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Understanding resistor color codes

Often time, resistor values are indicated with color codes, that is, all leaded resistors with a power rating of up to one watt are marked with color bands. The color coding is described in the international standard IEC 60062. This standard explains the marking codes for resistors and capacitors. Numerical codes are also used in the color bands, often in surface mount SMD Resistors. Color codes are given by several bands, labeled around the resistors. They specify the resistance value, tolerance, and sometimes the reliability or failure rate. The number of bands varies from three to six, although resistors with two bands indicate the resistance value and one band serves as a multiplier. These resistance values are standardized and are called preferred values.

 

In this article, you’ll get to know the color codes of resistors, the chart, and tips for reading color codes.

Read more: Understanding resistors

What are resistor color codes?

Resistor color codes are color bands or numerical codes wrapped around resistors so that their properties such as power rating, value, tolerance, and reliability of a resistor. Below are tips to know when reading the codes of resistors:

  • The reading direction is not always clear. Sometimes the increased space between bands 3 and 4 provides an indication of the reading direction. The first band is usually the closest to a lead, a gold or silver band is always the last band and it indicates tolerance.
  • Checking the manufacturer’s documentation is also essential to be sure about the color-coding system used.
  • The resistance should be measured with an ohmmeter, if not sure. In most cases, this might be the only way to figure out the resistance; for instance, when the color bands are burnt off.

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Color code resistor chart

The chart below shows how to determine the resistance and tolerance for resistors. This table can also be used to specify the color of the bands when the values are known, although an automatic resistor calculator can be used to quickly find the values of the resistors.

Color code resistor chart

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Four band resistors

The four-band color code is the most common variation, having two bands for resistance value, one multiplier, and one tolerance band. In the below figure, the 4 bands are green, blue, red, and gold. In the color code chart, you’ll determine that green stands for 5 and blue for 6. The third band is the multiplier, with red representing a multiplier value of 2 (102). Thus, the value of the resistor is 56 · 102 = 56 · 100 = 5600 Ω. Finally, the gold band indicates the tolerance of the resistor which is 5%. The resistance lies between 5320 and 5880 Ω (5560 ± 5%). Sometimes the tolerance band is left blank, then the result of the band 3 resistor. This means, the resistance value remains the same but the tolerance is 20%.

Four band resistors

5 band resistors

High precision resistors have an extra band to indicate a third significant digit. Thus, the first three bands indicate the significant digits, the fourth band is the multiplication factor, and the fifth band represents the tolerance. In the below diagram: brown 1, yellow 4, violet 7, black (x 100 = x1), green (0.5%) representing 147 Ω resistor with a 0.5% tolerance. There are exceptions to the 5-band color system, sometimes the extra band may indicate failure rate (military specification) or temperature coefficient (older or specialized resistors).

5 band resistors

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6 band resistors

Resistors with six bands are usually for high precision resistors, having an additional band to specify the temperature coefficient (ppm/˚C = ppm/K). The most common color for the sixth band is brown (100 ppm/˚C). this means a temperature change of 10 oC, the resistance value can change 1000 ppm = 0.1%. for the 6-band resistor shown below: orange 3, red 2, brown 1, brown (x10), green (1%), red (50 ppm/oC) represents a 3.21 kΩ resistor with a 1% tolerance and a 50 ppm/°C temperature coefficient.

6 band resistors

Color code exceptions

Reliability band:

Resistors are made based on military specifications; sometimes the extra band is included to indicate reliability. It is specified in the failure rate (%) per 1000 hours of service. Such is rarely seen in commercial electronics; the reliability band is often found on four band resistors. The US military handbook MIL-HDBK-199 has more information about reliability.

Single black band or zero-ohm resistor:

Resistors with a single black band are known as a zero-ohm resistors. Normally, it is used as a wire link that functions to connect traces on a printed circuit board (PCB). Using the resistor package allows the same automated pick-and-place machines to place the components on a circuit board.

5 band resistors with silver or gold 4th band:

Five band resistors with the fourth band of gold or silver create an exception and are used on specialized and older resistors. The two first bands represent the significant digits, the 3rd is the multiplication factor, the 4th is the tolerance, and the 5th is the temperature coefficient.

Read more: Understanding varistor

Deviating colors:

in high voltage resistors, the colors gold and silver are often replaced with yellow and gray. This is to eliminate metal particles in the coating.

Watch the video below to learn more about the color code of resistors:

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That is all for this article, where the definition, tips, and exceptions of resistors color codes are being discussed. I hope you got a lot from the reading, if so, kindly share with other students. Thanks for reading, see you around!

 

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