https://www.dropbox.com/scl/fi/a7425c69k3w8wx8tqjpq5/X110_CV_Test.jpg?rlkey=pc3c0b12ncswv6ajrn148stdk&raw=1
The DUT is a Venkel 2.2 uF 100v 1812-size ceramic cap. I need to run
it at 48 volts. 0.8 uF is probably OK. I have room on my board so I
guess I'll add another cap in parallel.
My AADE cap meter was behaving strangely here, so I measured C by
noting the -3 dB frequency driving the cap from a 50 ohm sine wave
generator.
On 5/1/25 22:09, john larkin wrote:
https://www.dropbox.com/scl/fi/a7425c69k3w8wx8tqjpq5/X110_CV_Test.jpg?rlkey=pc3c0b12ncswv6ajrn148stdk&raw=1
The DUT is a Venkel 2.2 uF 100v 1812-size ceramic cap. I need to run
it at 48 volts. 0.8 uF is probably OK. I have room on my board so I
guess I'll add another cap in parallel.
My AADE cap meter was behaving strangely here, so I measured C by
noting the -3 dB frequency driving the cap from a 50 ohm sine wave
generator.
I used an old Rohde & Schwarz KARU capacitance meter to match
capacitors. It was really good at that, but sometimes it just
wouldn't work. At some point, I decided to finally figure out
why. It turned out the KARU applied over 300Vpp of AC at tens
of kHz to my little capacitors.
Oh.
Jeroen Belleman
https://www.dropbox.com/scl/fi/a7425c69k3w8wx8tqjpq5/X110_CV_Test.jpg?rlkey=pc3c0b12ncswv6ajrn148stdk&raw=1
The DUT is a Venkel 2.2 uF 100v 1812-size ceramic cap. I need to run
it at 48 volts. 0.8 uF is probably OK. I have room on my board so I
guess I'll add another cap in parallel.
On 5/1/25 22:09, john larkin wrote:
https://www.dropbox.com/scl/fi/a7425c69k3w8wx8tqjpq5/X110_CV_Test.jpg?rlkey=pc3c0b12ncswv6ajrn148stdk&raw=1
The DUT is a Venkel 2.2 uF 100v 1812-size ceramic cap. I need to run
it at 48 volts. 0.8 uF is probably OK. I have room on my board so I
guess I'll add another cap in parallel.
or in series, I believe there are some automotive standards that call
for that on high current lines because ceramics tend to fail short with >mechanical stress
Two of those caps in series would make about half the capacitance of
two in parallel, but ESR and ESL would suffer by 4:1.
On 2025-05-04, john larkin <jl@glen--canyon.com> wrote:
Two of those caps in series would make about half the capacitance of
two in parallel, but ESR and ESL would suffer by 4:1.
Not really - according to your measurements, at 25V, the caps should have >about 1.46uF, so the series combination has 0.73uF instead of the 0.83uF of >the parallel combination.
cu
Michael
On 04/05/2025 03:17, john larkin wrote:
On Sun, 4 May 2025 02:11:47 +0200, Lasse Langwadt <llc@fonz.dk> wrote:
On 5/1/25 22:09, john larkin wrote:
https://www.dropbox.com/scl/fi/a7425c69k3w8wx8tqjpq5/X110_CV_Test.jpg?rlkey=pc3c0b12ncswv6ajrn148stdk&raw=1
The DUT is a Venkel 2.2 uF 100v 1812-size ceramic cap. I need to run
it at 48 volts. 0.8 uF is probably OK. I have room on my board so I
guess I'll add another cap in parallel.
or in series, I believe there are some automotive standards that call
for that on high current lines because ceramics tend to fail short with
mechanical stress
Two of those caps in series would make about half the capacitance of
two in parallel, but ESR and ESL would suffer by 4:1.
We don't see many ceramic cap failures. Our worst parts are "sealed"
relays that actually aren't. Some switches, too.
We don't use surface-mount film caps. They are awful.
Even the PPS type?
John
Not really - according to your measurements, at 25V, the caps should have >>about 1.46uF, so the series combination has 0.73uF instead of the 0.83uF of >>the parallel combination.
One cap is .83 at 50 volts. Two in parallel would be 1.66.
The series pair is about .73 as you note. That assumes that the DC
voltage divides equally.
Ceramic cap nonlinearity is weird. To get the most C, is it always
better to pick the cap with the highest nameplate capacitance?
On 4 May 2025 11:17:07 GMT, Michael Schwingen ><news-1513678000@discworld.dascon.de> wrote:
On 2025-05-04, john larkin <jl@glen--canyon.com> wrote:
Two of those caps in series would make about half the capacitance of
two in parallel, but ESR and ESL would suffer by 4:1.
Not really - according to your measurements, at 25V, the caps should have >>about 1.46uF, so the series combination has 0.73uF instead of the 0.83uF of >>the parallel combination.
cu
Michael
One cap is .83 at 50 volts. Two in parallel would be 1.66.
The series pair is about .73 as you note. That assumes that the DC
voltage divides equally.
Ceramic cap nonlinearity is weird. To get the most C, is it always
better to pick the cap with the highest nameplate capacitance?
Some caps are 1/5 their rated C at their rated voltage. Bad for timing >circuits.
On 2025-05-04, john larkin <jl@glen--canyon.com> wrote:
Not really - according to your measurements, at 25V, the caps should have >>>about 1.46uF, so the series combination has 0.73uF instead of the 0.83uF of >>>the parallel combination.
One cap is .83 at 50 volts. Two in parallel would be 1.66.
The series pair is about .73 as you note. That assumes that the DC
voltage divides equally.
Upps, yes. Must have been lack of coffee.
Ceramic cap nonlinearity is weird. To get the most C, is it always
better to pick the cap with the highest nameplate capacitance?
Not sure. In one case where I needed about 9uF at 12V DC, standard X5R/X7R >22uF/25V all came out at about 7.5uF, and 22uF/35V were not a bit better.
IIRC, X7S performed much better.
Murata Simsurfing has typical Capacitance/DC bias curves for all their parts.
cu
Michael
On Sun, 04 May 2025 07:27:55 -0700, john larkin <jl@glen--canyon.com>
wrote:
On 4 May 2025 11:17:07 GMT, Michael Schwingen >><news-1513678000@discworld.dascon.de> wrote:
On 2025-05-04, john larkin <jl@glen--canyon.com> wrote:
Two of those caps in series would make about half the capacitance of
two in parallel, but ESR and ESL would suffer by 4:1.
Not really - according to your measurements, at 25V, the caps should have >>>about 1.46uF, so the series combination has 0.73uF instead of the 0.83uF of >>>the parallel combination.
cu
Michael
One cap is .83 at 50 volts. Two in parallel would be 1.66.
The series pair is about .73 as you note. That assumes that the DC
voltage divides equally.
Ceramic cap nonlinearity is weird. To get the most C, is it always
better to pick the cap with the highest nameplate capacitance?
Some caps are 1/5 their rated C at their rated voltage. Bad for timing >>circuits.
Essential to test 'em then! Are you really getting SRFs as low as just
a few K?
On Sun, 04 May 2025 18:31:20 +0100, Cursitor Doom <cd@notformail.com>
wrote:
On Sun, 04 May 2025 07:27:55 -0700, john larkin <jl@glen--canyon.com> >>wrote:
On 4 May 2025 11:17:07 GMT, Michael Schwingen >>><news-1513678000@discworld.dascon.de> wrote:
On 2025-05-04, john larkin <jl@glen--canyon.com> wrote:
Two of those caps in series would make about half the capacitance of >>>>> two in parallel, but ESR and ESL would suffer by 4:1.
Not really - according to your measurements, at 25V, the caps should have >>>>about 1.46uF, so the series combination has 0.73uF instead of the 0.83uF of >>>>the parallel combination.
cu
Michael
One cap is .83 at 50 volts. Two in parallel would be 1.66.
The series pair is about .73 as you note. That assumes that the DC >>>voltage divides equally.
Ceramic cap nonlinearity is weird. To get the most C, is it always
better to pick the cap with the highest nameplate capacitance?
Some caps are 1/5 their rated C at their rated voltage. Bad for timing >>>circuits.
Essential to test 'em then! Are you really getting SRFs as low as just
a few K?
I wasn't measuring SRF. I eyeballed the -3 dB point where the cap
impedance was 50 ohms.
Maybe 1 nH and 2.2 uF would have its SRF null around 3 MHz.
On Sun, 04 May 2025 12:07:28 -0700, john larkin <jl@glen--canyon.com>
wrote:
On Sun, 04 May 2025 18:31:20 +0100, Cursitor Doom <cd@notformail.com> >>wrote:
On Sun, 04 May 2025 07:27:55 -0700, john larkin <jl@glen--canyon.com> >>>wrote:
On 4 May 2025 11:17:07 GMT, Michael Schwingen >>>><news-1513678000@discworld.dascon.de> wrote:
On 2025-05-04, john larkin <jl@glen--canyon.com> wrote:
Two of those caps in series would make about half the capacitance of >>>>>> two in parallel, but ESR and ESL would suffer by 4:1.
Not really - according to your measurements, at 25V, the caps should have >>>>>about 1.46uF, so the series combination has 0.73uF instead of the 0.83uF of
the parallel combination.
cu
Michael
One cap is .83 at 50 volts. Two in parallel would be 1.66.
The series pair is about .73 as you note. That assumes that the DC >>>>voltage divides equally.
Ceramic cap nonlinearity is weird. To get the most C, is it always >>>>better to pick the cap with the highest nameplate capacitance?
Some caps are 1/5 their rated C at their rated voltage. Bad for timing >>>>circuits.
Essential to test 'em then! Are you really getting SRFs as low as just
a few K?
I wasn't measuring SRF. I eyeballed the -3 dB point where the cap
impedance was 50 ohms.
Maybe 1 nH and 2.2 uF would have its SRF null around 3 MHz.
So what's the "Fo" in your diagram refer to?
john larkin wrote:
https://www.dropbox.com/scl/fi/a7425c69k3w8wx8tqjpq5/X110_CV_Test.jpg?rlkey=pc3c0b12ncswv6ajrn148stdk&raw=1
The DUT is a Venkel 2.2 uF 100v 1812-size ceramic cap. I need to run
it at 48 volts. 0.8 uF is probably OK. I have room on my board so I
guess I'll add another cap in parallel.
My AADE cap meter was behaving strangely here, so I measured C by
noting the -3 dB frequency driving the cap from a 50 ohm sine wave
generator.
Do inductors vary with current as well? I would guess only a little bit.
john larkin wrote:
https://www.dropbox.com/scl/fi/a7425c69k3w8wx8tqjpq5/X110_CV_Test.jpg?rlkey=pc3c0b12ncswv6ajrn148stdk&raw=1
The DUT is a Venkel 2.2 uF 100v 1812-size ceramic cap. I need to run
it at 48 volts. 0.8 uF is probably OK. I have room on my board so I
guess I'll add another cap in parallel.
My AADE cap meter was behaving strangely here, so I measured C by
noting the -3 dB frequency driving the cap from a 50 ohm sine wave
generator.
Do inductors vary with current as well? I would guess only a little bit.
On 5/05/2025 9:20 pm, Tom Del Rosso wrote:
john larkin wrote:
https://www.dropbox.com/scl/fi/a7425c69k3w8wx8tqjpq5/X110_CV_Test.jpg?rlkey=pc3c0b12ncswv6ajrn148stdk&raw=1
The DUT is a Venkel 2.2 uF 100v 1812-size ceramic cap. I need to run
it at 48 volts. 0.8 uF is probably OK. I have room on my board so I
guess I'll add another cap in parallel.
My AADE cap meter was behaving strangely here, so I measured C by
noting the -3 dB frequency driving the cap from a 50 ohm sine wave
generator.
Do inductors vary with current as well? I would guess only a little
bit.
Yes.
http://www.vk2zay.net/article/200
https://www.dropbox.com/scl/fi/a7425c69k3w8wx8tqjpq5/X110_CV_Test.jpg?rlkey=pc3c0b12ncswv6ajrn148stdk&raw=1
The DUT is a Venkel 2.2 uF 100v 1812-size ceramic cap. I need to run
it at 48 volts. 0.8 uF is probably OK. I have room on my board so I
guess I'll add another cap in parallel.
My AADE cap meter was behaving strangely here, so I measured C by
noting the -3 dB frequency driving the cap from a 50 ohm sine wave
generator.
Chris Jones wrote:
On 5/05/2025 9:20 pm, Tom Del Rosso wrote:
john larkin wrote:
https://www.dropbox.com/scl/fi/a7425c69k3w8wx8tqjpq5/X110_CV_Test.jpg?rlkey=pc3c0b12ncswv6ajrn148stdk&raw=1
The DUT is a Venkel 2.2 uF 100v 1812-size ceramic cap. I need to run
it at 48 volts. 0.8 uF is probably OK. I have room on my board so I
guess I'll add another cap in parallel.
My AADE cap meter was behaving strangely here, so I measured C by
noting the -3 dB frequency driving the cap from a 50 ohm sine wave
generator.
Do inductors vary with current as well? I would guess only a little
bit.
Yes.
http://www.vk2zay.net/article/200
With saturation, yes, but what about the usable range?
https://www.dropbox.com/scl/fi/a7425c69k3w8wx8tqjpq5/X110_CV_Test.jpg?rlkey=pc3c0b12ncswv6ajrn148stdk&raw=1
The DUT is a Venkel 2.2 uF 100v 1812-size ceramic cap. I need to run
it at 48 volts. 0.8 uF is probably OK. I have room on my board so I
guess I'll add another cap in parallel.
My AADE cap meter was behaving strangely here, so I measured C by
noting the -3 dB frequency driving the cap from a 50 ohm sine wave
generator.
| Sysop: | Keyop |
|---|---|
| Location: | Huddersfield, West Yorkshire, UK |
| Users: | 489 |
| Nodes: | 16 (2 / 14) |
| Uptime: | 46:16:14 |
| Calls: | 9,670 |
| Calls today: | 1 |
| Files: | 13,719 |
| Messages: | 6,170,073 |
