# Why strange 0.047 uF value of caps

Discussion in 'Electronic Basics' started by Ignoramus20083, May 14, 2007.

1. ### Ignoramus20083Guest

Why are so many caps spec'ed as 0.047 uF or multiples thereof, thanks

2. ### John PopelishGuest

Capacitors and resistors (and usually inductors) are made
with "strange" nominal values that are equally far from each
other on a percentage basis. A .047 uF 10% tolerance cap
can vary between .047/1.1 and .047*1.1 or .043 and .52 uF.
The next lower 10% value would be a .039 uF, since it can
vary anywhere between .35 and .043 uF. The next higher 10%
value is .056 uF since it can be between .051 and .062 uF.

Here is a table of all the standard values for various
tolerances:
http://www.logwell.com/tech/components/resistor_values.html

3. ### Homer J SimpsonGuest

They aren't. .047 is an E24 series number.

4. ### EeyoreGuest

It's because component values are oganised (roughly) as percentage increases
compared to the next value with 6,12, 24, 48 or 96 increments in a decade (
known as E6 values, E12 etc... ).

so the E6 values run for example

1, 1.5, 2.2, 3.3, 4.7, 6.8 (where each value is about 1.5 times the
previous one)
10, 15........

5. ### ChrisGuest

And these overlap for different tolerances. So, if you needed only
20% tolerance:

1 = 0.8 to 1.2
1.5 = 1.2 to 1.8
2.2 = 1.76 to 2.66
3.3 = 2.64 to 3.96
4.7 = 3.76 to 5.64
6.8 = 5.44 to 8.16
10 = 8 to 12

and so on. The E12s overlap at 10% tolerance, and the E24s overlap at
5%. Caps tend to be specified at 20% tolerance, which makes 4.7 a
very common value.

Cheers
Chris

8. ### MarraGuest

Yes you can by adding components in series or parallel !

Where do you think the values come from !

10. ### MarraGuest

Yes and I am becoming intolerant of you !

12. ### neon

1,325
0
Oct 21, 2006
values for all things comes not from the manufacture whims but rather from another source US goverment and since they are the big users of these things we are stuck with them.