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#1
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Polystyrene capacitors for filter networks?
Hi,
They look worryingly inductive on visual inspection (there are metal foils rolled up in thar by the look of it.) And yet the CPC catalogue says that their properties make them ideal for use in filters. Has anyone any remarks (favourable or otherwise) to make about the use of this type of cap in filter apps? p. -- The BBC: Licensed at public expense to spread lies. |
#2
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Hi Paul!
There are non-inductively wound ones specifically for the purpose. The mfr. specs should show an ESR curve - the non-inductive ones are pretty flat to their SRF. -- Gregg *It's probably useful, even if it can't be SPICE'd* http://geek.scorpiorising.ca |
#3
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On Wed, 17 Mar 2004 12:30:56 GMT, Gregg wrote:
Hi Paul! There are non-inductively wound ones specifically for the purpose. The mfr. specs should show an ESR curve - the non-inductive ones are pretty flat to their SRF. I notice some of them come with one end tinted red (or sometimes black). Does this indicate the non inductively-wound type? -- The BBC: Licensed at public expense to spread lies. |
#4
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Behold, Paul Burridge signalled from keyed 4-1000A filament:
On Wed, 17 Mar 2004 12:30:56 GMT, Gregg wrote: Hi Paul! There are non-inductively wound ones specifically for the purpose. The mfr. specs should show an ESR curve - the non-inductive ones are pretty flat to their SRF. I notice some of them come with one end tinted red (or sometimes black). Does this indicate the non inductively-wound type? Nope. That just indicates the "outside" foil - commonly goes to ground. -- Gregg *It's probably useful, even if it can't be SPICE'd* http://geek.scorpiorising.ca |
#5
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Behold, Paul Burridge signalled from keyed 4-1000A filament:
On Wed, 17 Mar 2004 12:30:56 GMT, Gregg wrote: Hi Paul! There are non-inductively wound ones specifically for the purpose. The mfr. specs should show an ESR curve - the non-inductive ones are pretty flat to their SRF. I notice some of them come with one end tinted red (or sometimes black). Does this indicate the non inductively-wound type? Nope. That just indicates the "outside" foil - commonly goes to ground. -- Gregg *It's probably useful, even if it can't be SPICE'd* http://geek.scorpiorising.ca |
#6
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On Wed, 17 Mar 2004 12:30:56 GMT, Gregg wrote:
Hi Paul! There are non-inductively wound ones specifically for the purpose. The mfr. specs should show an ESR curve - the non-inductive ones are pretty flat to their SRF. I notice some of them come with one end tinted red (or sometimes black). Does this indicate the non inductively-wound type? -- The BBC: Licensed at public expense to spread lies. |
#7
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"Paul Burridge" wrote in message ... Hi, They look worryingly inductive on visual inspection (there are metal foils rolled up in thar by the look of it.) And yet the CPC catalogue says that their properties make them ideal for use in filters. Has anyone any remarks (favourable or otherwise) to make about the use of this type of cap in filter apps? They are OK for LF filters, the inductance won't make any appreciable difference and they are available with 1% tolerance. They are getting difficult to find. They are also useful for RF oscillators. Leon |
#8
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"Paul Burridge" wrote in message ... | Hi, | | They look worryingly inductive on visual inspection (there are metal | foils rolled up in thar by the look of it.) And yet the CPC catalogue | says that their properties make them ideal for use in filters. Has | anyone any remarks (favourable or otherwise) to make about the use of | this type of cap in filter apps? | | p. | -- | | The BBC: Licensed at public expense to spread lies. Silly boy...... Go and find out about construction methods. The metallisation is offset so the end terminations parallel the internal layers. DNA |
#9
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On Wed, 17 Mar 2004 15:45:34 -0000, the renowned "Emoneg"
wrote: "Paul Burridge" wrote in message .. . | Hi, | | They look worryingly inductive on visual inspection (there are metal | foils rolled up in thar by the look of it.) And yet the CPC catalogue | says that their properties make them ideal for use in filters. Has | anyone any remarks (favourable or otherwise) to make about the use of | this type of cap in filter apps? | | p. | -- | | The BBC: Licensed at public expense to spread lies. Silly boy...... Go and find out about construction methods. The metallisation is offset so the end terminations parallel the internal layers. DNA Yup. Take two sheets of letter-size (okay, A4) paper and lay one on top of the other but the top one to the right by 1/2". These are like the plates of your capacitor. Now roll them up from the bottom to the top into a tight roll. Imagine you connect to all the right end (in parallel) by dipping it in some conductive goop, and call that lead A. Do the same to the left, and call it lead B. The coiled construction adds no inductance. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com |
#10
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On Wed, 17 Mar 2004 15:45:34 -0000, the renowned "Emoneg"
wrote: "Paul Burridge" wrote in message .. . | Hi, | | They look worryingly inductive on visual inspection (there are metal | foils rolled up in thar by the look of it.) And yet the CPC catalogue | says that their properties make them ideal for use in filters. Has | anyone any remarks (favourable or otherwise) to make about the use of | this type of cap in filter apps? | | p. | -- | | The BBC: Licensed at public expense to spread lies. Silly boy...... Go and find out about construction methods. The metallisation is offset so the end terminations parallel the internal layers. DNA Yup. Take two sheets of letter-size (okay, A4) paper and lay one on top of the other but the top one to the right by 1/2". These are like the plates of your capacitor. Now roll them up from the bottom to the top into a tight roll. Imagine you connect to all the right end (in parallel) by dipping it in some conductive goop, and call that lead A. Do the same to the left, and call it lead B. The coiled construction adds no inductance. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com |
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