help, uf = nf = pf

got me self all confudled orderin some silver mica caps.

is this right -

1nf = 1000pf

47nf = 47,000nf

 

1 milli Farad (1mF) = 1000 micro Farads (1000uF)*
1 micro Farad (1uF)* = 1000 nano Farads (1000nF)
1 nano Farad (1nF) = 1000 pico Farads (1000pF)
1 pico Farad (1pF) = 1000 femto Farads (1000fF)
1 femto Farad (1fF) = 1000 ato Farads (1000aF)

*micro should REALLY be signified with a greek mu, but it's often unavailable in symbol sets, and in those situations is generally substituted with a u

 

Try this

pico-farad nano-farad micro-farad
(pF) (nF) (mF,uF or mfd)
1000 1 or 1n 0.001
1500 1.5 or 1n5 0.0015
2200 2.2 or 2n2 0.0022
3300 3.3 or 3n3 0.0033
4700 4.7 or 4n7 0.0047
6800 6.8 or 6n8 0.0068
10000 10 or 10n 0.01

etc......

 

oook

so that means i got it right, i think

 

Just a comment on Lee's answer (not pointing fingers, but just in case anyone is confused), mF is NOT used for micro-Farad. It signifies milliFarad, which is an order of magnitude larger. In practice, a capacitor rated in milliFarads is a very rare thing (a Farad is an enormous unit), and usually we will use thousands or tens of thousands of micro-Farads.

Also, in case anyone is interested or gets confused, electronic engineers use all sorts of strange words to refer to cap values:

microFarad: "oufff" (phonetic pronounciation of uF), "mike" eg "Four-seventy ouff".
nanoFarad: "nan", eg "Hundred nan"
picoFarad: "puff" eg "Thirty-three puff"

 

...and 50 pints of Cobra please

Why are the standard cap values what they are - why the hell does 47 crop up so often???

Michael.

 

Michael, I found the following explanation for why capacitor values seem so 'weird'. Hope it helps.

Real capacitor values (the E3 and E6 series)

You may have noticed that capacitors are not available with every possible value, for example 22µF and 47µF are readily available, but 25µF and 50µF are not!

Why is this? Imagine that you decided to make capacitors every 10µF giving 10, 20, 30, 40, 50 and so on. That seems fine, but what happens when you reach 1000? It would be pointless to make 1000, 1010, 1020, 1030 and so on because for these values 10 is a very small difference, too small to be noticeable in most circuits and capacitors cannot be made with that accuracy.

To produce a sensible range of capacitor values you need to increase the size of the 'step' as the value increases. The standard capacitor values are based on this idea and they form a series which follows the same pattern for every multiple of ten.

The E3 series (3 values for each multiple of ten)
10, 22, 47, ... then it continues 100, 220, 470, 1000, 2200, 4700, 10000 etc.
Notice how the step size increases as the value increases (values roughly double each time).

The E6 series (6 values for each multiple of ten)
10, 15, 22, 33, 47, 68, ... then it continues 100, 150, 220, 330, 470, 680, 1000 etc.
Notice how this is the E3 series with an extra value in the gaps.

The E3 series is the one most frequently used for capacitors because many types cannot be made with very accurate values.

 

Penance,
There a neat little convertor thingy about halfway down this page, Pico, nano, milli, convertor

 

cheers S&C

 

To expand on BL21DE3's correct answer, it's a matter of tolerance.

Look at resistor values in the E12 series with a 10% tolerance. The E12 values are 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68 and 82.

With that tolerance, we can have a 10 ohm resistor with a resistance of 11 ohms. We can also have a 12 ohm resistor with a value of 10.8 ohms. No point having a value between. This still works at the top, with a nominal 68 ohm resistor having a value of 74.8 ohms and a nominal 82 ohm with a value of 73.8 ohms.

Capacitors are rather less easy to make accurate than resistors, and are often only available in 20% tolerances (almost all electrolytics are 20%).

As BL21DE3 said, E6 is E3 with some gaps filled in. E12 is the same again, and E24 the same again.

 

Oh for the joys of a 2 puff cap

 

:JPS: