why 4.7uf and not 5uf?


Hi guys,
A curious question someone here might be able to answer...
why is that there is are 4.7uf or 2.2uf or 1.6uf etc values of capacitance
and not rounded values of say 5uf, 2uf, etc?
why those values 47, 22, 16, etc....?? is there something special about
them??
love to hear an reason for using those figures.
Reply to
KD
Loading thread data ...
Google is your friend. Look for preferred values.
Reply to
T.T.
"KD"
** When 6 steps in value make up a decade ( ie 10 times) increase in value.
So each step needs to be the 6th root of 10.
10 exp 0.1666 = 1.468
The exact steps then are:
1, 1.47, 2.15, 3.16, 4.64, 6.81, 10.
Rounded to :
1, 1.5, 2.2, 3.3, 4.7, 6.8, 10.
For 12 steps, the number are:
1, 1.21, 1.47, 1.78, 2.15, 2.61, 3.16, 3.83, 4.64, 5.62, 6.81, 8.25, 10.
......... Phil
Reply to
Phil Allison
Phil,
Your knowledge amazes me!
Jackie
capacitance
value.
Reply to
Jackie
This is were the E6 and E12 range comes in
e.g. E6 range has 6 values per decade
Phil,
Your knowledge amazes me!
Jackie
capacitance
value.
Reply to
Frank
"Jackie"
** Yeah - so I can use a "scientific" pocket calculator.
BTW
Do YOU know what is the same as the 12th root of 2 ?
............. Phil
Reply to
Phil Allison
I'm sure this is a loaded question! - No I don't
Jackie
about
6.81,
Reply to
Jackie
Amazing!.. Thank you Phil!..
So why 6 steps in value value make up a decade? (Why 6?)
Reply to
Posun Hurla
"Posun Hurla"
** Think about tolerace percentages:
20 %, 10 % , 5 %, 2% etc.
6 steps makes good sense when the allowable tolerance is +/- 20 %.
.......... Phil
Reply to
Phil Allison
Maybe not, one answer I can think of is a semitone. A semitone is the difference in pitch between each fret on the guitar or practically any musical instument that is tuned to what is called a "chromatic scale" (aka equal tempered 12 note scale). Musical tones are measured in semitones and octaves where as electrical component values are normally measured in decades and as Phil pointed out.
regards, Johnny.
Reply to
Johnny
"Johnny" "Jackie"
** Spot on.
** That is the connection.
Eg: a " third octave" audio equaliser has steps that are governed by the 3rd root of 2.
......... Phil
Reply to
Phil Allison
when i was a lad,,,,,,,, 2.5uF 5uF 7.5uF was the go. with electro caps near enough is good enough anyway.
E3 are the most used values ie; 3 values per decade: 1, 2.2, 4.7, 10, 22, 47 etc
Reply to
Ed -|-

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.