RESISTANCE CODE BY COLOR AND SMD VALUES

IDIOMA (LANGUAGE) : ESPAÑOL

We can find many different types of resistors available, to identify or calculate the value of a resistance it is important to have a marking system or using a measuring device such as the ohmmeter. The color code of the resistance is a way to represent the value in conjunction with the tolerance. The standards for color coding records are defined in the international standards IEC 60062, this standard describes the color coding for resistors with axial ends and the numerical code for SMD resistors.

There are several bands to specify the value of the resistance. Even the tolerance, reliability and failure rate are specified. The number of bands varies from three to six.

THREE-BAND RESISTANCE COLOR CODE

The use of the three-band color code is very rare.

• The first band that corresponds to the left end represents the most significant digit of the resistor.
• The second band represents the second most significant digit.
• The third band represents the power of 10 raised to the corresponding color and multiplied by the number obtained from the first and second bands.
• The tolerance for three band resistor is generally 20%.
For example, if the colors in the resistance are in the order of green, blue and red on the left, then the resistance can be calculated as 56 x 102 ± 20%. This is 5.6 KΩ ± 20%, this means that the resistance value is in the region of 4480Ω to 6720 Ω.

FOUR-BAND RESISTANCE COLOR CODE

This four-band color code is the most common representation in resistors.

• The first band that corresponds to the left end represents the most significant digit of the resistor.
• The second band represents the second most significant digit.
• The third band represents the power of 10 raised to the corresponding color and multiplied by the number obtained from the first and second bands.
• The fourth band represents tolerance.

There is a significant gap between the third and fourth bands, this gap helps to identify the reading direction.

For example, if the colors in a four-band resistance are in the order green, black, red and yellow, then the resistance value is calculated as 50 x 102 ± 2% = 500 KΩ ± 2%.

FIVE-BAND RESISTANCE COLOR CODE

The high precision resistors have an additional band that is used to indicate the third significant value of the resistance. The rest of the bands indicate the same parameters as the four-band color code.

• The first band that corresponds to the left end represents the most significant digit on the resistor.
• The second band represents the second most significant digit.
• The third band represents the third most significant digit.
• The fourth band represents the power of 10 raised to the corresponding color and multiplied by the number obtained from the first, second and third bands.
• The fifth band represents tolerance.

An exception occurs when the fourth band is gold or silver, in this case, the first two bands indicate the two most significant resistance digits, the third band is used to indicate the multiplier, the fourth band is used to indicate tolerance and the fifth band is used to indicate the temperature coefficient with units of ppm/K.

For example, if the colors in a five-band resistance are in the order red, blue, black, orange and gray, then the resistance value is calculated as 260 x 103 ± 0.05 = 260 KΩ ± 0.05%.

SIX-BAND RESISTANCE COLOR CODE

In the case of high precision resistors, there is an additional band to indicate the temperature coefficient.

• The first band that corresponds to the left end represents the most significant digit of the resistor.
• The second band represents the second most significant digit.
• The third band represents the third most significant digit.
• The fourth band represents the power of 10 raised to the corresponding color and multiplied by the number obtained from the first, second and third bands.
• The fifth band represents tolerance.
• The sixth band represents the temperature coefficient.

The most common color used for the sixth band is black, which represents 100 ppm/K, this indicates that for a change of 100°C in the temperature, there may be a change of 0.1% in the resistance value. In general, the sixth band represents the temperature coefficient. But in some cases it can represent the reliability and the failure rate.

For example, if the colors in a resistance of six bands are in the order orange, green, white, blue, gold and black, then the resistance is calculated as 359 x 106 ± 5% 100 ppm/K = 359 MΩ ± 5% 100 ppm/K.

CODE OF TOLERANCE IN LETTER FOR THE RESISTOR

The letter code for tolerance:

K and M should not be confused with kilo and mega ohms.

SMD resistance code

They are three types of coding systems used to mark the SMD resistors. Which are:

• Three-digit coding
• Four-digit coding
• E96 coding

THREE-DIGIT CODE

The first two numbers indicate the most significant value of the resistance and the third number indicates the multiplier by 10 in case the digit is 1, 100 in case the digit is 2 or 1000 in case the digit is 3 and so on.

A three-digit coded SMD resistor is shown below:

Some examples of three-digit codes are:

450 = 45 * 100 = 45Ω
221 = 22 * 101 = 220Ω
105 = 10 * 105 = 1 MΩ

If the resistance is less than 10Ω, then the letter R is used to indicate the position of the decimal point. For example:

3R3 = 3.3Ω
47R = 47 Ω

FOUR-DIGIT CODE

For more accuracy, a four-digit code is marked. The calculation is similar to the three-digit code. The first three numbers indicate the most significant value of the resistance and the fourth number indicates the multiplier.

A 4-digit coded SMD resistor is shown below.

Some examples under this system are:

4700 = 470 * 100 = 470Ω
1001 = 100 * 101 = 1 KΩ
7992 = 799 * 102 = 79.9 KΩ

For resistors less than 100Ω, R is used to indicate the position of the decimal point, for example:

15R0 = 15.0 Ω

E SERIES

The Electronic Industries Association (EIA) has specified a preferred standard value system for resistors and is called the E series. IEC 60063 is an international standard that defines the preferred numerical series in resistors (and also for capacitors, inductors and Zener diodes). The coding is based on the tolerance values, the different E series available are:

• E3 50% tolerance
• E6 20% tolerance
• E12 10% tolerance
• E24 5% tolerance
• E48 2% tolerance
• E96 1% tolerance
• E193 0.5, 0.25, 0.1% and higher tolerances

Although E3 coding is no longer used and E6 coding is rarely used. The E96 coding system is used for high precision resistors with a tolerance of 1%.

There is a separate coding system in the EIA E96 marking system. This system uses three figures to mark. The first two are numbers that indicate the three most significant digits of the resistance value. The third figure is a letter used to indicate the multiplier.

The EIA E96 marks in an SMD resistors are:

The EIA 96 code scheme for multipliers is shown below:

The EIA E96 code scheme for significant resistance values is shown below:

Some examples of the EIA E96 coding system are:

• 92Z = 887 × 0.001 = 0.887 Ω
• 38C = 243 × 100 = 24.3 KΩ