We can read the resistance value according to the resistors color code because of the use of four color bands or five color bands or six color bands on the resistors to indicate the resistance value. The color information representing the resistance value can be read at once from any angle.

Abstract

We can read the resistance value according to the resistors' color code because of the use of four-color bands or five color bands or six color bands on the resistors to indicate the resistance value. The color information representing the resistance value can be read at once from any angle. A resistor with color bands is the most widely used type of resistor in various electronic equipment. No matter how it is installed, Maintenance staff can easily read its resistance value for detection and replacement. The color band marking is mainly applied to cylindrical resistors, such as carbon film resistors, metal film resistors, metal oxide film resistors, fuse resistors, and winding resistors. In this article, I will briefly introduce you to how to read a resistor.

Catalog

I Resistors color code read sequence

Figure1. resistors with color code

In practice, it is found that the arrangement order of some resistors' color code is not clear, and it is often difficult to read. When identifying a resistor color code, you can use the following techniques to determine:

Tip 1: Find the color band that marks resistor tolerances first, and then you can determine the color band order. The most commonly used colors for resistor tolerances are gold, silver, brown, especially gold and silver bands, which are rarely used as the first band of the resistor color band. So as long as there are gold and silver bands on the resistor. It can be considered that this is the last band of the color band resistor.

Tip 2: Determine whether the brown band is the mark of resistor tolerances. The brown band is often used as both a band marks resistor tolerances and a valid number band. It often appears in the first band and the last band at the same time, making it difficult for people to identify who is the first band. In practice, it can be judged according to the interval between the color bands: For example, for a five-band resistor, the interval between the fifth band and the fourth band is greater than the interval between the first band and the second band.

Tip 3: In the case where the order of the color bands cannot be determined only by the distance of the color bands, the production sequence value of the resistor can also be used to judge. For example, there is a resistor color band reading order: brown, black, black, yellow, brown. The value is 100 × 10000 = 1MΩ, and the tolerance is 1%, which is the normal resistance value. If it is read in reverse order: brown, yellow, black, black, brown, the value is 140 × 1Ω = 140Ω, and the tolerance is 1%. The resistance values read according to the latter sort are not available in the series of resistance production, so the order of the latter color band is incorrect.

II Resistors color code read methods

Now, let's explore how to read resistor color code. In the early days, when the surface of the resistor was not enough to use digital representation, the method of color band marking was used to indicate the resistance, tolerance, and specifications of the resistor. It consists of two parts.

Part 1: The group near the front end of the resistor is used to indicate the resistance value.

Two significant digits of the resistance value are represented by the first three color bands, such as 39Ω, 39KΩ, 39MΩ. The resistance value of three significant digits uses the first four-color bands to represent its resistance value, such as 69.8Ω, 69.8Ω, 69.8KΩ, which is generally used for the precision resistance expression.

Part 2: A color band near the back of the resistor is used to represent tolerance accuracy.

Each color band in the first part is equidistant and self-contained, which is easy to distinguish from the color band in the second part.

Figure2. resistor bands

1. Three band resistors

The first color band is the tens digit, the second color band is the single digits, and the third color band represents the magnification. Its resistance value is indicated by the first three color bands, such as 39Ω, 39KΩ, 39MΩ.

2. Four band resistors

Identification of the four color band resistors: the first and second bands respectively represent the resistance value of two significant digits; the third band represents the magnification, and the fourth band represents the tolerance.

Example: Brown red red gold

Its resistance value is 12 × 10 ^ 2 = 1.2kΩ, the tolerance is ± 5%. The tolerance indicates the resistance value fluctuates above and below the standard value of 1200 (5% × 1200). It also indicates that the resistance is acceptable, that is, a good resistance between 1140-1260. The first and second bands with four color bands respectively represent the first two digits of the resistance value; the third band represents the magnification, and the fourth band represents the tolerance. The key to quick identification is to determine the resistance value within a certain order of magnitude according to the color of the third band, such as a few K or a few dozen K, and then substitute the numbers in the first two bands, in this way you can read the numbers quickly.

3. Five band resistors

Identification of the five color band resistor: the first, second, and third bands respectively represent the resistance value of three significant digits; the fourth band represents the magnification; the fifth band represents the tolerance. If the fifth color band is black, it is generally used as a winding resistor. If the fifth color band is white, it is usually used as a fuse resistor. If the resistor has only a black-colored band in the middle, it means that the resistor is a zero-ohm resistor.

Example: Red Red Black Brown Gold

Its resistance is 220 × 10 ^ 1 = 2.2KΩ, the tolerance is ± 5%. The first color band is the hundreds digit and the second color band is the ten-digit. The third color band is the single digit, and the fourth color band is the power of the color that should be multiplied. The fifth color band is the tolerance rate.

First, from the bottom of the resistor, find the color band that represents the tolerance accuracy. Gold represents 5% and silver represents 10%. In the above example, the color band at the end is gold, so the tolerance rate is 5%. From the other end of the resistor, find the first and second color bands and read their corresponding numbers. In the above example, the first three color bands are red, red, and black, so their corresponding numbers are red 2, red 2. Black 0, whose effective number is 220. Then read the fourth multiple color band, Brown 1. Therefore, the resistance we get is 220 × 10 ^ 1 = 2.2KΩ. That is, the resistance value is a normal resistance between 2090-2310. If the fourth multiple color band is gold, multiply the significant number by 0.1. If the fourth multiple color band is silver, multiply by 0.01.

4. Six band resistors

Identification of the six color band resistors: The first five color bands of the six color band resistors are the same as the five color band resistors, and the sixth color band represents the temperature coefficient of the resistor.

Tips: You can use Utmel's Resistor Color Code Calculator to easily calculate the resistance value based on color bands or color-coded stripes on a resistor!

III Resistors color code chart

Figure3. Resistors color code chart

Take the four-color band as an example:

(1) Remember the numbers represented by each color of the first and second bands. It can be remembered as follows: brown 1, red 2, orange 3, yellow 4, green 5, blue 6, purple 7, gray 8, white 9, black 0. Read them in this way, and repeat them a few times to remember.

Remember that the order of magnitude of the color of the third band is the key to quick understanding.  

Gold: 0.1

Black: 1

Brown: 10

Red: 100

Orange: 1,000

Yellow: 10,000

Green: 100,000

Blue: 1000,000

(2) From the perspective of magnitude, they can be divided into three major levels, that is: gold, black, and brown are ohmic; red, orange, and yellow are thousands of euros; green and blue are Megohm level. This division is for the sake of memory.

(3) When the second band is black, the color represented by the third band is an integer, that is, several, several tens, several hundred kΩ, etc. This is a special case when reading resistors color code, so pay attention to it. For example, the third band is red, so its resistance is a few kΩ. (The third band of the 4 band resistor or the fourth band of the 5 band resistor that is a multiple is the number of zeros after the significant digits. If it is a negative number, the decimal point of the significant digits is shifted to the left by a few digits.)

(4) Remember the tolerance represented by the color of the fourth band, that is 5% for gold; 10% for silver; 20% for colorless.

IV Resistors color code examples

Example 1: When the four-color bands are yellow, orange, red, and gold in sequence, because the third band is red and the resistance range is a few kΩ, the numbers "3" and "4" are represented by the two colors of yellow and orange respectively, and its reading is 4.3 kΩ. The fourth band is gold, indicating a tolerance of 5%.

Example 2: When the four-color bands are brown, black, orange, and gold in sequence, because the third band is orange and the second band is black again, the resistance value should be a whole dozen of kΩ. The number represented by brown is "1", and it reads 10 kΩ. The fourth band is gold with a tolerance of 5%.

In some cases that are difficult to distinguish, you can also compare the colors at the two starting ends, because the first part of the calculation, that is, the first color, will not be three colors: gold, silver, and black. If these 3 colors are close to the edge, you need to do the reverse.

There are two ways for color identification of color band resistors. One is the labeling method with 4 color bands, and the other is the labeling method with 5 color bands. The difference between the two is that the first two digits of the 4-color band represent the significant digits of the resistance, and the first three digits of the 5-color band resistor represent the significant digits of the resistance. The penultimate bit of the two represents a multiplier of the significant digits of the resistance. The last digit indicates the tolerance of the resistor.

For the 4 color band resistor, the calculation method of the resistance value is:

Resistance value = (the value of the first color band * 10 + the value of the second color band) * the multiplier represented by the third color band

For the 5 color band resistor, the calculation method of the resistance value is:

Resistance value = (the value of the first color band * 100 + the value of the second color band * 10 + the value of the third color band) * the multiplier represented by the fourth color band.