In article ,
Telamon wrote:
In article ,
(Mark Zenier) wrote:

In article ,
Al Arduengo wrote:

If it says mfd it should mean mili-farads - not micro-farads.

Nobody uses millifarads, except maybe the boom car crowd. "mfd" or more
commonly "mf", prior to (the 1960's) metrification/SI rationalization
meant Microfarads. And picofarads were "mmf" micro micro farads.

Mark Zenier Washington State resident

That's not what I see in most articles or catalogs.
1 F is 1 farad
1 mF is .001 or 1x10^ -3 or 1 milli-farad
1 uF is .000,001 or 1 x 10^ -6 or 1 micro-farad
1 nF is .000,000,001 or 1 x 10^ -9 or 1 nano-farad
1 pF is .000,000,000,001 or 1 x 10^ -12 or 1 pico-farad

Many capacitors are in mF in industrial power supplies. Got to get the
current step response down to 20 Hz in some cases.

Man, I just dug out an older EEM (Electronics Engineers Master catalog)
and it's a MESS. Even in 1993, some outfits were still using MFD for
microfarads.

Millifarads are probably an artifact of Globalization (ie. of the outfits
that used MFD for uF in 1993 are probably now empty factories in the
US midwest after all their equipment got auctioned off to somebody
from Canton). Likewise nanofarads are pretty much of an indicator the
your capacitor was made by a European based manufacturer.

I'd only expect to see millifarads on big "Computer Electrolytics",
those beer can size (or bigger) with screw terminals.

The bottom line for project building hobbyists is that you need to take
into account when and where the magazine article or book was written.
There's a lot of stuff out there that's old enough to be really confusing.
(Several years back, I had an e-mail converstation with a guy who was
trying to find parts for a transistorized VLF reciever, and the writeup
included how to use it for detecting atmospheric atomic bomb tests,
which quit before 1963).

Mark Zenier Washington State resident

In article .com,
wrote:
Thanks for the replies... So what does 50,000 mfd translate to in uF?
..5? .05?

50,000 uF. Probably about the size of small can of V8 juice, given the
voltage rating you'd use in a car (16 or 25 volts?). The newer they are,
the smaller they get, so I might be showing my age.

Mark Zenier Washington State resident

Today mF most often means millifarad.
But in years past mF meant micro,
as in uF, farad.
Some diagrams as recent as the late 1990s
still used mF to equal uF.
Conversly, before the mid 1990s, no one but
the military EMP research labs had Farad or
milliFarad caps. I still remember when I saw
my first .47F capacitor. Kind of freaked me out.
I used a couple of 0.47 caps to replace the
lithium backup cells in my R2000 and my IC-28A.
If I had a few $100 to spare, I would be temtped to
buy one of the several Farad caps designed for the
automotive crowd. A cap that size would allow me
to coast through most power glitches.
Terry

m II wrote:

Al Arduengo wrote:

mfd=Microfarads or uF. In other words buy yourself a nice big
electrolytic cap (about 30wvdc for make sure it surives) and put it
across the leads. Get it at Ratshack, or any electronic parts
supplier.


If it says mfd it should mean mili-farads - not micro-farads.

Not in the USA.

It seems the times are changing. 'Mfd' has always meant micro-farads in
the US but with the large capacitors being made now, 'uf' is becoming a
better notation so it's not confused with 'milli-farads' for the big
caps'.

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Mark Zenier ) writes:
In article .com,
wrote:
Thanks for the replies... So what does 50,000 mfd translate to in uF?
..5? .05?

50,000 uF. Probably about the size of small can of V8 juice, given the
voltage rating you'd use in a car (16 or 25 volts?). The newer they are,
the smaller they get, so I might be showing my age.

The first power supply I built, in the early seventies, I bought at
a hamfest a 10,000uF capacitor with about a 16v rating. Big stuff at
the time. It's the size of a Coke can, and has those screw terminals.
"Computer grade" was what similar capacitors in the surplus store
ads were called.

Pretty useless these days, given that you can get bigger capacitance
and a higher voltage rating in a much smaller package.

Micahel

Thanks Mark! I got my noise filter today and will get it hooked up
this weekend. I'm hopeful that it resolves the alternator whine by
iteself, but I expect it will take a cap to totally fix it.