[sdiy] more about ceramic disc caps

[harry]

This is not REALLY dumb... its sad actually.

There are several marking conventions. Most small caps will be in
Picofarads as a rule... but they can be labeled very differently

One way is with two digits and a multiplier...
so
100 = 1, 0, and no zeros = 10pf
101 = 1,0, and one zero = 100pf
102 = 1000pf
103 = 10,000pF or .01uF

The other way is just the value
10 = 10pf
56 = 56pF  (with only two digits you have no doubt)

If the 680 was made by the same manufacturer (maybe yes...maybe no)
it will be 680pF.

Some DVM can read capacitance... this can be handy in these cases.
you might also put the unknown cap in series with a known value you
think is close. Put a high frequency (might be VERY high) through them
and measure the AC voltage drop across the unknown.  The test frequency
has to be high enough that the wave does not distort. There are other test
methods.

Or buy ones that you know how they are marked...

H^)

Have you read the Field Guide to Capacitors yet at www.musicsynthesizer.com
and several other sites? The Z5U question is answered there  ;^P

John Lamb wrote:

> This is really dumb, but how do I read the values on ceramic disc caps?  I have a slew that are marked
> differently from anything I have seen before -- "56J" "680J" -- I understand the J is the tolerance rating, in
> this case 5% -- but is this 56 pf?  56 uf?  I'm confused on the units, I guess.
>
> Also I have some taht are marked "120GMV ; 1-3MEG ; L" and "0015M ; Z5F" -- I'm confused on units
> and just this general mess.  Any help is appreciated, and simply tolerating my insipid and amateur questions
> is appreciated, as well.  :)
>
> Thanks again
> John Lamb