Electronic color code

The electronic color code is used to indicate the values or ratings of electronic components, very commonly for resistors, but also for capacitors, inductors, and others. A separate code, the 25-pair color code, is used to identify wires in some telecommunications cables.

The electronic color code was developed in the early 1920s by the Radio Manufacturers Association (now part of Electronic Industries Alliance[1] (EIA)), and was published as EIA-RS-279. The current international standard is IEC 60062.[2]

Colorbands were commonly used (especially on resistors) because they were easily printed on tiny components, decreasing construction costs. However, there were drawbacks, especially for color blind people. Overheating of a component, or dirt accumulation, may make it impossible to distinguish brown from red from orange. Advances in printing technology have made printed numbers practical for small components, which are often found in modern electronics.

Contents

Resistor, capacitor and inductor

It is sometimes not obvious whether a color coded component is a resistor, capacitor, or inductor, and this may be deduced by knowledge of its circuit function, physical shape or by measurement. Resistor values are always coded in ohms (symbol Ω), capacitors in picofarads (pF), and inductors in microhenries (µH).

One decade of the preferred E12 values (there are twelve preferred values per decade of values) shown with their electronic color codes on resistors.
A 100 kΩ, 5% through-hole resistor.
A 0Ω resistor, marked with a single black band.

A diagram of a resistor, with four color bands A, B, C, D from left to right A diagram of a 2.7 MΩ color-coded resistor.
To distinguish left from right there is a gap between the C and D bands.

  • band A is first significant figure of component value (left side)
  • band B is the second significant figure
  • band C is the decimal multiplier
  • band D if present, indicates tolerance of value in percent (no color means 20%)

For example, a resistor with bands of yellow, violet, red, and gold will have first digit 4 (yellow in table below), second digit 7 (violet), followed by 2 (red) zeros: 4,700 ohms. Gold signifies that the tolerance is ±5%, so the real resistance could lie anywhere between 4,465 and 4,935 ohms.

Resistors manufactured for military use may also include a fifth band which indicates component failure rate (reliability); refer to MIL-HDBK-199 for further details.

Tight tolerance resistors may have three bands for significant figures rather than two, and/or an additional band indicating temperature coefficient, in units of ppm/K.

All coded components will have at least two value bands and a multiplier; other bands are optional (italicised below).

The standard color code per EN 60062:2005 is as follows:

Color Significant
figures
Multiplier Tolerance Temp. Coefficient (ppm/K)
Black 0 ×100 250 U
Brown 1 ×101 ±1% F 100 S
Red 2 ×102 ±2% G 50 R
Orange 3 ×103 15 P
Yellow 4 ×104 25 Q
Green 5 ×105 ±0.5% D 20 Z
Blue 6 ×106 ±0.25% C 10 Z
Violet 7 ×107 ±0.1% B 5 M
Gray 8 ×108 ±0.05% A 1 K
White 9 ×109
Gold ×10-1 ±5% J
Silver ×10-2 ±10% K
None ±20% M
 
  1. Any temperature coefficent not assigned its own letter shall be marked "Z", and the coefficient found in other documentation.
  2. For more information, see EN 60062.

A resistor which (read left to right) displays the colors yellow, violet, yellow, brown. The first two bands represent the digits '4, 7. The third band, another yellow, gives the multiplier 104. The value is then 47 x 104 Ω, or 470 kΩ. The brown band is a s then a tolerance of ±1%.

Resistors use Preferred numbers for their specific values, which are determined by their tolerance. These values repeat for every decade of magnitude; 6.8, 68, 680, and so forth.

Zero ohm resistors are made as lengths of wire wrapped in a resistor-shaped body which can be substituted for another resistor value in automatic insertion equipment. They are marked with a single black band.[3]

The 'body-end-dot' or 'body-tip-spot' system was used for radial-lead composition resistors sometimes found in vacuum-tube equipment; the first band was given by the body color, the second band by the color of the end of the resistor, and the multiplier by a dot or band around the middle of the resistor. The other end of the resistor was colored gold or silver to give the tolerance, otherwise it was 20%.[4]

Extra bands on ceramic capacitors will identify the voltage rating class and temperature coefficient characteristics.[4] A broad black band was applied to some tubular paper capacitors to indicate the end that had the outer electrode; this allowed this end to be connected to chassis ground to provide some shielding against hum and noise pickup.

Polyester film and "gum drop" tantalum electrolytic capacitors are also color coded to give the value, working voltage and tolerance.

Mnemonics

A useful mnemonic matches the first letter of the color code, by order of increasing magnitude. There are many variations:

  • Bad boys rape our young girls but Violet gives willingly.[5]

The tolerance codes, gold, silver, and none, are not usually included in the mnemonics; one extension that includes them is:

  • Bad beer rots our young guts but vodka goes well – get some now.[6]

The colors are sorted in the order of the visible light spectrum: red (2), orange (3), yellow (4), green (5), blue (6), violet (7). Black (0) has no energy, brown (1) has a little more, white (9) has everything and grey (8) is like white, but less intense.[7]

Examples

Color coded resistors

From top to bottom:

  • Green-Blue-Brown-Brown
    • 560 ohms ± 1%
  • Red-Red-Orange-Gold
    • 22,000 ohms ± 5%
  • Yellow-Violet-Brown-Gold
    • 470 ohms ± 5%
  • Blue-Gray-Black-Silver
    • 68 ohms ± 10%

The physical size of a resistor is indicative of the power it can dissipate, not of its resistance.

Printed numbers

0Ω and 27Ω (27×100) surface-mount resistors.

Color-coding of this form is becoming rarer. In newer equipment, most passive components come in surface mount packages. Many of these packages are unlabeled and, those that are, normally use alphanumeric codes, not colors.

In one popular marking method, the manufacturer prints 3 digits on components: 2 value digits followed by the power of ten multiplier. Thus the value of a resistor marked 472 is 4,700 Ω, a capacitor marked 104 is 100 nF (10x104 pF), and an inductor marked 475 is 4.7 H (4,700,000 µH). This can be confusing; a resistor marked 270 might seem to be a 270 Ω unit, when the value is actually 27 Ω (27×100). A similar method is used to code precision surface mount resistors by using a 4-digit code which has 3 significant figures and a power of ten multiplier. Using the same example as above, 4701 would represent a 470x101=4700 Ω, 1% resistor. Another way is to use the "kilo-" or "mega-" prefixes in place of the decimal point:

1K2 = 1.2 kΩ = 1,200 Ω
M47 = 0.47 MΩ = 470,000 Ω
68R = 68 Ω

For some 1% resistors, a three-digit alphanumeric code is used, which is not obviously related to the value but can be derived from a table of 1% values. For instance, a resistor marked 68C is 499(68) × 100(C) = 49,900 Ω. In this case the value 499 is the 68th entry of a table of 1% values between 100 and 999.

References

  1. ^ EIA
  2. ^ IEC 60062 Title: "Marking codes for resistors and capacitors" (IEC Webstore)
  3. ^ NIC Components Corp. NZO series zero-ohm resistors.
  4. ^ a b Reference Data for Radio Engineers, Federal Telephone and Radio Corporation, 2nd edition, 1946 page 52
  5. ^ Booker, M. Keith (1993). Literature and Domination: Sex, Knowledge, and Power in Modern Fiction. University Press of Florida. ISBN 0813011957. http://books.google.com/books?id=EEt6pm0e5IAC&pg=PA105&ots=5WFzofxqUq&dq=%22bad+boys+rape+our+young+girls%22&sig=njfuNiBbH8FsQ6frNNPJQPenTs4.
  6. ^ The Mnemonics Page - Dean Campbell, Bradley University Chemistry Department
  7. ^ Preston R. Clement and Walter Curtis Johnson (1960). Electrical Engineering Science. McGraw-Hill. p. 115. http://books.google.com/books?id=4tkiAAAAMAAJ&q=resistor+color-code+spectrum+energy&dq=resistor+color-code+spectrum+energy&lr=&as_drrb_is=q&as_minm_is=0&as_miny_is=&as_maxm_is=0&as_maxy_is=&as_brr=0&ei=P8ZfSoSWIYSYkgTWv_zwCg.

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