Why are Resistances Color Coded?
A resistor is a device that has two terminals. It is essential for many electronic and control devices. The actual function of resistance is to obstruct the path of current and limit it. In other words, it somehow controls the current. Generally, we observe that resistors have different colored bands on them. This is true for small-rated resistors that have a power rating of almost one watt. This color code scheme is designed by International Standard abbreviated as (IEC 60062). This standard gives the coding for resistors and other devices such as capacitors. For high-rating resistors, this standard also gives numerical codes.
There are several bands in color coding. These bands constitute the value of resistance, tolerance level, and also reliability factor or failure ratio in a few cases. Quantity of bands can be as few as three and at most six. In a few cases, two bands are also possible. In such a case, one indicates the value of resistance and the other gives the multiplier. Standardized resistances are also known as preferred resistances.
Chart for Color Code of Resistances
Given below is the chart that is used internationally for the calculation of resistances from given colored bands. This chart gives all three kinds of color codes that include resistor with 4 bands, resistor with 5 bands, and resistor with 6 bands
4-Band Resistors
It is the most readily available color-coding configuration. In resistors with four bands, Band 1 and Band 2 give a first and second significant figure of the resistance value, Band 3 is for the multiplier, and the last Band 4 shows the tolerance level.
5-Band Resistors
The main benefit of resistors with five bands is their high precision. It is because the third band here gives the third significant figure or resistance value, leading to high precision. Band four shows the multiplication factor, whereas the fifth band shows the tolerance level.
6-Band Resistors
In resistors with six bands, the first three bands indicate significant figures or resistance values. Band four shows the multiplication factor, whereas the fifth band shows the tolerance level. Moreover, the last sixth band describes the temperature coefficient of a resistor that explains how much temperature it can bear.
Resistance Color Code Table
This table shows the digit, multiplier, and tolerance level according to each colored band.
Examples of Calculation of Resistance Through Color Code
Example 1
In the example given below, there are five bands in the resistor having different colors that are orange, orange, black, brown, and violet. You need to find the value of each color band from the chart given above and also find the value of tolerance according to the fifth band’s color.
| First Band | Orange | 3 |
| Second Band | Orange | 3 |
| Third Band | Black | 0 |
| Fourth Band | Brown | 100 |
| Fifth Band | Violet | ± 0.1% |
Resistance Value = 3.3kΩ ± 0.1%
Example 2
In the example given below, again there are five bands brown, green, gray, silver, and red. Find their respective values from the chart given above to find the value of resistance.
| First Band | Brown | 1 |
| Second Band | Green | 5 |
| Third Band | Grey | 8 |
| Fourth Band | Silver | 0.01 |
| Fifth Band | Red | ± 2% |
Resistance Value = 1.58Ω ± 2%
Example 3
This example has only three bands. The absence of a fourth band will make it fall into the category of no fourth band and its tolerance will be ± 20%. The remaining values can be searched in the table given above.
| First Band | White | 9 |
| Second Band | Violet | 7 |
| Third Band | Black | 1 |
| Fourth Band | None | ± 20% |
Resistance Value = 97Ω ± 20%
Exceptional Cases in Color Code
Reliability band
For military purposes, the reliability band is also included in color coding. This band gives a percentage of the failure rate for every 1000 hours of use. It is generally not seen in commercial electronics. Reliability band is most of the time present on four band resistors.
One Black Band/ Zero-Ohm Resistor
There exists a resistor that has only one black band. This resistor is called a zero-ohm resistor. The main function of this resistor is to serve as a link that is used to connect traces while working on a Printed Circuit Board (PCB).
Five-Band Resistor with a Fourth Band of Gold or Silver
These resistors are utilized for old resistors where a temperature coefficient is necessary. So, bands one and two give significant figures, the third band shows the multiplying number, the fourth gives the tolerance level, and the fifth is used for the temperature coefficient (ppm/C˚).
Different Colors
For resistances with higher ratings, gold or silver colored bands are interchanged with yellow or gray. This is done to block metal particles from entering the coating of the resistor.
Conclusion
Color Codes of resistances are very handy to deal with. This is a standard that is accepted internationally, so you don’t have to worry about the value of your resistance, and you can easily calculate the ratings of your equipment where resistances are used.
