In every schematic you can find few capacitors. Sometimes you remove old caps from some junk boards. And sometimes it is difficult to determine the cap value. There is some standards for cap coding, but not every manufacturer take care about it. The capacitance is measured in farads. But one farad is very big value, so people use fractional parts of it. These parts are decimal and called using old names:mili (m, *10
-3), micro (Î¼, u, *10
-6), nano (n, *10
-9), piko (p, *10
I have difficulties translating nanofarads to piko or microfarads. So I am using this picture. It helps me. Just imagine you cap value written on the picture and you can read the value in other form:
Standard says, that there are only two digits on the capacitor body, the value is expressed in pikofarads (47 = 47pF), if numbers are three the first two number show value and last is representing multiplication value, or just how many zeros you must add (472 = 4700pF). But in real world …
Just look at the scans:
In the first row you can see SMD tantalum caps. They never be in pikofarads 🙂 , so two digit caps is in microfarads. Sometimes manufacturer print Greek letter mju – Î¼, to show that it is microfarads. On the second row there is another curiosity- the value of small cap is printed in mikrofarads- .0033, the leading zero is omitted. I think is is old matsushita or victor company in Japan cap.
Here is that tantalum with Î¼ and other standard caps.
And here is old “European”, I think Siemens made capacitors. The “n” shows that value are in nanofarads. On far right the cap is without letter- value is in pikofarads.
On the top row is special capacitor for protection. One side is full of various certificates, while on other you can see very small print of value. On the bottom there is two identical caps made by different Chinese manufacturers.
And the best thing is, that always use multimeter to measure the value of the caps. Especially if you are playing with SMD ones.