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Groups > sci.electronics.design > #446400 > unrolled thread
| Started by | Prof78 <scott.hamilton@manchester.ac.uk> |
|---|---|
| First post | 2017-02-06 05:31 -0800 |
| Last post | 2017-02-08 17:56 -0600 |
| Articles | 8 on this page of 28 — 13 participants |
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Capacitor soakage Prof78 <scott.hamilton@manchester.ac.uk> - 2017-02-06 05:31 -0800
Re: Capacitor soakage Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> - 2017-02-06 08:57 -0500
Re: Capacitor soakage Prof78 <scott.hamilton@manchester.ac.uk> - 2017-02-08 08:43 -0800
Re: Capacitor soakage Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-02-08 11:59 -0500
Re: Capacitor soakage George Herold <gherold@teachspin.com> - 2017-02-08 10:30 -0800
Re: Capacitor soakage Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-02-08 13:39 -0500
Re: Capacitor soakage John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-02-08 12:38 -0800
Re: Capacitor soakage Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-02-08 16:11 -0500
Re: Capacitor soakage John Larkin <jjlarkin@highlandtechnology.com> - 2017-02-09 08:30 -0800
Re: Capacitor soakage Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2017-02-09 14:55 -0500
Re: Capacitor soakage bill.sloman@ieee.org - 2017-02-08 14:53 -0800
Re: Capacitor soakage Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> - 2017-02-08 19:11 -0500
Re: Capacitor soakage Frank Miles <fpm@u.washington.edu> - 2017-02-08 22:36 +0000
Re: Capacitor soakage George Herold <gherold@teachspin.com> - 2017-02-08 17:48 -0800
Re: Capacitor soakage John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-02-09 11:17 -0800
Re: Capacitor soakage "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-02-09 16:46 -0600
Re: Capacitor soakage krw@notreal.com - 2017-02-09 20:44 -0500
Re: Capacitor soakage bill.sloman@ieee.org - 2017-02-09 19:15 -0800
Re: Capacitor soakage John Larkin <jjlarkin@highlandtechnology.com> - 2017-02-09 20:54 -0800
Re: Capacitor soakage John Larkin <jjlarkinxyxy@highlandtechnology.com> - 2017-02-09 11:16 -0800
Re: Capacitor soakage George Herold <gherold@teachspin.com> - 2017-02-09 12:02 -0800
Re: Capacitor soakage Robert Baer <robertbaer@localnet.com> - 2017-02-08 20:50 -0800
Re: Capacitor soakage George Herold <gherold@teachspin.com> - 2017-02-09 06:36 -0800
Re: Capacitor soakage Phil Allison <pallison49@gmail.com> - 2017-02-08 17:10 -0800
Re: Capacitor soakage Phil Allison <pallison49@gmail.com> - 2017-02-06 06:51 -0800
Re: Capacitor soakage Prof78 <scott.hamilton@manchester.ac.uk> - 2017-02-08 08:32 -0800
Re: Capacitor soakage Tim Wescott <seemywebsite@myfooter.really> - 2017-02-08 17:48 -0600
Re: Capacitor soakage "Tim Williams" <tiwill@seventransistorlabs.com> - 2017-02-08 17:56 -0600
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| From | George Herold <gherold@teachspin.com> |
|---|---|
| Date | 2017-02-09 12:02 -0800 |
| Message-ID | <ecda3fd6-4195-4483-bc1c-305ab96e6191@googlegroups.com> |
| In reply to | #447044 |
On Thursday, February 9, 2017 at 2:16:15 PM UTC-5, John Larkin wrote: > On Wed, 8 Feb 2017 22:36:32 -0000 (UTC), Frank Miles > <fpm@u.washington.edu> wrote: > > >On Wed, 08 Feb 2017 10:30:28 -0800, George Herold wrote: > > > >> On Wednesday, February 8, 2017 at 11:59:10 AM UTC-5, Phil Hobbs wrote: > >>> On 02/08/2017 11:43 AM, Prof78 wrote: > >>> > On Monday, 6 February 2017 13:57:52 UTC, Spehro Pefhany wrote: > >>> >> On Mon, 6 Feb 2017 05:31:04 -0800 (PST), the renowned Prof78 > >>> >> <scott.hamilton@manchester.ac.uk> wrote: > >>> >> > >>> >>> Looking for advice/experience on measurement of capacitor > >>> >>> soakage. Would like to determine an approximate equivalent > >>> >>> circuit for a 1uF polypropylene capacitor at very low > >>> >>> frequency/time intervals of tens of seconds. > >>> >>> > >>> >>> Scott Hamilton. > >>> >> > >>> >> > >>> >> Did you read Bob Pease's article? A bunch of RC's in parallel with > >>> >> an ideal cap should do it. > >>> >> > >>> >> --sp > >>> >> > >>> >> > >>> >> -- Best regards, Spehro Pefhany > >>> > > >>> > Yes I have read the articles by Bob Pease but I need to be able to > >>> > measure and determine the equivalent circuit for a given capacitor so > >>> > that compensation can be applied. Each unit is hand adjusted. > >>> > >>> Yikes, that sounds like nailing jello to a tree. Do you have any reason > >>> to suppose that all the internal time constants would be > >>> temperature-independent? Cuz otherwise that's a nasty calibration table > >>> to create. > >> > >> Is there any reason to believe it will be linear with the voltage step? > >> (Sounds like a research project.) > >> > >> I thought I read once that teflon caps had low soakage. Maybe they > >> are better than polypropylene? > >> > >> George h. > >>> > >>> Cheers > >>> > >>> Phil Hobbs > >>> > >>> -- > >>> Dr Philip C D Hobbs > >>> Principal Consultant > >>> ElectroOptical Innovations LLC > >>> Optics, Electro-optics, Photonics, Analog Electronics > >>> > >>> 160 North State Road #203 > >>> Briarcliff Manor NY 10510 > >>> > >>> hobbs at electrooptical dot net > >>> http://electrooptical.net > > > >My dim recollection is that teflon is not so good. It wouldn't be surprising - > >fluorine having such strong electronegativity would likely have a "polarizing" > >effect that could be subject to relaxation responses. > > Teflon is great for dielectric absorption and insulation, but its > temperature coefficient is ghastly. It goes through a phase change > right around room temp. > > It's hard to find teflon caps above about 50 pF. I found this yesterday, but couldn't really see any prices or specs... http://www.exxelia.com/all-products/capacitors/films/high-temperature-film-capacitors/ It looks bigger than 50 pF :^) George h. > > > > >Mylar is definitely bad; polycarbonates not great either. Polypropylene is > >good, perhaps nearly as good as the ever-meltable polystyrene. > > The second ADC that I designed was a dual-slope, and in ignorance I > used a mylar cap as the integrator. It was terrible, several per cent > error. A tech fixed it for me. > > > > >The ceramics are mostly mediocre (or worse), though some of the newer C0Gs are > >close to polypropylene. > > > C0Gs are usually good. SiO2 (MIS) caps are superb, but are usually > found inside chips. There are some for sale as discretes. > > > -- > > John Larkin Highland Technology, Inc > picosecond timing precision measurement > > jlarkin att highlandtechnology dott com > http://www.highlandtechnology.com
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| From | Robert Baer <robertbaer@localnet.com> |
|---|---|
| Date | 2017-02-08 20:50 -0800 |
| Message-ID | <NySmA.33236$VV2.5342@fx33.iad> |
| In reply to | #446827 |
George Herold wrote: > On Wednesday, February 8, 2017 at 11:59:10 AM UTC-5, Phil Hobbs wrote: >> On 02/08/2017 11:43 AM, Prof78 wrote: >>> On Monday, 6 February 2017 13:57:52 UTC, Spehro Pefhany wrote: >>>> On Mon, 6 Feb 2017 05:31:04 -0800 (PST), the renowned Prof78 >>>> <scott.hamilton@manchester.ac.uk> wrote: >>>> >>>>> Looking for advice/experience on measurement of capacitor >>>>> soakage. Would like to determine an approximate equivalent >>>>> circuit for a 1uF polypropylene capacitor at very low >>>>> frequency/time intervals of tens of seconds. >>>>> >>>>> Scott Hamilton. >>>> >>>> >>>> Did you read Bob Pease's article? A bunch of RC's in parallel with >>>> an ideal cap should do it. >>>> >>>> --sp >>>> >>>> >>>> -- Best regards, Spehro Pefhany >>> >>> Yes I have read the articles by Bob Pease but I need to be able to >>> measure and determine the equivalent circuit for a given capacitor so >>> that compensation can be applied. Each unit is hand adjusted. >> >> Yikes, that sounds like nailing jello to a tree. Do you have any reason >> to suppose that all the internal time constants would be >> temperature-independent? Cuz otherwise that's a nasty calibration table >> to create. > > Is there any reason to believe it will be linear with the voltage step? > (Sounds like a research project.) > > I thought I read once that teflon caps had low soakage. Maybe they > are better than polypropylene? * I thought i read that Teflon(TM) was rather good at holding a "reserve" charge after discharging, similar to glass (viz: CRT). An air or vacuum capacitor may be near the best WRT "soakage". > > George h. >> >> Cheers >> >> Phil Hobbs >> >> -- >> Dr Philip C D Hobbs >> Principal Consultant >> ElectroOptical Innovations LLC >> Optics, Electro-optics, Photonics, Analog Electronics >> >> 160 North State Road #203 >> Briarcliff Manor NY 10510 >> >> hobbs at electrooptical dot net >> http://electrooptical.net >
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| From | George Herold <gherold@teachspin.com> |
|---|---|
| Date | 2017-02-09 06:36 -0800 |
| Message-ID | <6d69c04c-8985-4e37-95a5-48bc43cc7b5a@googlegroups.com> |
| In reply to | #446968 |
On Wednesday, February 8, 2017 at 11:50:57 PM UTC-5, Robert Baer wrote: > George Herold wrote: > > On Wednesday, February 8, 2017 at 11:59:10 AM UTC-5, Phil Hobbs wrote: > >> On 02/08/2017 11:43 AM, Prof78 wrote: > >>> On Monday, 6 February 2017 13:57:52 UTC, Spehro Pefhany wrote: > >>>> On Mon, 6 Feb 2017 05:31:04 -0800 (PST), the renowned Prof78 > >>>> <scott.hamilton@manchester.ac.uk> wrote: > >>>> > >>>>> Looking for advice/experience on measurement of capacitor > >>>>> soakage. Would like to determine an approximate equivalent > >>>>> circuit for a 1uF polypropylene capacitor at very low > >>>>> frequency/time intervals of tens of seconds. > >>>>> > >>>>> Scott Hamilton. > >>>> > >>>> > >>>> Did you read Bob Pease's article? A bunch of RC's in parallel with > >>>> an ideal cap should do it. > >>>> > >>>> --sp > >>>> > >>>> > >>>> -- Best regards, Spehro Pefhany > >>> > >>> Yes I have read the articles by Bob Pease but I need to be able to > >>> measure and determine the equivalent circuit for a given capacitor so > >>> that compensation can be applied. Each unit is hand adjusted. > >> > >> Yikes, that sounds like nailing jello to a tree. Do you have any reason > >> to suppose that all the internal time constants would be > >> temperature-independent? Cuz otherwise that's a nasty calibration table > >> to create. > > > > Is there any reason to believe it will be linear with the voltage step? > > (Sounds like a research project.) > > > > I thought I read once that teflon caps had low soakage. Maybe they > > are better than polypropylene? > * I thought i read that Teflon(TM) was rather good at holding a > "reserve" charge after discharging, similar to glass (viz: CRT). > An air or vacuum capacitor may be near the best WRT "soakage". Check out the figure on page 301 of AoE3. We need Win to tell us which COG cap is brand X and which brand Y... George H. > > > > > > George h. > >> > >> Cheers > >> > >> Phil Hobbs > >> > >> -- > >> Dr Philip C D Hobbs > >> Principal Consultant > >> ElectroOptical Innovations LLC > >> Optics, Electro-optics, Photonics, Analog Electronics > >> > >> 160 North State Road #203 > >> Briarcliff Manor NY 10510 > >> > >> hobbs at electrooptical dot net > >> http://electrooptical.net > >
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| From | Phil Allison <pallison49@gmail.com> |
|---|---|
| Date | 2017-02-08 17:10 -0800 |
| Message-ID | <a0a551a9-7373-4cc5-9900-203f787c31b9@googlegroups.com> |
| In reply to | #446788 |
Prof78 wrote: > > Yes I have read the articles by Bob Pease but I need to be able to > measure and determine the equivalent circuit for a given capacitor > so that compensation can be applied. Each unit is hand adjusted. > > Scott Hamilton. ** Hi Scott: did you check the Wiki on DA ? There is a link there on modelling DA. http://www.designers-guide.org/Modeling/da.pdf Looks like what you are after. ..... Phil
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| From | Phil Allison <pallison49@gmail.com> |
|---|---|
| Date | 2017-02-06 06:51 -0800 |
| Message-ID | <c693d4ec-9d39-42c3-9660-c7242b7d591f@googlegroups.com> |
| In reply to | #446400 |
Prof78 wrote: > > > Looking for advice/experience on measurement of capacitor soakage. > Would like to determine an approximate equivalent circuit for a 1uF > polypropylene capacitor at very low frequency/time intervals of tens > of seconds. > > ** Surely you know polyprop caps have very low DA (dielectric absorption) ? The actual performance of examples will vary from one to another, from batch to batch and even with the cap's particular history. Mad to assume they are all the same. Leakage is just as variable too. Try polystyrene is you want to minimise that. ..... Phil
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| From | Prof78 <scott.hamilton@manchester.ac.uk> |
|---|---|
| Date | 2017-02-08 08:32 -0800 |
| Message-ID | <bae3a27c-829d-4970-8c63-014684d9b93b@googlegroups.com> |
| In reply to | #446415 |
On Monday, 6 February 2017 14:51:38 UTC, Phil Allison wrote: > Prof78 wrote: > > > > > > Looking for advice/experience on measurement of capacitor soakage. > > Would like to determine an approximate equivalent circuit for a 1uF > > polypropylene capacitor at very low frequency/time intervals of tens > > of seconds. > > > > > > ** Surely you know polyprop caps have very low DA (dielectric absorption) ? > > The actual performance of examples will vary from one to another, from batch to batch and even with the cap's particular history. > > Mad to assume they are all the same. > > Leakage is just as variable too. > > Try polystyrene is you want to minimise that. > > > > ..... Phil Yes I am aware of the variability but this is an extreme application where individual systems are hand adjusted to get the desired response.
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| From | Tim Wescott <seemywebsite@myfooter.really> |
|---|---|
| Date | 2017-02-08 17:48 -0600 |
| Message-ID | <DtqdnW6HLKLOMwbFnZ2dnUU7-IGdnZ2d@giganews.com> |
| In reply to | #446786 |
On Wed, 08 Feb 2017 08:32:50 -0800, Prof78 wrote: > On Monday, 6 February 2017 14:51:38 UTC, Phil Allison wrote: >> Prof78 wrote: >> > >> > >> > Looking for advice/experience on measurement of capacitor soakage. >> > Would like to determine an approximate equivalent circuit for a 1uF >> > polypropylene capacitor at very low frequency/time intervals of tens >> > of seconds. >> > >> > >> > >> ** Surely you know polyprop caps have very low DA (dielectric >> absorption) ? >> >> The actual performance of examples will vary from one to another, from >> batch to batch and even with the cap's particular history. >> >> Mad to assume they are all the same. >> >> Leakage is just as variable too. >> >> Try polystyrene is you want to minimise that. >> >> >> >> ..... Phil > > Yes I am aware of the variability but this is an extreme application > where individual systems are hand adjusted to get the desired response. Well, yes, but wouldn't it be better to shell out the cash for something that has minimal problems _first_, and _then_ go and hand-optimize it? And -- could you do better with a Really Good ADC attached to a Really Good voltage reference and a freaking plain-old-garden-variety microprocessor, that's talking to a Really Good DAC? Because I suspect that, within the confines of your Really Good Cap and the whole compensation network to make it Really Better, you could fit all the stuff that I'm talking about and have room left over for a small video game. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com I'm looking for work -- see my website!
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| From | "Tim Williams" <tiwill@seventransistorlabs.com> |
|---|---|
| Date | 2017-02-08 17:56 -0600 |
| Message-ID | <o7gb2o$nap$1@dont-email.me> |
| In reply to | #446786 |
"Prof78" <scott.hamilton@manchester.ac.uk> wrote in message news:bae3a27c-829d-4970-8c63-014684d9b93b@googlegroups.com... > Yes I am aware of the variability but this is an extreme application where > individual systems are hand adjusted to get the desired response. > Would it not be easier to DAQ everything and implement the filter with a sufficient number of DSP bits? Even with high dynamic range (>20 bits), if the bandwidth isn't terrifying (sub kHz?), it starts to look a whole lot better... Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
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