[Test-Equipment] ESR meter

[Ken Kaplan]

Hi Richard,

Good write-up on caps. I'm sure it was helpful to many on the list. My 
question was about the etymology of the word electrolytic. I wasn't sure 
how the suffix "lytic" applies. I have since found an explanation. 
Electrolytic relates to something using electrolytes. Simple.

I suppose all of this was ironed out by old guys back in the 1800's. 
I've often thought that regardless of how much I now know (I are an 
engineer), I'd be rather useless if I traveled back far enough in time 
with just the knowledge in my head. Might even get myself in trouble :-)

Regards,
Ken Kaplan
kb7rgg
(also from LA but living in AZ)

On 6/29/2011 1:22 AM, Richard Knoppow wrote:
>
> ----- Original Message -----
> From: "Ken Kaplan"<krkaplan at cox.net>
> To:<ka4inm at tampabay.rr.com>; "Discussion of Electronic Test
> Equipment"<test-equipment at mailman.qth.net>
> Sent: Tuesday, June 28, 2011 8:48 PM
> Subject: Re: [Test-Equipment] ESR meter
>
>> Not sure where the term "electrostatic capacitor"
>> originated but that's
>> what they are called in the Sprague TO-6A manual. As
>> Sprague knows a
>> little sumthin 'bout capacitors, I thought I'd use the
>> term.
>>
>> Now that we are talking about it, what does the suffix
>> lytic mean with
>> regards to electrolytic? The electro part I have (I
>> think).
>>
>> Maybe I should replace all those electrostatic caps in my
>> receivers with
>> electroquiet ones? All these years I thought that noise
>> was in the aether.
>>
>> Ken
>>
>       All capacitors are electrostatic just as all inductors
> are electromagnetic. The lytic in electrolytic comes from
> the use of a chemical solution to generate the dielectric
> layer under the influence of voltage by means of
> electrolysis. It is this electrolytic action that explains
> why electrolytic capacitors are polarized, the dielectric
> forms in the right place only when the current passes
> through the capacitor in the correct direction. The
> requirement for an electric current to form the dielectric
> layer also explains some of the problems electrolytic
> capacitors have when they are not used for a long period of
> time. Electrolytic capacitors have the advantage over fixed
> dielectric types in being comparatively small for their
> capacitance. However, even the best of them has relatively
> high leakage, that is parallel resistance, in comparison to
> other types. In many applications this is of minor
> significance compared to the large capacitance value
> possible.
>       In the past the main dielectric used in capacitors were
> air, special paper, selected types of mica, and ceramic
> materials of certain sorts. Paper capacitors were often
> impregnated with oil. The oil increased the dielectric
> constant and breakdown resistance allowing a higher voltage
> rating. Very high quality capacitors for high voltage use
> especially were sealed in cans with oil. The oil was similar
> to transformer oil but originally plain mineral oil was
> often used.
>       Paper capacitors were also frequently impregnated with
> wax and the enclosure was sealed and coated with wax. The
> wax helped to prevent the entry of subsequent absorption of
> moisture by the paper in the capacitor, moisture leading to
> a breakdown of the paper.
>       Mica capacitors were of two general types: silvered
> mica, and stacked mica. The former had the electrodes formed
> by electroplating the mica with silver except at the edges.
> The silvered mica plates were stacked in a sealed enclosure
> and the leads were directly soldered to the end plate.
> Stacked mica caps had separate foil electrodes interleaved
> with the mica dielectric, the entire assembly being held
> under pressure and sealed in a case. Silvered mica caps can
> be made to  a very high standard of accuracy and stacked
> mica caps were capable of being made to withstand very high
> voltages and were often used in transmitter.
>       Other types of capacitors were vacuum types used mostly
> in very high voltage circuits like the plate circuits of
> vacuum tube transmitters. They are less likely to arc over
> under conditions of high humidity than air capacitors.
>       Modern capacitors use a plastic film as the dielectric.
> The film is plated with the electrode in a way similar
> silvered mica capacitors but the form is similar to the old
> paper types, that is a long strip of plastic is coated on
> both sides and rolled up into a cylinder, the leads being
> fastened to the plating on the two sides. There are various
> techniques of winding the element to reduce stray
> inductance. These caps have very low leakage, very low ESR,
> and are much more accurate and stable than the older paper
> types.
>       There are some web sites with much more on electrolytic
> capacitors including a description of the various types with
> their virtues and vices.
>       All of this is very over simplified but much more
> detailed information is available on the web.
>
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickburk at ix.netcom.com