I keep seeing caps described as "computer grade" but a search for a
definition comes up with zilch.

What does this mean? As the vast majority of computers are owned by the
masses, one could assume it means sleazy consumer quality. Or it could
mean the kind of computer that prevents ICBM's from being accidentally
launched.

Which is it?

JACK K9ACT

--
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Jack Schmidling wrote:
I keep seeing caps described as "computer grade" but a search for a
definition comes up with zilch.

What does this mean? As the vast majority of computers are owned by the
masses, one could assume it means sleazy consumer quality. Or it could
mean the kind of computer that prevents ICBM's from being accidentally
launched.

Which is it?

JACK K9ACT

The name has been around for much longer than PC's, so I assume that it
means _mainframe_ computer grade -- today we'd say "server grade", I guess.

At any rate, if it has no legal meaning then it could be a total lie and
no one would be subject to any legal penalties (marketplace penalties
are another matter).

I have always taken it to mean _really_ _good_, but you'd have to go
over the specs to see, then extend some trust to the manufacturer.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google? See http://cfaj.freeshell.org/google/

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" gives you just what it says.
See details at http://www.wescottdesign.com/actfes/actfes.html

On Mon, 30 Apr 2007 06:28:17 -0600, Jack Schmidling wrote:


What does this mean?

Not a lot. It is just one of those meaningless terms
like military spec.

This is what passes for 'computer grade' these days:
http://www.badcaps.net/ident/

73, Ed. EI9GQ.

--
Linux 2.6.18

Jack Schmidling ) writes:
I keep seeing caps described as "computer grade" but a search for a
definition comes up with zilch.

What does this mean? As the vast majority of computers are owned by the
masses, one could assume it means sleazy consumer quality. Or it could
mean the kind of computer that prevents ICBM's from being accidentally
launched.

The term was around in the early seventies, at least. That was when
solid state was still relatively new, and electrolytics were not
as advanced as nowadays. I built 1A power supply in the fall of 1972,
and had found at a hamfest a "computer grade" electrolytic, in a
metal can,10,000uF at about 20 volts. It was about the size of a Coke can.
It was pretty massive in terms of capacitance at the time, the regular
electrolyitics were hard to find in such large values, and even this
one was barely sufficient in terms of voltage rating.

It was obviously surplus, from mainframe computers. I have no clue
whether they were particularly better than the regular electrolyitics,
but they were obviously the source for larger value filter caps at
the time. I'm sure some of it was merely hype, at the very least
"computer grade" says where the capacitors came from.

It's obviously different now. I can easily get 10,000uF electrolytics
in a far smaller package and with a bigger voltage rating. I haven't
evne noticed the term in a long time, other than the occasional question
about the term (it has come up before here or in one of the
sci.electronics.* newsgroups.

There obviously are different grades of electrolytics, with things
like temperature rating being important in some applications, and ESR
being important in others (especially things like switching supplies
where they have to deal with higher frequency waveforms). But
the talk is in terms of their specs, rather than some mythical
"computer grade" capacitor.

Michael VE2BVW

"Jack Schmidling" wrote in message
...
I keep seeing caps described as "computer grade" but a search for a
definition comes up with zilch.

What does this mean? As the vast majority of computers are owned by the
masses, one could assume it means sleazy consumer quality. Or it could
mean the kind of computer that prevents ICBM's from being accidentally
launched.

Which is it?

JACK K9ACT

I first ran into computer grade caps back in the 1970's, back when I was
building my first homebuilt computer (before the masses owned computers), I
considered it a pejorative, in that it was only good for building power
supplies for computers. Would it be be better if it said low voltage dc
power supply caps? Those big coke can sized caps made great smoothing caps,
along with some smaller caps they could knock ripple down to where you
needed an oscope to see it. Just don't build a supply with that as the only
cap on the output, they are ok on low freq swings, but also add a 1k and 10
uf cap to help clean up the rest of the ripple.
thanks John.
KC5DWD

On Mon, 30 Apr 2007 06:28:17 -0600, Jack Schmidling
wrote:

I keep seeing caps described as "computer grade" but a search for a
definition comes up with zilch.

In the 1960/70's computers were the only application requiring very
low voltage stabilised DC power supplies, +5 V for TTL, +6 V for DTL
and -5.2 V for ECL. Other high power DC applications in those days,
such as industrial automation, used 24 V, but relays weren't sensitive
to ripple or voltage variations.

When a typical computer consumed several kW at 5/6 V, quite huge DC
currents were required and thus the power supply capacitance in linear
power supplies had to be huge.

I have seen this "computer grade" term used in the 1970's when some
surplus companies tried to sell some huge size capacitors, when
physically smaller capacitors became available with the same
capacitance, in order to justify the size of the surplus units.

But after the 1970's I have never seen the term "computer grade" used.

Paul OH3LWR

In article ,
Jack Schmidling wrote:
I keep seeing caps described as "computer grade" but a search for a
definition comes up with zilch.

What does this mean? As the vast majority of computers are owned by the
masses, one could assume it means sleazy consumer quality. Or it could
mean the kind of computer that prevents ICBM's from being accidentally
launched.

Which is it?

Digging out the 1968 Newark catalog, on page 332 are the Mallory CG
series of big can capacitors in a section titled "Computer Grade
Electrolytic Capacitors". ie -10+75% tolerance, -40/+85 deg C temp.
$10 was a lot for a capacitor in 1968.

Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)

"Paul Keinanen" wrote in message
...
On Mon, 30 Apr 2007 06:28:17 -0600, Jack Schmidling
wrote:

I keep seeing caps described as "computer grade" but a search for a
definition comes up with zilch.

In the 1960/70's computers were the only application requiring very
low voltage stabilised DC power supplies, +5 V for TTL, +6 V for DTL
and -5.2 V for ECL. Other high power DC applications in those days,
such as industrial automation, used 24 V, but relays weren't sensitive
to ripple or voltage variations.

When a typical computer consumed several kW at 5/6 V, quite huge DC
currents were required and thus the power supply capacitance in linear
power supplies had to be huge.

I have seen this "computer grade" term used in the 1970's when some
surplus companies tried to sell some huge size capacitors, when
physically smaller capacitors became available with the same
capacitance, in order to justify the size of the surplus units.

But after the 1970's I have never seen the term "computer grade" used.

Paul OH3LWR


The term "computer grade" is in use today. See
http://www.mouser.com/catalog/629/576.pdf
and
http://www.mouser.com/catalog/629/574.pdf
for examples of those currently manufactured by Vishay/Sprague and
Mallory/CDE.

I suspect that the term "computer grade" signifies capacitors with screw
terminals. However, I can't prove it.

Cheers,
John

"Computer Grade Capacitor" might possibly refer to the low value of internal
series resistance and inductance which are important parameters in switching
regulator power supplies.

Bill W0IYH

"Mark Zenier" wrote in message
...
In article ,
Jack Schmidling wrote:
I keep seeing caps described as "computer grade" but a search for a
definition comes up with zilch.

What does this mean? As the vast majority of computers are owned by the
masses, one could assume it means sleazy consumer quality. Or it could
mean the kind of computer that prevents ICBM's from being accidentally
launched.

Which is it?

Digging out the 1968 Newark catalog, on page 332 are the Mallory CG
series of big can capacitors in a section titled "Computer Grade
Electrolytic Capacitors". ie -10+75% tolerance, -40/+85 deg C temp.
$10 was a lot for a capacitor in 1968.

Mark Zenier
Googleproofaddress(account:mzenier provider:eskimo domain:com)

William E. Sabin wrote:
"Computer Grade Capacitor" might possibly refer to the low value of internal
series resistance and inductance which are important parameters in switching
regulator power supplies.

Well, maybe "low inductance" by 1960's standards. A computer power
supply would have to filter 60Hz, or maybe 400Hz ripple then. Yes,
there were switching supplies back in the 60's/70's too, but then
switching frequencies were much much lower (think about it: they used
2N3055's or their predecessors, transistors that take a millenium to
turn off!) than typical switching supplies today.

Modern low-ESR low-inductance caps are undoubtedly superior if you're
designing 150kHz switching supplies today. Heck, many of the modern
regulator chips will only be stable if they are operated into
capacitors that have an ESR above a minimum and below a maximum
number. There's a reason why there are 87 different 220uF 6.3V
capacitors in the Digikey catalog :-).

Clearly for their purposes, surplus 2N3055's and old big-can "computer
grade capacitors" can be put to very good use in many ham power
supplies. Make sure you get some LM723's too, a very versatile part
that modern parts (each good in their own narrow niche) have not
completely replaced yet!

(I did lament here on Usenet when the CA3046 was discontinued a year
or two ago... a shame! But the LM723 will outlive it!)

Tim.