Friday, January 13, 2012

How to get capacitor value with capacitor coding

Let see how to decode the capacitor, to get the value of the capacitance

Unpolarised capacitors (small values, up to 1µF)

Examples:   small value capacitors    Circuit symbol:   capacitor symbol Small value capacitors are unpolarised and may be connected either way round. They are not damaged by heat when soldering, except for one unusual type (polystyrene). They have high voltage ratings of at least 50V, usually 250V or so. It can be difficult to find the values of these small capacitors because there are many types of them and several different labelling systems!
100nF capacitor Many small value capacitors have their value printed but without a multiplier, so you need to use experience to work out what the multiplier should be!
For example 0.1 means 0.1µF = 100nF.
Sometimes the multiplier is used in place of the decimal point:
For example:   4n7 means 4.7nF.

Capacitor Number Code

A number code is often used on small capacitors where printing is difficult: 1nF capacitor
  • the 1st number is the 1st digit,
  • the 2nd number is the 2nd digit,
  • the 3rd number is the number of zeros to give the capacitance in pF.
  • Ignore any letters - they just indicate tolerance and voltage rating.
For example:   102   means 1000pF = 1nF   (not 102pF!) For example:   472J means 4700pF = 4.7nF (J means 5% tolerance).

Colour Code
ColourNumber
Black
0
Brown
1
Red
2
Orange
3
Yellow
4
Green
5
Blue
6
Violet
7
Grey
8
White
9

Capacitor Colour Code

A colour code was used on polyester capacitors for many years. It is now obsolete, but of course there are many still around. The colours should be read like the resistor code, the top three colour bands giving the value in pF. Ignore the 4th band (tolerance) and 5th band (voltage rating). 10nF and 220nF capacitors For example:
    brown, black, orange   means 10000pF = 10nF = 0.01µF.


Note that there are no gaps between the colour bands, so 2 identical bands actually appear as a wide band.
For example:
    wide red, yellow   means 220nF = 0.22µF.


Polystyrene Capacitors

polystyrene capacitor This type is rarely used now. Their value (in pF) is normally printed without units. Polystyrene capacitors can be damaged by heat when soldering (it melts the polystyrene!) so you should use a heat sink (such as a crocodile clip). Clip the heat sink to the lead between the capacitor and the joint.

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