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 Identifying Caps
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 Return to top of page · Post #: 1 · Written at 12:00:39 AM on 26 January 2017.
Tallar Carl's avatar
 Location: Latham, ACT
 Member since 21 February 2015
 Member #: 1705
 Postcount: 1619

This may seem silly to some of you but I have a lot of caps I will be selling at various meets. The number of zeros at the front of the value represents what?. I mean .0 is what pico or nano can anyone help me with this.

 Return to top of page · Post #: 2 · Written at 12:19:34 AM on 26 January 2017.
Robbbert's avatar
 Location: Hill Top, NSW
 Member since 18 September 2015
 Member #: 1801
 Postcount: 1484

1000pF = 1nF
1000nF = 1μF

.001 is 0.001μF (= 1nF)

4700 is 4700pF

.05 is 0.05μF (= 50nF)

 Return to top of page · Post #: 3 · Written at 10:26:40 PM on 4 February 2017.
Little Nipper's Gravatar
 Location: Australia, SA
 Member since 21 December 2011
 Member #: 1047
 Postcount: 85

Search for 'Engineering Notation', for an explanation of the zero's.


Search for 'Capacitor Codes' for an explanation of markings.

The Unit Of Charge is the farad, which is way too large for electronics, so we use a million times less number, micro-Farads or μF to express the value of larger capacitors, like electrolytic and tantalums. Timing circuits and faster circuits need values less than 1μF so these plastic capacitors used to be labeled 0.XXXμF and so on, but recently they are labeling them in nano Farads just to confuse us all. (One Thousand Million times less than a Farad) Radio frequency requires very small values of capacitance, which include ceramic capacitors which are labeled in pico Farads, a million, million times less or a billion times less than a Farad.

Now you can see the type of capacitor and maybe it's relative size can give you a clue to it being pF or μF.

Then there are the capacitor codes from different parts of the world, which sometimes show you the significant numbers and a multiplier, but I am sure you have just read about these.

Most circuit diagrams have a note which says something like "All capacitors expressed in xF unless otherwise stated", so the diagram is less cluttered and clearer.

But it is still too easy to make a mistake, the best idea is to check them with a capacitance meter. I check the old ones after removal too.

Hope this helps.

 Return to top of page · Post #: 4 · Written at 10:39:05 PM on 4 February 2017.
Brad's avatar
 Location: Greenwich, NSW
 Member since 15 November 2005
 Member #: 1
 Postcount: 6573

Generally, all electrolytic capacitors are large enough to be measured in μF (or mfd in the old way of expressing the unit of capacitance) and most other capacitors of any sort usually get shown in pF or nF to reduce the number of noughts in the value.

μ is a Greek letter and is pronounced m-you and is the SI symbol for a millionth of a unit. As an added bonus, it is easier to type here than on any other forum - typing a lowercase U and a capital F will cause the forum software to render it as μF rather than uF.

(in most cases anyway)

A valve a day keeps the transistor away...

 Return to top of page · Post #: 5 · Written at 1:20:53 PM on 5 February 2017.
Little Nipper's Gravatar
 Location: Australia, SA
 Member since 21 December 2011
 Member #: 1047
 Postcount: 85

Great idea for the software Brad, I thought I was sprung being lazy and using little u and capital F. I was tired and did not feel like finding Character Map.

If anyone needs to know, 'Character Map' is where you go in Windows for a list of all the characters and symbols. Just click the one you want, click copy, and paste it where you want.

All Programs/Accessories/System Tools/Character Map, for Windows 7.

Æ ¼ ½ ¾ Ω μ ²

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