[sci.electronics] Metric Prefixes

yoshi@nocusuhs.nnmc.navy.mil (Dojun Yoshikami) (03/25/91)

Now let's see if I get this right.  I was looking in the All Electronics
catalog at the capacitors.  I was looking for some things around .1-micro
farad.  Now everything is listed in MFD.  I guess that M means mille.
It can't mean MEGA because I can't imagine anyone selling MEGA-FARAD
capacitors in such a variety of sizes (that would be a shocking experience).
As far as I can tell, Micro is usually written with a greek `Mu'.  What puzzles 
me is micro-farad sizes are VERY common, so does MFD refer to Micro-FaraD -- 
i.e. their typesetter can't set a `Mu'?  And to make things more confusing 
mille (10^-3) is usually written with a little `m'.  Now then they have some
mylar capacitors without any range (FD, MFD, Micro-FD, pfd), only numbers --
are these in Micro-FD?

In case anyone is wondering, I decided the best resolution to this quandary
was to order stuff from Newark instead.

DY ;-)

mcovingt@athena.cs.uga.edu (Michael A. Covington) (03/26/91)

Ah, you must be too young.

mf = mfd = uF = microfarad

mmf = mmfd = pF = picofarad (micro-microfarad)

If the capacitor is identified with just a number, it could be
any of three things:

(1) On an electrolytic (including tantalum) capacitor,
it's the value in uF.

(2) On anything smaller it's likely to be the value in pF.

(3) If it's 3 digits the 3rd of which is not 0
(for example 472) then it's picofarads and means 47E2, i.e., 47x10^2,
or 4700.

Just to really confuse you, 470 could mean 470, or 47 x 10^0 = 47.

-- 
-------------------------------------------------------
Michael A. Covington | Artificial Intelligence Programs
The University of Georgia  |  Athens, GA 30602   U.S.A.
-------------------------------------------------------

wb8foz@mthvax.cs.miami.edu (David Lesher) (03/26/91)

mcovingt@athena.cs.uga.edu (Michael A. Covington) writes:

>Ah, you must be too young.
>mf = mfd = uF = microfarad
>mmf = mmfd = pF = picofarad (micro-microfarad)
>If the capacitor is identified with just a number, it could be
>any of three things:

4) Nanofarads. A new invention. Just when you thought it was
safe to go back in the parts store :-]

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jfw@ksr.com (John F. Woods) (04/02/91)

yoshi@nocusuhs.nnmc.navy.mil (Dojun Yoshikami) writes:
>Now let's see if I get this right.  I was looking in the All Electronics
>catalog at the capacitors.  I was looking for some things around .1-micro
>farad.  Now everything is listed in MFD. ... Micro is usually written with a
>greek `Mu'.

"MFD" means microfarad.  Millifarad capacitors are invariably written as
thousands-of-microfarads.  US habit is to use microfarads (uF or mfd) and
picofarads (pF); Europeans also tend to use nanofarads (nF) (comfortably
nestled in between uF and pF); IC designers also worry about femtoFarads...

>In case anyone is wondering, I decided the best resolution to this quandary
>was to order stuff from Newark instead.
>DY ;-)

That's a lot extra to pay for a good typesetter...	:-)
How much do they charge for a megafarad capacitor, BTW?