he has sonoluminesence. Generally you must dark
accustom your eyes because it is a weak light. and it is light blue in
color maybe moving towards green, but mostly blue as I recall, it's been
20 years.

I agree, maybe he just sees the bubbles forming by shining a light through the vessel.
In sonoluminescence AFAIK the bubbles implode and cause a flash of light.

Not sure his bubbles really implode, but at least he has bubbles.
There was a whole lot to do about those collapsing bubbles causing some radiation.
I have plenty of measurement stuff around for that.
But I think that experiment was refuted as radiation came from some other source in their lab.

I stopped following the endless postings about that (in sci.physics ?) long ago.
Click to expand...

Obviously the collapsing bubble radiates light, so you must be
bringing up some radiation I'm unaware of. I read the wiki, they get
into it, but, didn't understand it.
https://en.wikipedia.org/wiki/Sonoluminescence
Click to expand...


When I saw it it was from our 2" transducer, and a 2" beam of
light zigzaged from aquarium end to aquarium end.
Also with high frequency (40kHz vs 660kHz) you can get about ten times
more power into the water solution before cavitation starts. And bubble
size starts out 1/66 as big for high frequency.
Just regurgitating as I remember things, sorry.

OK.

Main reason I am not trying is I need my ears, and I could imagine standing waves forming
in the fluid in my ears,,, destroying nerve cells.
Click to expand...
OK, that is an advantage of using high frequency 660kHz. The 660kHz is
attenuated 71.5 db per meter of air vs 40kkHz is attenuated 1.38 db per
meter of air. These numbers are a bit low because, as quoted from the
webpage, "this value must be added to the usual distance damping of
audible sound after the 1/r law."
I would assume even though 660kHz is not audible it still follows the
1/r law.
http://www.sengpielaudio.com/calculator-air.htm
Click to expand...



And if it ain't 'nuculear' it is not so interesting anyways.
Where does the light (EM radiation) come from?
Non-linear medium frequency conversion? No too much frequency difference I'd think.
The physics is in a way interesting.
Click to expand...

Yep wish would have figured that out in H.S.
Mikek
 
On 7/16/19 11:55 AM, amdx wrote:
On 7/16/2019 1:53 AM, Jan Panteltje wrote:
On a sunny day (Mon, 15 Jul 2019 14:27:32 -0500) it happened amdx
nojunk@knology.net> wrote in <qgik34$230$1@dont-email.me>:

On 7/15/2019 11:51 AM, Jan Panteltje wrote:
On a sunny day (Mon, 15 Jul 2019 10:09:11 -0500) it happened amdx
nojunk@knology.net> wrote in <qgi4un$ui2$1@dont-email.me>:

I dunno what he means by that either.

Not clear about the question, you don't know anti-resonance or you don't
know why run the transducer at anti-resonance?


'anti resonance' could mean?
[1] Using it out of resonance (that is easy).
[2] Or some magical thing? Then it is bull.
It is either in resonance or it is not, as simple as that.



Ya, you have me wondering if I used the wrong term, but it is the low
impedance point on a an impedance curve.
 When I characterized piezos I only looked at the lowest points, but
this curve continues up in frequency, but it shows my point. We used
them at the low impedance point rather that the high impedance point.
https://www.researchgate.net/figure/The-electrical-impedance-curve-of-the-piezoelectric-disc-transducer-used-for-experiments_fig1_324677066
Click to expand...

Right, that's the mechanical resonance (series resonance in a quartz
crystal). Antiresonance is another word for parallel-resonance.

In my ring-down calibrator thread, the toy oscillator has to resonate
away the parallel capacitance to get the oscillator to run very nearly
at the mechanical (series) resonance.

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com
 
On a sunny day (Tue, 16 Jul 2019 10:55:56 -0500) it happened amdx
<nojunk@knology.net> wrote in <qgks2a$l0b$1@dont-email.me>:

On 7/16/2019 1:53 AM, Jan Panteltje wrote:
On a sunny day (Mon, 15 Jul 2019 14:27:32 -0500) it happened amdx
nojunk@knology.net> wrote in <qgik34$230$1@dont-email.me>:

On 7/15/2019 11:51 AM, Jan Panteltje wrote:
On a sunny day (Mon, 15 Jul 2019 10:09:11 -0500) it happened amdx
nojunk@knology.net> wrote in <qgi4un$ui2$1@dont-email.me>:

I dunno what he means by that either.

Not clear about the question, you don't know anti-resonance or you don't
know why run the transducer at anti-resonance?


'anti resonance' could mean?
[1] Using it out of resonance (that is easy).
[2] Or some magical thing? Then it is bull.
It is either in resonance or it is not, as simple as that.



Ya, you have me wondering if I used the wrong term, but it is the low
impedance point on a an impedance curve.
When I characterized piezos I only looked at the lowest points, but
this curve continues up in frequency, but it shows my point. We used
them at the low impedance point rather that the high impedance point.

https://www.researchgate.net/figure/The-electrical-impedance-curve-of-the-piezoelectric-disc-transducer-used-for-experiments_fig1_324677066
Click to expand...

Maybe the term is 'series resonance',
because if you would drive the (normally capacitive) piezo
with a series inductor it would show low impedance at the resonance point

signal generator ->- L ->- transducer ->- ground
L C

So if L and C are driven as above, you drive indeed into a low impedance with a huge current.
For 40 kHz and 3.7 nF according to
https://www.daycounter.com/Calculators/LC-Resonance-Calculator.phtml
L would have to be 4.28e+6 is 4.28 uH, a small coil realy.
if I did not make a typo.

It is a few thousand pF for my transducers IIRC, would have to look it up.
My design was based on this idea
http://archive.siliconchip.com.au/cms/A_112107/article.html
but I used a 'little bit' more power and some extra software.


The sonoluninescence can also be done with the transducers I have,
there is even a youtube video from somebody who did just that:
https://www.youtube.com/watch?v=m-O7dS2tYsg

I don't see where he has sonoluminesence. Generally you must dark
accustom your eyes because it is a weak light. and it is light blue in
color maybe moving towards green, but mostly blue as I recall, it's been
20 years.

I agree, maybe he just sees the bubbles forming by shining a light through the vessel.
In sonoluminescence AFAIK the bubbles implode and cause a flash of light.

Not sure his bubbles really implode, but at least he has bubbles.
There was a whole lot to do about those collapsing bubbles causing some radiation.
I have plenty of measurement stuff around for that.
But I think that experiment was refuted as radiation came from some other source in their lab.

I stopped following the endless postings about that (in sci.physics ?) long ago.

Obviously the collapsing bubble radiates light, so you must be
bringing up some radiation I'm unaware of. I read the wiki, they get
into it, but, didn't understand it.
https://en.wikipedia.org/wiki/Sonoluminescence
Click to expand...

<quote>
On January 27, 2006, researchers at Rensselaer Polytechnic Institute claimed to have produced fusion in sonoluminescence experiments.
Experiments in 2002 and 2005 by R. P. Taleyarkhan using deuterated acetone showed measurements of tritium and neutron output consistent with fusion.
However, the papers were considered low quality and there were doubts
cast by a report about the author's scientific misconduct. This made the report lose credibility among the scientific community.
<end quote>

So whatever, IF I ever do the experiment I will put my gamma spectrometer next to it for sure...
Cold fusion, and this, a lot was discussed in those years on the internet.
I am sceptical by nature,...

Actually that series resonance mode I will have to try that!
Because that would be easy with any high end audio power amp at 40 kHz and you do not need a transformer!
Now on the todo list (with a thousand other things).

How the collapsing bubble gives light? Squeeze anything hard enough and it will heat up.
Some gases may light up at high temperature,
That is the gist I get from your wikipedia link.


When I saw it it was from our 2" transducer, and a 2" beam of
light zigzaged from aquarium end to aquarium end.
Also with high frequency (40kHz vs 660kHz) you can get about ten times
more power into the water solution before cavitation starts. And bubble
size starts out 1/66 as big for high frequency.
Just regurgitating as I remember things, sorry.

OK.

Main reason I am not trying is I need my ears, and I could imagine standing waves forming
in the fluid in my ears,,, destroying nerve cells.

OK, that is an advantage of using high frequency 660kHz. The 660kHz is
attenuated 71.5 db per meter of air vs 40kHz is attenuated 1.38 db per
meter of air. These numbers are a bit low because, as quoted from the
webpage, "this value must be added to the usual distance damping of
audible sound after the 1/r law."
I would assume even though 660kHz is not audible it still follows the
1/r law.
http://www.sengpielaudio.com/calculator-air.htm
Click to expand...

Cool calculator, did not know that, thanks!
 
On 7/16/2019 7:46 AM, George Herold wrote:
On Monday, July 15, 2019 at 10:23:56 PM UTC-4, amdx wrote:
On 7/15/2019 2:49 PM, George Herold wrote:
On Monday, July 15, 2019 at 2:17:27 AM UTC-4, Jan Panteltje wrote:
On a sunny day (Sun, 14 Jul 2019 15:48:20 -0500) it happened amdx
nojunk@knology.net> wrote in <qgg4eo$14i$1@dont-email.me>:

On 7/14/2019 1:13 PM, Jan Panteltje wrote:
On a sunny day (14 Jul 2019 10:37:47 -0700) it happened Winfield Hill
winfieldhill@yahoo.com> wrote in <qgfp9b0f1s@drn.newsguy.com>:

I'm finishing a section on charge-based piezo
drive. Anybody want to say anything about it?

What is a 'charge based' piezo drive?

I am driving some big 40 kHz piezos hard with a MOSFET push pull circuit
and transformer, PIC as signal generator.
These:
https://www.ebay.com/itm/400728340024
2 pieces, 120W total, from 12V DC.


When I worked at a small company called Ultrasonic Energy Systems.
We drove a 2" round x 0.80" thick PZT8 ceramic bonded to a 1/16"
aluminum plate at 1000 watts pulsed and 250 continuous.
We also had it in an ice water bath. to keep the transducer cool.
We ran the transducers around 660kHz, whereever the maximum efficiency
was. We treated solution in a vessel through an FEP Teflon 0.003" window.
One of our customers substituted PTFE for the FEP window and could not
repeat results. He has killing bacteria in milk, after the teflon sub,
his kill rate went way down.
FUN fact; we could watch sonoluminescence go across a 20" aquarium,
reflect off the glass go to the other end and reflect
again before dying off.
First design was a class A amplifier, second one we used class E.
The class E driver design was stupid, we had an osc and a couple of
tuned preamps, to drive four Mosfets. By then there were good mosfet
drivers, the tuned circuits were a PITA, I was the one winding coils and
transformers.
Probably OK for a physicist designing electronics. (Not me)
Our claim to fame was the sale of a 4000 watt unit to Cal Tech,
it used 4- 4" x 4" ceramics, with about a 1 gallon flow through
treatment vessel.
I remember those years fondly.
Mikek


I always wanted to do that sonoluminescence experiment,
but am a bit afraid of all that high power 40 kHz for my ears.
Jan, one hint about sonoluminescence. The water has to have to air taken
out of it. We did this by boiling the water, then cooling it (with cap on)
And then you've got an hour or so till the air diffuses back in.
PITA of an experiment, and not really worth much over the 'Gee- Whiz'
factor.

George H.

Hi George,
I will have to disagree with you about degassing the water.
We didn't degassed our water and didn't have any problem getting
sonoluminescence. Only differing factor is, we used high frequency,
but I don't think that matters.
In some experiments we added air, (sparge gas) to enhance reactions.
In the link below is a writeup about sparge gases by my boss, Henry.
In it he starts with Ultrasound removal of Carbon Dioxide from water,
but the interesting part is at about 1/3 of they way down where it says,
FEATURED ARTICLE. It talks about using Noble gases as the sparge gas
having increased enhancement of reactions over air.

https://web.archive.org/web/20060216195024/http://www.ultrasonic-energy.com/shop_talk.html

I have more, but I get tired, maybe tomorrow.
OK thanks Mike. Perhaps the unit we had was under-powered and didn't have
enough to make flashes w/o removing the air.

George H.

Mikek
Click to expand...

OK here's what I was working on when I quit last night.
This is a graph from,
Sonochemistry:
Theory, Applications and Uses of Ultrasound in Chemistry.

The chart is labeled,
"Bubble Formation and the Factors affecting cavitation Threshold"
It plots intensity over frequency for aerated and degassed water,
and shows the cavitation threshold.
I added the lines for 40kHz and 660kHz and the power levels where they
cross, I also added the power values. Please feel free to check my lines
and values. I had to extrapolate in my own way.

Now, as to what it means.
Don't know if these are positives or negatives, probably depends on
what you are doing.
You get much higher sonic power into solution before cavitation.
You can get much higher sonic power into solution before cavitation on
your faceplate causes it's problems. (faceplate erosion, cavitation in
front of faceplate blocks sound transmission and alters transducer
impedance)
So, without further ado,
> https://www.dropbox.com/s/07dgqxafqbm4f8x/Cavitation%20paint.jpg?dl=0

Mikek




The PIC I programmed for this does at start up do a range of frequency increments,
At the same time it measures output voltage for each frequency and remembers the best one
representing resonance.
It then uses that one, takes about a 2 seconds run to find it.
It can do an automatic range of other pings too, is for anti-fauling in boats.

I still have no idea what a 'charge based' piezo drive is?
It is all about resonance AFAIK.

What I find amazing is those little beepers, I have one from China, that make a +120 dB 3 KHz or so beep
hardly using any power, have one as alarm here, you cannot live in that noise.. few mW?
Click to expand...
 
On a sunny day (Tue, 16 Jul 2019 13:26:49 -0500) it happened amdx
<nojunk@knology.net> wrote in <qgl4te$ehr$1@dont-email.me>:

The chart is labeled,
"Bubble Formation and the Factors affecting cavitation Threshold"
It plots intensity over frequency for aerated and degassed water,
and shows the cavitation threshold.
I added the lines for 40kHz and 660kHz and the power levels where they
cross, I also added the power values. Please feel free to check my lines
and values. I had to extrapolate in my own way.
Now, as to what it means.
Don't know if these are positives or negatives, probably depends on
what you are doing.
You get much higher sonic power into solution before cavitation.
You can get much higher sonic power into solution before cavitation on
your faceplate causes it's problems. (faceplate erosion, cavitation in
front of faceplate blocks sound transmission and alters transducer
impedance)
So, without further ado,
https://www.dropbox.com/s/07dgqxafqbm4f8x/Cavitation%20paint.jpg?dl=0

Mikek
Click to expand...

So to make the bubbles requires much less power at 40 kHz,
that is why the youtube guy has all the bubbles with a simple signal source I think.
I should not have any problems with my transducers and even
less if I use a 75 W RMS audio amp and series resonance ??
Thanks for the chart.
 
On 2019/07/14 11:44 a.m., Chris wrote:
On Sun, 14 Jul 2019 10:37:47 -0700, Winfield Hill wrote:

I'm finishing a section on charge-based piezo drive. Anybody want to
say anything about it?

Is that some sort of threat?
Click to expand...

Slide rules @ noon @ the Piezo Corral!

John ;-#)#
 
On 7/16/2019 1:44 PM, Jan Panteltje wrote:
On a sunny day (Tue, 16 Jul 2019 13:26:49 -0500) it happened amdx
nojunk@knology.net> wrote in <qgl4te$ehr$1@dont-email.me>:

The chart is labeled,
"Bubble Formation and the Factors affecting cavitation Threshold"
It plots intensity over frequency for aerated and degassed water,
and shows the cavitation threshold.
I added the lines for 40kHz and 660kHz and the power levels where they
cross, I also added the power values. Please feel free to check my lines
and values. I had to extrapolate in my own way.
Now, as to what it means.
Don't know if these are positives or negatives, probably depends on
what you are doing.
You get much higher sonic power into solution before cavitation.
You can get much higher sonic power into solution before cavitation on
your faceplate causes it's problems. (faceplate erosion, cavitation in
front of faceplate blocks sound transmission and alters transducer
impedance)
So, without further ado,
https://www.dropbox.com/s/07dgqxafqbm4f8x/Cavitation%20paint.jpg?dl=0

Mikek

So to make the bubbles requires much less power at 40 kHz,
that is why the youtube guy has all the bubbles with a simple signal source I think.
I should not have any problems with my transducers and even
less if I use a 75 W RMS audio amp and series resonance ??
Thanks for the chart.
Click to expand...
Yes, :)
But for chemistry you want higher frequency, many more bubbles, more
cavitation points, much more surface area.
Can anyone tell me about about Dispersion angle? Is the angle
different for a 40kHz transducer vs a 660kHz transducer?
I wonder, we pointed our 2" transducer at a convexed 4" air backed
reflector, it caused a focus of energy about 2" in front of the
reflector. At that point you had a approx 3/4" cottony froth and a
hissing from the intense cavitation at the focus.
I wonder if 40kHz would disperse, or would all the energy reflect from
the convexed reflector. About 8" away, although in some experiments we
where up to 15" away.


Here's a good video showing single bubble sonoluminesense.
https://www.youtube.com/watch?v=YJ3G3obIBWQ
Click to expand...

Here's a video, but I am skeptical, things just don't seem right. See
my comment below the video.
https://www.youtube.com/watch?v=YJ3G3obIBWQ
Mikek
Click to expand...
 
On 17/7/19 3:19 am, Jan Panteltje wrote:
Actually that series resonance mode I will have to try that!
Because that would be easy with any high end audio power amp at 40 kHz and you do not need a transformer!
Now on the todo list (with a thousand other things).

How the collapsing bubble gives light? Squeeze anything hard enough and it will heat up.
Some gases may light up at high temperature,
That is the gist I get from your wikipedia link.
Click to expand...
Because it's not a bubble. It's a vacuum cavity, so there's nothing to
buffer the shock of opposite faces impacting when the cavity closes. Any
water vapor re-absorbs instantly, and water is so incompressible that
there are huge local pressure spikes. This is what causes surface
erosion on drag boat propellors.
 
onsdag den 17. juli 2019 kl. 01.02.01 UTC+2 skrev Clifford Heath:
On 17/7/19 3:19 am, Jan Panteltje wrote:
Actually that series resonance mode I will have to try that!
Because that would be easy with any high end audio power amp at 40 kHz and you do not need a transformer!
Now on the todo list (with a thousand other things).

How the collapsing bubble gives light? Squeeze anything hard enough and it will heat up.
Some gases may light up at high temperature,
That is the gist I get from your wikipedia link.
Because it's not a bubble. It's a vacuum cavity, so there's nothing to
buffer the shock of opposite faces impacting when the cavity closes. Any
water vapor re-absorbs instantly, and water is so incompressible that
there are huge local pressure spikes. This is what causes surface
erosion on drag boat propellors.
Click to expand...

this is from a pump, https://i.imgur.com/5sKNddK.jpg
 
On 7/16/2019 6:32 PM, Lasse Langwadt Christensen wrote:
onsdag den 17. juli 2019 kl. 01.02.01 UTC+2 skrev Clifford Heath:
On 17/7/19 3:19 am, Jan Panteltje wrote:
Actually that series resonance mode I will have to try that!
Because that would be easy with any high end audio power amp at 40 kHz and you do not need a transformer!
Now on the todo list (with a thousand other things).

How the collapsing bubble gives light? Squeeze anything hard enough and it will heat up.
Some gases may light up at high temperature,
That is the gist I get from your wikipedia link.
Because it's not a bubble. It's a vacuum cavity, so there's nothing to
buffer the shock of opposite faces impacting when the cavity closes. Any
water vapor re-absorbs instantly, and water is so incompressible that
there are huge local pressure spikes. This is what causes surface
erosion on drag boat propellors.

this is from a pump, https://i.imgur.com/5sKNddK.jpg
Click to expand...

Just read an article about steel printing press rollers, they went
from chemical cleaning to ultrasonic cleaning all of the sudden they find
the rollers would "carry more ink more efficiently and uniformly."
The writer speculated two possibilities,
The implosions of cavitation bubbles may have created small
“craters” in the surface which improved the “tooth” of the surface.
or
The surface had been “machined” sufficiently to remove a thin skin
of oxide or other barrier which otherwise prevented adhesion of ink.

Mikek
 
On 7/16/2019 6:32 PM, Lasse Langwadt Christensen wrote:
onsdag den 17. juli 2019 kl. 01.02.01 UTC+2 skrev Clifford Heath:
On 17/7/19 3:19 am, Jan Panteltje wrote:
Actually that series resonance mode I will have to try that!
Because that would be easy with any high end audio power amp at 40 kHz and you do not need a transformer!
Now on the todo list (with a thousand other things).

How the collapsing bubble gives light? Squeeze anything hard enough and it will heat up.
Some gases may light up at high temperature,
That is the gist I get from your wikipedia link.
Because it's not a bubble. It's a vacuum cavity, so there's nothing to
buffer the shock of opposite faces impacting when the cavity closes. Any
water vapor re-absorbs instantly, and water is so incompressible that
there are huge local pressure spikes. This is what causes surface
erosion on drag boat propellors.

this is from a pump, https://i.imgur.com/5sKNddK.jpg
Click to expand...

Slow motion cavitation bubble collapse.
> https://techblog.ctgclean.com/2019/03/cavitation-bubble-implosion-video/

Mikek
 
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