Thursday, March 6, 2014

How to read value of a Capacitor ?

Capacitance is the ability to store electrons and is measured in Farads.One Farad is a very large value! So most capacitors used in electronic circuits  are measured in MicroFarads (uF) or even Picofarads (pF).

Capacitance = Q / V
Where Q is the charge and V is the voltage.
Thus the capacitance is the charge divided by voltage.

The important parameters of the capacitor are
1. Value-Value is marked on the capacitor directly or in colour codes
2. Tolerance-It indicates how much more or less the actual capacitance of the capacitor
3. Working voltage-It is the maximum voltage a capacitor can withstand before the dielectric breakdown
4. Leakage current.There is always small leakage current in all capacitors. Ideally this should be zero. But no capacitor is perfect without leakage current. Tantalum capacitor is comparatively better with minimum leakage current

 Value
1pf (Pico Farad)    = 0.001nf (Nano Farad)
1nf (Nano Farad)   = 0.001μf (Micro Farad)
1μf (Micro farad) = 0.001mf (Milli farad)
1mf (Milli farad)  = 0.001F (Farad)

Small disc Capacitor having two digits shows its actual value in pf ( picofarad)


Value of this capacitor is 22pf





capacitor may have 3 or 4 digits at its body.The last digits is the number tells number of zeros added to the prefix number
 Value of this capacitor is 15* 0000 (4 zeros)
=150000 pf =150n =0.15μf


Tollerence
 The alphabet marking at the end of capacitor value shows its tolerance. (underlined letter in the shown image).
 B as  ±0.10%
 C as  ±0.25%
 D as ±0.5%
 E as  ± 0.5% This is a duplication of a D code
 F as ±1%
 G as ± 2%
 H as ± 3%
 J  as ±5%
 K as ±10%
 M as ± 20%
 N as ± 0.05% 
 P as  +100% to -0 %
 Z as +80% to -20 % 
Voltage rating 
voltage rating of a capacitor is Normally found below the value. In electrolytic capacitor it is shown next to the value markings
Voltage Rating of Various type capacitors 


Ceramic
16V,25V,50V,100V,600V,1000V
Electrolytic
10V,16V,25V,35V,50V,63V,100V,160V,250V,350V,450V
Tantalum
10V,16V,20V,25V,35V,50V
Mylar Polyester
50V,100V,200V,400V
Mylar Metal
250V,400V,630V.
Maximum operating voltage also indicated alphabet coding
1H =50V
2A=100V
2T =150V
2D = 200V
2E = 250V
2G = 400V
2J =630V
Common Temperature Coefficient Characteristics (Ceramic)

Temperature Coefficient
Operating Temperature Range
Capacitance Change
Minimum Capacitor Tolerance
Y5E
-30°C ~ +85°C
± 4.7%
±10%
Y5F
-30°C ~ +85°C
±7.5%
±20%
Y5P
-30°C ~ +85°C
± 10%
±10%
Y5U
-30°C ~ +85°C
+22% / -56%
±20%
Y5V
-30°C ~ +85°C
+22% / -82%
±20%
Z5U
+10°C ~ +85°C
+ 22% / -56%
±20%
Z5V
+10°C ~ +85°C
+ 22% / -82%
+80% / -20%

Polarity
Electrolytic and Tantalum capacitor Shows polarity markings  






Colour coding
 some capacitors are colour coded to indicate value, tolerance, working voltage etc. These colour bands are numbered from the top of the capacitor to the base. The colour coding is similar to Resistor colour coding.
First band – First number of colour code chart
Second band – Second number of colour code chart
Third band – Number of Zeros
Fourth band – Tolerance (Black 20%, White 10 % and Green 5 %)
Fifth band – Appears as body colour. Working voltage (Red 250V, Yellow 400 V)

 0   2   3    4    5   6   7   8 

Dielectric material
The dielectric material is sometimes designated by another code: (note: the materials in the table below are not ceramic capacitors as implied, but plastic and paper)
Marking Material
KT Polyester Film / Foil
MKT Metallized Polyester (PETP)
KC Polycarbonate Film / Foil
MKC Metallized Polycarbonate
KS Polystyrene Film / Foil
KPS foil/pps?
MPS Metallized pps
KP Polypropylene Film / Foil
MKP Metallized Polypropylene
MP Metallized paper
Please note that the table above is valid most of the time but not always because it is not a real standard. To be real sure you may check the data sheet from the manufacturer in mind.
The cap color can also indicate the dielectric:
Black Brown Red Orange Yellow Green Blue Violet Red/Orange Orange/Orange Yellow/Orange Green/Orange Blue/Orange Red/Violet C0G/NP0 N030 N080 N150 N220 N330 N470 N750 N1000 N1500 N2200 N3300 N4700 P100

2 comments:

  1. SMD electrolytic capacitors are often marked with their capacitance and working voltage, e.g. 10 6V is 10 µF 6V . Sometimes a code is used instead, which normally consists of a letter and 3 digits. The letter indicates the working voltage and the 3 digits (2 digits and multiplier) give the capacitance in pF.


    Letter Voltage
    e 2.5
    G 4
    J 6.3
    A 10
    C 16
    D 20
    E 25
    V 35
    H 50

    The band or stripe indicates the positive terminal.

    For example, a capacitor marked A475 is a 4.7m F 10V unit.

    475 = 47 x 105 pF = 4.7 x 106 pF = 4.7m F

    ReplyDelete
  2. SMD ceramic capacitors are sometimes marked with a code, consisting of one or two letters and a digit. The first letter if present is a manufacturer code (i.e K for Kemet, etc.), the second letter the mantissa and the digit the exponent (multiplier) of the capacitance in pF. For example S3 is a 4.7nF (4.7 x 10³ pf) capactitor from an unknown manufacturer, while KA2 is a 100 pF (1.0 x 10² pF) capacitor from Kemet.
    Letter / Mantissa
    A 1.0
    B 1.1
    C 1.2
    D 1.3
    E 1.5
    F 1.6
    G 1.8
    H 2.0
    J 2.2
    K 2.4
    L 2.7
    M 3.0
    N 3.3
    P 3.6
    Q 3.9
    R 4.3
    S 4.7
    T 5.1
    U 5.6
    V 6.2
    W 6.8
    X 7.5
    Y 8.2
    Z 9.1
    a 2.5
    b 3.5
    d 4.0
    e 4.5
    f 5.0
    m 6.0
    n 7.0
    t 8.0
    y 9.0

    ReplyDelete