Capacitance of a capacitor is the ability of a capacitor to store maximum charge on its plates. The capacitance of a capacitor is measured in the units of Farads. Generally the capacitance values, working voltage and tolerance values are indicated on the body of a capacitor.
But sometimes it is difficult to identify these capacitance and voltage values on the capacitor body in the case of decimal values. It also causes misreading of the actual capacitance and voltage values. So, a technique was used to identify the capacitance values by using the letters like p (pico) and n (nano) instead of decimal values (such as200k=200*1000pF=200nF and 47n=47nF, n47=0.47nF etc).
So to avoid these problems a color scheme was introduced for capacitors like resistors. This colour scheme for capacitors is usually called as capacitor color coding. In this scheme each color of a capacitor indicates a specific capacitance value. Using this color scheme we can easily identify the capacitance values, voltages and tolerance values of any capacitor. These color schemes; color coding and colors assigned for values are explained in below.
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The capacitor has the capacitance value, voltage , tolerance and manufacturer numbers on the body of a capacitor. Some voltage values are used as references for working voltages of a capacitor. In this representation we see some letters or characters like J, K, N, M etc. Now let us the meaning of those letters which are used on the body of a capacitor.
J-Type => Dipped Tantalum type capacitors
K-Type => Mica type capacitors
L-Type => Polyester (or) Polystyrene type capacitors
M-Type => Electrolytic 4 Band type capacitors
N-Type => Electrolytic 3 Band type capacitors
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Image Resource Link: www.electronics-tutorials.ws/capacitor/cap29zz.gif
The capacitors which are shown in the above figure are metalized polyester capacitors with color codes. In this each color represents a specific parameter for capacitance values, tolerance and working voltages. All the above capacitors have different capacitance and tolerance values. These values can be understood by the color code table which is given at the side of capacitors in the above figure.
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Image Resource Link: www.electronics-tutorials.ws/capacitor/cap29a.gif
The above figure shows the Disc and Ceramic capacitors with color codes. These colour codes are used from many years for non-polarized capacitors like disc and ceramic capacitors. But it is difficult to identify the values in the case of old capacitors. So these old capacitors are now replaced with new numbers.
In three digit number representation , the third number represents number of zeros, such as 471=470pF, 101=100pF. In the case of two digit number representation tolerance is also identified. In two number representation disc or film capacitors have the capacitance value usually in pico-Farads, for example 47=47pF, 20=20pF. In the above figure we observed the capacitance values and tolerance for small disc or large disc capacitors can be calculated by using color code which is shown at the side of capacitors.
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Capacitor has numbers and letters on its body to identify the capacitance values and tolerance values respectively. Letters for the specific tolerance value representation is shown in the below table. Now we will see one example to understand this concept below.
The capacitor which is shown in the above figure has 473J code on its body. Here 4 is first digit, 7 is second digit and 3 is the number of zeros i.e. the capacitance value is 47*1000pF=47000pF=47nF=0.047uF. Here letter ‘J’ denotes the tolerance of a capacitor, referring to above table, tolerance of this capacitor is +/-5%. In this way by just using numbers and letters on the body of a capacitor, we can easily determine the capacitance values and tolerances of capacitors.
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The capacitance values of capacitor are measured in pico-Farads, nano-Farads, or micro-Farads. The relation between these values for different letter codes is shown in the above table. From this table we clearly can understand about the units of capacitance. The basic relation between them is 1uF=1000nf=1000000pF.
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In the previous tutorials, we have seen what is capacitance and charge?. In this tutorial we are going to learn how to read the capacitor value?. For some applications, it is necessary to know the tolerance and voltage values of the capacitor along with the capacitance. All these parameters are represented on the body of the capacitor.
Different types of capacitors have different ways of representing the capacitance values . Capacitors like electrolytic capacitors, non- polarised capacitors, large ac oil filled paper capacitors have capacitance and voltage, tolerance values written on its body using numbers and letters.Some capacitors have values represented using color code. Let us see how to read capacitance value in these two methods.
How to read capacitor value written on capacitors??
Let us see how to read the capacitor values with numbers and alphabets. Along with the capacitance other values like tolerance and voltage were written on the capacitor itself if there is enough space. But for small capacitors like ceramic capacitors , as the space is not enough , capacitor values are represented using shorthand notation.
Reading capacitor values on Large capacitor(cylindrical capacitors)
For large capacitors, generally capacitor value is written on the side of the capacitor.
- The above figure shows a 22 micro farad capacitor .Capacitance value is expressed in Farads (F or FD).
- Here are the units used for representing capacitor value .Micro farad (uf,µf,mF (or) MF) , Nano farad ( nF ), Pico farad(pF).
- Voltage rating on the capacitor indicates the maximum value voltage that capacitor can handle.Voltage rating on the capacitor is indicated by V, VDC, and VDCW.
- VAC represents that capacitor is designed for AC circuit.
- It is to be noted that DC rating capacitors should not be used for AC unless you have proper knowledge to use that capacitor. Some capacitors have voltages represented in codes instead of value.
- Tolerance value is indicated using % symbol before the number. Tolerance value represents the variation of capacitance value .
Reading the values of small capacitors(ceramic capacitors)
Ceramic capacitors have very small area to print the value of capacitance. So capacitance on these capacitors is represented using short hand notation. Let us see how to calculate these values. Generally capacitance of ceramic, tantalum ,film capacitors is expressed in Pico Farad.
Step 1: If the capacitor has two numerical values.
- If the notation on the capacitor has 2 digits and a letter (like 22M) ,then it has capacitance value of 22.
Some capacitors have letters in the second position and numerical value in first position.
Ex: 5R2 = 5.2PF.
- In place of R if the letters like p, n, u are present then they represent units of capacitance.
Ex: 4n1 = 4.1nF, p45=0.45pF
- Capacitor shown above has notation 104 on it.
- Capacitance is calculated as 10x 104 = 105pf = 0.1uf
- If the third digit is between 0 to 6 follow the above procedure.
- If it is 8 multiply it by using 0.01.for example 158 =15×0.01 = 0.15pF
- If it is 9 multiply it by using 0.1.For example 159 =15×0.1 =1.5pF
The tolerance value for these capacitors is represented using single letter.Each letter has a value.
|P||–0%, + 100%|
|S||–20%, + 50%|
|W||–0%, + 200%|
|X||–20%, + 40%|
|Z||–20%, + 80%|
Capacitance value Calculator
- Color coding of capacitors is an age old technique. But some of these capacitors are still in use today. So let us see how to calculate the value of capacitance and voltage rating if they are represented using color coding.
- Generally color codes are indicated using Dots or Bands. For Mica capacitors color coding is shown in Dots while for tubular capacitors it may be shown using bands. The number of dots or bands on a capacitor may vary from one another .
Below two tables shows the values of colors given on the capacitors.
Capacitance Color Code Table
|Color||A||B||D||(T) > 10pf||(T) < 10pf|
Capacitor Voltage Color Code
Let us see an example of ceramic or disc capacitor for calculating the color code on it.
Disc & Ceramic Capacitor
These colour codes are used from many years for non-polarized capacitors like disc and ceramic capacitors. But it is difficult to identify the values in the case of old capacitors. So these old capacitors are now replaced with new numbers.