Most resistors used in electronic circuits are too miniscule to have resistance values written on their package. Therefore, the resistance value is generally represented by colour bands. Even for larger resistors, it is regularly more convenient to use colour bands because printed numbers would be too difficult to determine if the resistor is dirty or not oriented correctly. However, there are issues with color bands as well, as overheating or dirt accumulation, may make it difficult to distinguish brown from red from orange.
The use of color bands allows for simple and fast understanding of resistance values on a printed circuit board. There are a few variances of the basic color coding scheme, where there could be 3, 4, 5, and even 6 color bands on a resistor. They are arranged such that the bands are nearer to one end of the resistor, and they are read in order beginning from that end.
The 1st and 2nd bands represent the 2 significant digits which designate the numerical value of the resistor, while the colour of the third band usually determines the power-of-ten multiplier. For instance, a resistor that has brown, red, and orange bands would have a value of .
Because of imperfections, resistors are never the exact value that the colour codes indicate. As such, a 4th band is commonly used to identify the tolerance, which is a percentage measure of accuracy. Standard tolerance levels are 5%, 10%, and 20% for carbon-composition and carbon film resistors. If there's no fourth band present, the tolerance is assumed to be 20%. The red, gold, and silver bands represent 2%, 5%, and 10% tolerances respectively.
Metal oxide resistors are more widely used nowadays due to their lower temperature coefficient and better tolerances, which are available down to 1%, with 2% or 5% being standard.
The use of color bands allows for simple and fast understanding of resistance values on a printed circuit board. There are a few variances of the basic color coding scheme, where there could be 3, 4, 5, and even 6 color bands on a resistor. They are arranged such that the bands are nearer to one end of the resistor, and they are read in order beginning from that end.
The 1st and 2nd bands represent the 2 significant digits which designate the numerical value of the resistor, while the colour of the third band usually determines the power-of-ten multiplier. For instance, a resistor that has brown, red, and orange bands would have a value of .
Because of imperfections, resistors are never the exact value that the colour codes indicate. As such, a 4th band is commonly used to identify the tolerance, which is a percentage measure of accuracy. Standard tolerance levels are 5%, 10%, and 20% for carbon-composition and carbon film resistors. If there's no fourth band present, the tolerance is assumed to be 20%. The red, gold, and silver bands represent 2%, 5%, and 10% tolerances respectively.
Metal oxide resistors are more widely used nowadays due to their lower temperature coefficient and better tolerances, which are available down to 1%, with 2% or 5% being standard.
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