Question

In the absence of a digital millimeter, the value of a resistor can be decoded using the color bands printed on the body of the resistor. Using online resources, describe the 4-band-code and 5-band-code coding/decoding process. What are the disadvantages of using the color coding technique?

Answer 1

4 BAND COLOUR CODING

4 band color code resistor has 3 color bands on left side and one color band on right side. The 3 color bands on left side are very close to each other and the 4^th color band on right side is separated from first 3 bands with some space.

The 3 color bands on the left side are grouped together to indicate the resistors resistance value and the 4^thcolor band on the right side indicates the tolerance of the resistor.

The 1^st color band on the resistor indicates the 1^stsignificant value or 1^st digit of the resistors resistance and the 2^nd color band indicates 2^nd significant value or 2^nd digit of the resistors resistance. The 3^rd color band is the decimal multiplier and the 4^th color band indicates the resistors tolerance.

The 1^st and 2^nd color bands together make up a 2 digit number and the 3^rd color band or multiplier is multiplied with this 2 digit number to obtain the resistance value of the resistor.

If the 4^th color band or tolerance band is left blank, it is considered as the 3 band resistor and the tolerance for the 3 band resistor is assumed to be 20%.

Resistors that are manufactured for military use may also include an extra band called 5^th band which indicates resistor failure rate.

Example:

If the colors on a 4 band resistor is in this order: brown, green, red and violet (as shown in figure). The values of color bands will be like this: Brown = 1, Green = 5, Red = 10² or 100, Violet = 0.10%.

The first and second color bands are grouped together to make up a two digit number 15. The 3^rd color band red has a value of 100. This value is multiplied with the two digit number I.e., 15 x 100 = 1500 ohms. Violet specifies that the tolerance is 0.10%.

Therefore, the resistor color coded with brown-green-red-violet would have a resistance of 1500 ohms with a tolerance of ± 0.10%

5 BAND COLOUR CODING

A 5 band color code resistor has 4 color bands on left side and one color band on right side. The 4 color bands on left side are very close to each other and the 5^th color band on right side is separated from the first 4 bands with some space.

The 4 color bands on the left side are grouped together to represent the resistance value of a resistor and the 5^th color band on the right side indicates the tolerance of the resistor.

• The 1^st color band indicates the 1^st significant value or 1^st digit of the resistors value.
• The 2^nd color band indicates the 2^nd significant value or 2^nd digit of the resistor value.
• The 3^rd color band indicates the 3^rd significant value or 3^rd digit of the resistors value.
• The 4^th color band is the decimal multiplier.
• The 5^th color band indicates the resistors tolerance.

The 1^st, 2^nd and 3^rd color bands together make up a 3 digit number and the 4^th color band or multiplier is multiplied with this 3 digit number to obtain the resistance value of the resistor.

Example:

If the colors on a 5 band resistor is in this order: brown, green, red, blue and violet (as shown in figure). The values of color bands will be like this: Brown = 1, Green = 5, Red = 2, blue = 10⁶, Violet = 0.10%.

1^st digit, green has a value of 5 which is the second digit and red has a value of 2 which is the 3^rd digit. The first, second and third color bands together make up a three digit number 152. The 4^th color band blue has a value of 10⁶. This value is multiplied with the three digit number 152 I.e., 152 x 10⁶ = 152MΩ. Violet specifies that the tolerance is 0.10%.

Therefore, the resistor color coded with brown-green-red-blue-violet would have a resistance of 152MΩ with a tolerance of ± 0.10%.

How to read or decode resistor color codes

The placement of the color bands on the resistor is very important. Generally, the color bands placed closest to the lead or end of the resistor is considered as the first band. The next to the first band is second band and so on. Another way is the extra space between the two bands (3^rd and 4^th bands) also indicates the reading direction.

If you feel difficult to find the resistance of the resistor by using its color bands, you can directly find the resistance by using ohmmeter or multimeter.

DISADVANTAGES OF COLOUR CODING

The color coding technique has somed  For blind people, it is impossible to find the resistance of the resistor, because they cannot see the colors coated on the resistor. Another  drawbacki recognizing the difference between two colors in an over heated resistor is very difficult.