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It’s difficult to print resistance values on resistors because they’re usually so small. As a result, colour bars representing electrical resistance are printed on them. Resistor colour code refers to these colour bands. The Radio Manufacturers Association invented the resistor colour code in the 1920s (RMA).
Resistor colour code meaning
Resistor colour coding employs coloured bands to instantly identify the resistor’s resistive value and tolerance percentage, as well as the physical size of the resistor, indicating its wattage rating.
When the body of the resistor is large enough to show the print, as with large power resistors, the resistance value, tolerance, and wattage rating are usually displayed as numbers or letters on the resistor’s.
Colour | Digit | Multiplier | Tolerance |
Black | 0 | 1 | |
Brown | 1 | 10 | ±1% |
Red | 2 | 100 | ±2% |
Orange | 3 | 1000 | |
Yellow | 4 | 10000 | |
Green | 5 | 100000 | ±0.5% |
Blue | 6 | 1000000 | ±0.25% |
Violet | 7 | 10000000 | ± 0.1% |
Grey | 8 | ± 0.05% | |
White | 9 | ||
gold | 0.1 | ± 5% | |
Silver | 0.01 | ± 10% |
For their precise values, resistors use the E series of preferred numbers, which are defined by their tolerance. For every tenth of a magnitude, these values repeat:… 0.68, 6.8, 68, 680,… The E6 series, with six values: 10, 15, 22, 33, 47, 68, then 100, 150,…, is used for resistors with a 20 percent tolerance; each number equals essentially the preceding value multiplied by 610. The E12 series, with 1210 as multiplier, is used for resistors with a 10% tolerance; comparable schemes, up to E192, are used for resistors with a 0.5 percent or tighter tolerance. The tolerance is proportional to the gap between the values, thus neighbouring values at the extremes of tolerance almost just overlap; for example, 10 + 20% equals 12 in the E6 series, and 15 + 20% equals 12 as well.
Zero ohm resistors are lengths of wire wrapped in a resistor-like body that may be installed on a printed-circuit board (PCB) by automatic component-insertion equipment. They are identified with a single black band. On PCBs, they’re usually utilised as insulating “bridges” where two tracks would otherwise cross, or as soldered-in jumper wires for configuring the board.
Body-end-dot system
For cylindrical composition resistors (built before WWII), the “body-end-dot” or “body-tip-spot” system was used; the first band was determined by the body colour, the second band by the colour of one end of the resistor, and the multiplier was determined by a dot or band around the middle of the resistor. The resistor’s opposite end was in the body colour, silver, or gold for tolerances of 20%, 10%, and 5%, respectively (tighter tolerances were not routinely used).
How to read resistor colour code
Hold the resistor such that the tolerance band is on your right when reading them. The tolerance band is usually gold or silver in colour and is set apart from the other bands by a few millimetres.
Begin by noting all of the colour of the bands on your left and writing them down in order.
Then, using the table below, figure out which digits they represent.
The multiplier band is located adjacent to the tolerance band. The value given is 102 if the colour of this band is Red (representing 2).
Resistor colour code mnemonic
The following mnemonic can help you recall the colour code values:
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The first letters of the colours are represented by capital letters, and their locations are represented by digit values. Now that we know how to calculate the resistance value of a resistor. In the next section, we’ll solve various challenges relating to this.
Conclusion
Resistor colour coding employs coloured bands to instantly identify a resistor’s resistive value and tolerance percentage, with the resistor’s physical size indicating its wattage rating.
When the body of the resistor is large enough to show the print, as with large power resistors, the resistance value, tolerance, and wattage rating are usually displayed as numbers or letters on the resistor’s body.
