Resistor Colour Coding, what is it and where is it used?

To get a better understanding we need to go back to the basics…

A resistor is an electrical component that limits or regulates the flow of electrical current in an electronic circuit. Resistors can also be used to provide a specific voltage for an active device such as a transistor.

Resistors are usually very small, and it is difficult to print the resistance values on them. So, for identification purposes coloured bands, known as resistor colour codes, are printed on them.

But how do you read them and what do they mean?

The “left-hand” or the most significant coloured band is the band which is nearest to a connecting lead with the colour coded bands being read from left-to-right as follows:

Digit, Digit, Digit, Multiplier = Colour, Colour x 10 colour  in Ohm’s (Ω)

Blue Grey Black Red = 6802 = 680 x 102 = 68KΩ

The fourth and fifth bands are used to determine the percentage tolerance of the resistor.

Most five band resistors are precision resistors with tolerances of either 1% or 2% while most of the four band resistors have tolerances of 5%, 10% and 20%. The colour code used to denote the tolerance rating of a resistor is given as:

Brown = 1%, Red = 2%, Gold = 5%, Silver = 10 %

If the resistor has no fourth tolerance band then the default tolerance would be at 20%.

Where else are these colour codes used?

Most broadcast products use the “Resistor Colour Code” because the colour code has been used for many years by designers and installers alike. Traditionally, individual coloured ferrules are used in these applications.

The use of the colour coding makes it easy to distinguish the cable ident at a distance, however, the application of these individual ferrules can be time consuming particularly on large projects and requires the stock to be readily available to the installer.

So, how can you save time and money when applying cable idents that incorporate the Resistor colour code?

Silver Fox is the only company to provide Resistor colour coding in its labelling software, this functionality was introduced in 2008.

The resistor colour code functionality is available in the Labacus® Innovator Professional and Advanced software and the application would be most suited to the Prolab® Laser Wrap Around labels. – These are ideal where termination is completed or for maintenance and repair, the label ident can be printed all around the cable making it visible from all angles.

Another option is the Prolab® Laser 2-part system – suitable for any application where the ID is likely to need frequent changes.

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