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Groups > sci.electronics.design > #446400 > unrolled thread

Capacitor soakage

Started byProf78 <scott.hamilton@manchester.ac.uk>
First post2017-02-06 05:31 -0800
Last post2017-02-08 17:56 -0600
Articles 20 on this page of 28 — 13 participants

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Contents

  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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#446400 — Capacitor soakage

FromProf78 <scott.hamilton@manchester.ac.uk>
Date2017-02-06 05:31 -0800
SubjectCapacitor soakage
Message-ID<b90d7cca-cbde-457c-9ef8-8e9ff14d941a@googlegroups.com>
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.

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#446404

FromSpehro Pefhany <speffSNIP@interlogDOTyou.knowwhat>
Date2017-02-06 08:57 -0500
Message-ID<m30h9c5ss1phtv430bo8din2koiovcl1fp@4ax.com>
In reply to#446400
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

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#446788

FromProf78 <scott.hamilton@manchester.ac.uk>
Date2017-02-08 08:43 -0800
Message-ID<21dd5db3-043e-4ab0-8706-4717052b4136@googlegroups.com>
In reply to#446404
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.
Scott Hamilton.

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#446794

FromPhil Hobbs <pcdhSpamMeSenseless@electrooptical.net>
Date2017-02-08 11:59 -0500
Message-ID<vq-dncrOcPvL0wbFnZ2dnUU7-K-dnZ2d@supernews.com>
In reply to#446788
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.

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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#446827

FromGeorge Herold <gherold@teachspin.com>
Date2017-02-08 10:30 -0800
Message-ID<02bf1a7f-7f88-4fc2-ad80-201abf1af6fa@googlegroups.com>
In reply to#446794
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

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#446829

FromPhil Hobbs <pcdhSpamMeSenseless@electrooptical.net>
Date2017-02-08 13:39 -0500
Message-ID<naqdnQgeLvpF-AbFnZ2dnUU7-R_NnZ2d@supernews.com>
In reply to#446827
On 02/08/2017 01:30 PM, 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.

Film caps are all pretty good--none of the common polymers is 
ferroelectric, so they don't saturate like titanates and so forth.

If I were doing it, I'd probably use a dynamic signal analyzer to 
measure the transfer function of an RC lowpass and let it run over the 
weekend.

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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#446849

FromJohn Larkin <jjlarkinxyxy@highlandtechnology.com>
Date2017-02-08 12:38 -0800
Message-ID<670n9ch6c0se4tvhhif0ejng5l3kojr1rj@4ax.com>
In reply to#446829
On Wed, 8 Feb 2017 13:39:32 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>On 02/08/2017 01:30 PM, 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.
>
>Film caps are all pretty good--none of the common polymers is 
>ferroelectric, so they don't saturate like titanates and so forth.
>
>If I were doing it, I'd probably use a dynamic signal analyzer to 
>measure the transfer function of an RC lowpass and let it run over the 
>weekend.
>
>Cheers
>
>Phil Hobbs


I'd time-domain it. Charge overnight, short briefly, log the
open-circuit voltage for a day or so. You'd need a low-bias-current
DVM or follower opamp.

There could be a huge range of internal tau's.

Someone here once posted long-term (months and years) leakage of some
charged film caps.


-- 

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement 

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

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#446860

FromPhil Hobbs <pcdhSpamMeSenseless@electrooptical.net>
Date2017-02-08 16:11 -0500
Message-ID<n_KdnZH4b9b9FAbFnZ2dnUU7-U2dnZ2d@supernews.com>
In reply to#446849
On 02/08/2017 03:38 PM, John Larkin wrote:
> On Wed, 8 Feb 2017 13:39:32 -0500, Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>> On 02/08/2017 01:30 PM, 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.
>>
>> Film caps are all pretty good--none of the common polymers is
>> ferroelectric, so they don't saturate like titanates and so forth.
>>
>> If I were doing it, I'd probably use a dynamic signal analyzer to
>> measure the transfer function of an RC lowpass and let it run over the
>> weekend.
>>
>> Cheers
>>
>> Phil Hobbs
>
>
> I'd time-domain it. Charge overnight, short briefly, log the
> open-circuit voltage for a day or so. You'd need a low-bias-current
> DVM or follower opamp.
>
> There could be a huge range of internal tau's.
>
> Someone here once posted long-term (months and years) leakage of some
> charged film caps.
>
>
I'd sort of expect leakage and tempco to make the analysis harder that 
way, though.

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

[toc] | [prev] | [next] | [standalone]

#447024

FromJohn Larkin <jjlarkin@highlandtechnology.com>
Date2017-02-09 08:30 -0800
Message-ID<226p9c1as7edo9obh4pcam1gip05v17fjo@4ax.com>
In reply to#446860
On Wed, 8 Feb 2017 16:11:08 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

>On 02/08/2017 03:38 PM, John Larkin wrote:
>> On Wed, 8 Feb 2017 13:39:32 -0500, Phil Hobbs
>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>
>>> On 02/08/2017 01:30 PM, 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.
>>>
>>> Film caps are all pretty good--none of the common polymers is
>>> ferroelectric, so they don't saturate like titanates and so forth.
>>>
>>> If I were doing it, I'd probably use a dynamic signal analyzer to
>>> measure the transfer function of an RC lowpass and let it run over the
>>> weekend.
>>>
>>> Cheers
>>>
>>> Phil Hobbs
>>
>>
>> I'd time-domain it. Charge overnight, short briefly, log the
>> open-circuit voltage for a day or so. You'd need a low-bias-current
>> DVM or follower opamp.
>>
>> There could be a huge range of internal tau's.
>>
>> Someone here once posted long-term (months and years) leakage of some
>> charged film caps.
>>
>>
>I'd sort of expect leakage and tempco to make the analysis harder that 
>way, though.
>
>Cheers
>
>Phil Hobbs

Leakage is just one more component of the circuit model, the 1st order
time constant. But a good film cap apparently leaks a fraction of a
per cent per year.

Capacitance tempco will change the voltage, so I guess it should be
tested at constant temperature. But then the OP will have to run the
actual thing at a constant temp if he expects to compensate to the
measured accuracy. 



-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics

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#447058

FromPhil Hobbs <pcdhSpamMeSenseless@electrooptical.net>
Date2017-02-09 14:55 -0500
Message-ID<o7ih9k$kcq$2@dont-email.me>
In reply to#447024
On 02/09/2017 11:30 AM, John Larkin wrote:
> On Wed, 8 Feb 2017 16:11:08 -0500, Phil Hobbs
> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>
>> On 02/08/2017 03:38 PM, John Larkin wrote:
>>> On Wed, 8 Feb 2017 13:39:32 -0500, Phil Hobbs
>>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>>
>>>> On 02/08/2017 01:30 PM, 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.
>>>>
>>>> Film caps are all pretty good--none of the common polymers is
>>>> ferroelectric, so they don't saturate like titanates and so forth.
>>>>
>>>> If I were doing it, I'd probably use a dynamic signal analyzer to
>>>> measure the transfer function of an RC lowpass and let it run over the
>>>> weekend.
>>>>
>>>> Cheers
>>>>
>>>> Phil Hobbs
>>>
>>>
>>> I'd time-domain it. Charge overnight, short briefly, log the
>>> open-circuit voltage for a day or so. You'd need a low-bias-current
>>> DVM or follower opamp.
>>>
>>> There could be a huge range of internal tau's.
>>>
>>> Someone here once posted long-term (months and years) leakage of some
>>> charged film caps.
>>>
>>>
>> I'd sort of expect leakage and tempco to make the analysis harder that
>> way, though.
>>
>> Cheers
>>
>> Phil Hobbs
>
> Leakage is just one more component of the circuit model, the 1st order
> time constant. But a good film cap apparently leaks a fraction of a
> per cent per year.
>
> Capacitance tempco will change the voltage, so I guess it should be
> tested at constant temperature. But then the OP will have to run the
> actual thing at a constant temp if he expects to compensate to the
> measured accuracy.

I'd be very surprised if he didn't have to in any event, since the sorts 
of relaxation processes that give rise to soakage must have fairly 
dramatic temperature dependences.

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

[toc] | [prev] | [next] | [standalone]

#446894

Frombill.sloman@ieee.org
Date2017-02-08 14:53 -0800
Message-ID<570d2194-7079-4833-aae9-3b951c1e57d9@googlegroups.com>
In reply to#446829
On Thursday, February 9, 2017 at 5:39:29 AM UTC+11, Phil Hobbs wrote:
> On 02/08/2017 01:30 PM, 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.
> 
> Film caps are all pretty good--none of the common polymers is 
> ferroelectric, so they don't saturate like titanates and so forth.

Film cap charge soak does vary with dielectric - polyester gives the worst charge soak, and polycarbonate isn't much better. Polypropylene is roughly an order of magnitude better. Telflon is reputed to be better still - but hard to get hold and expensive.

Polystyrene is supposed to be good, but offers a lot less capacitance per unit volume.

-- 
Bill Sloman, Sydney

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#446921

FromSpehro Pefhany <speffSNIP@interlogDOTyou.knowwhat>
Date2017-02-08 19:11 -0500
Message-ID<62an9cphnm0aqtvo4o9ph8bkmu1r4ros63@4ax.com>
In reply to#446894
On Wed, 8 Feb 2017 14:53:06 -0800 (PST), the renowned
bill.sloman@ieee.org wrote:
>
>Film cap charge soak does vary with dielectric - polyester gives the worst charge soak, and polycarbonate isn't much better. Polypropylene is roughly an order of magnitude better. Telflon is reputed to be better still - but hard to get hold and expensive.
>
>Polystyrene is supposed to be good, but offers a lot less capacitance per unit volume.

Some of the newer dielectrics that can withstand reflow soldering
temperatures are not too bad. PPS (Polyphenylene sulfide), for
example. 

--sp 

-- 
Best regards, 
Spehro Pefhany

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#446891

FromFrank Miles <fpm@u.washington.edu>
Date2017-02-08 22:36 +0000
Message-ID<o7g6hg$1v2$1@dont-email.me>
In reply to#446827
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.

Mylar is definitely bad; polycarbonates not great either.  Polypropylene is
good, perhaps nearly as good as the ever-meltable polystyrene.

The ceramics are mostly mediocre (or worse), though some of the newer C0Gs are 
close to polypropylene.

Ah yes... got me to look it up in AoE3(p301): mostly what I've been sayin',
except for the PTFE!  This may be another case like the C0Gs - i.e. dependent
on manufacturer/unknown parameters.

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#446945

FromGeorge Herold <gherold@teachspin.com>
Date2017-02-08 17:48 -0800
Message-ID<45ccbaec-d040-4b95-8011-599f8d72c5a8@googlegroups.com>
In reply to#446891
On Wednesday, February 8, 2017 at 5:38:23 PM UTC-5, cassiope 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.
> 
> Mylar is definitely bad; polycarbonates not great either.  Polypropylene is
> good, perhaps nearly as good as the ever-meltable polystyrene.
> 
> The ceramics are mostly mediocre (or worse), though some of the newer C0Gs are 
> close to polypropylene.
> 
> Ah yes... got me to look it up in AoE3(p301): mostly what I've been sayin',
> except for the PTFE!  This may be another case like the C0Gs - i.e. dependent
> on manufacturer/unknown parameters.

My copy of AoE3 is at work,  I've never used teflon so I have no idea
in practice.  (The one time I went looking for teflon caps, 
they seemed to be part of audio-foolery and over priced.)
Yeah, there are some "good" C0G's?  I seem to recall the B. Pease plot 
with some good and bad ceramics.  All the new cog/npo that I've used 
have been fine wrt DF, loss in some LC resonant circuit.
That might, or might not, relate to DA.     

George H.

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#447046

FromJohn Larkin <jjlarkinxyxy@highlandtechnology.com>
Date2017-02-09 11:17 -0800
Message-ID<i0gp9c9kcsukm6mikhie7d6nrldeh0arhu@4ax.com>
In reply to#446945
On Wed, 8 Feb 2017 17:48:07 -0800 (PST), George Herold
<gherold@teachspin.com> wrote:

>On Wednesday, February 8, 2017 at 5:38:23 PM UTC-5, cassiope 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.
>> 
>> Mylar is definitely bad; polycarbonates not great either.  Polypropylene is
>> good, perhaps nearly as good as the ever-meltable polystyrene.
>> 
>> The ceramics are mostly mediocre (or worse), though some of the newer C0Gs are 
>> close to polypropylene.
>> 
>> Ah yes... got me to look it up in AoE3(p301): mostly what I've been sayin',
>> except for the PTFE!  This may be another case like the C0Gs - i.e. dependent
>> on manufacturer/unknown parameters.
>
>My copy of AoE3 is at work,  I've never used teflon so I have no idea
>in practice.  (The one time I went looking for teflon caps, 
>they seemed to be part of audio-foolery and over priced.)
>Yeah, there are some "good" C0G's?  I seem to recall the B. Pease plot 
>with some good and bad ceramics.  All the new cog/npo that I've used 
>have been fine wrt DF, loss in some LC resonant circuit.
>That might, or might not, relate to DA.     
>
>George H. 

Vacuum capacitors have pretty low DA.

We need a high-K vacuum.


-- 

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement 

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

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#447089

From"Tim Williams" <tiwill@seventransistorlabs.com>
Date2017-02-09 16:46 -0600
Message-ID<o7irc4$sid$1@dont-email.me>
In reply to#447046
"John Larkin" <jjlarkinxyxy@highlandtechnology.com> wrote in message 
news:i0gp9c9kcsukm6mikhie7d6nrldeh0arhu@4ax.com...
> Vacuum capacitors have pretty low DA.
>
> We need a high-K vacuum.

If you make the plates out of neutronium, that might help out.

As a bonus, it may be a high temperature superconductor, which is nice.

As a downside, it'll have lower energy storage capacity -- y'know, too much 
and the whole thing collapses.  Pesky, that.

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com

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#447127

Fromkrw@notreal.com
Date2017-02-09 20:44 -0500
Message-ID<5l6q9c9admkcuo163uheifrao6utbfeu42@4ax.com>
In reply to#447089
On Thu, 9 Feb 2017 16:46:22 -0600, "Tim Williams"
<tiwill@seventransistorlabs.com> wrote:

>"John Larkin" <jjlarkinxyxy@highlandtechnology.com> wrote in message 
>news:i0gp9c9kcsukm6mikhie7d6nrldeh0arhu@4ax.com...
>> Vacuum capacitors have pretty low DA.
>>
>> We need a high-K vacuum.
>
>If you make the plates out of neutronium, that might help out.

How do the plates change the permativity of the dielectric?
>
>As a bonus, it may be a high temperature superconductor, which is nice.
>
>As a downside, it'll have lower energy storage capacity -- y'know, too much 
>and the whole thing collapses.  Pesky, that.
>
>Tim

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#447138

Frombill.sloman@ieee.org
Date2017-02-09 19:15 -0800
Message-ID<9d7fe0a5-f849-4caf-a1d3-a447213acc45@googlegroups.com>
In reply to#447127
On Friday, February 10, 2017 at 12:44:57 PM UTC+11, k...@notreal.com wrote:
> On Thu, 9 Feb 2017 16:46:22 -0600, "Tim Williams"
> <tiwill@seventransistorlabs.com> wrote:
> 
> >"John Larkin" <jjlarkinxyxy@highlandtechnology.com> wrote in message 
> >news:i0gp9c9kcsukm6mikhie7d6nrldeh0arhu@4ax.com...
> >> Vacuum capacitors have pretty low DA.
> >>
> >> We need a high-K vacuum.
> >
> >If you make the plates out of neutronium, that might help out.
> 
> How do the plates change the permativity of the dielectric?

The empty space between the plates would be intensely curved (high gravitational field), and the geometry non-Euclidian.

Sadly, empty space next to neutronium isn't going to stay empty long - it won't last any longer than the neutronium which doesn't seem to be stable anywhere except inside a star with at least 20% of mass of the sun.

> >As a bonus, it may be a high temperature superconductor, which is nice.
> >
> >As a downside, it'll have lower energy storage capacity -- y'know, too much 
> >and the whole thing collapses.  Pesky, that.

Not really. It would probably explode before you could get the bits close enough together to collapse.

-- 
Bill Sloman, Sydney

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#447140

FromJohn Larkin <jjlarkin@highlandtechnology.com>
Date2017-02-09 20:54 -0800
Message-ID<nnhq9clbnog9o93t86htg7906hnqomn941@4ax.com>
In reply to#447089
On Thu, 9 Feb 2017 16:46:22 -0600, "Tim Williams"
<tiwill@seventransistorlabs.com> wrote:

>"John Larkin" <jjlarkinxyxy@highlandtechnology.com> wrote in message 
>news:i0gp9c9kcsukm6mikhie7d6nrldeh0arhu@4ax.com...
>> Vacuum capacitors have pretty low DA.
>>
>> We need a high-K vacuum.
>
>If you make the plates out of neutronium, that might help out.
>
>As a bonus, it may be a high temperature superconductor, which is nice.
>
>As a downside, it'll have lower energy storage capacity -- y'know, too much 
>and the whole thing collapses.  Pesky, that.
>
>Tim

Some sort of multiple-parallel-plate MEMS vacuum cap should be
possible, with really tiny plate spacing. But MIS SiO2 caps are really
good. Those are used inside ICs to make capacitive ADCs and such.


-- 

John Larkin         Highland Technology, Inc

lunatic fringe electronics

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#447044

FromJohn Larkin <jjlarkinxyxy@highlandtechnology.com>
Date2017-02-09 11:16 -0800
Message-ID<8hfp9clut054993n5tqokis9e5qr57lf6a@4ax.com>
In reply to#446891
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.

>
>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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