The Learning Circuit 21: Reading Resistor Chart Values

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 In this episode, we learn how to read resistor coders to learn the values of resistors.  Many electrical components are marked with these values.  You’ll also learn how to differentiate through-hole resistors and surface mount resistors, as well as, determine the values of four band and five band resistors.  If you have any questions or comments on resistors codes let us know in the comments below..

Many electrical components are marked with their values.  Since parts can get quite small and numbers can get quite large, sometimes those values are written in a code.  Look at a list of standard resistor values.  Compare the abbreviated numbers with those on the prefix chart.  A resistor that is 4700 ohms is called 4.7 K ohms or kilo ohms.  A 100,000 ohm resistor is 100 kilo ohms.  A one million ohm resistor is 1 mega ohm.

There are through-hole resistors and surface mount resistors.  Through-hole resistors have color bands on them. Resistors use a color coding system to indicate their value as well as their tolerance. Tolerance is the accuracy or margin of error of the resistor rating. This can Range anywhere from a fraction of a percent up to 20 percent.  You can use the color coded resistor chart below to determine the digit multiplier or the tolerance that the color band represents.  Resistors can have a varying number of bands on them. We’ll focus on four and five band resistors as they are the most common.  On a four band resistor the first two stripes are combined together to form a number between 1 and 99.  The third stripe is the multiplier and the last stripe marks the tolerance.  On a five band resistor, the first three stripes get read as a single number, while the fourth stripe is the multiplier and the fifth band represents the tolerance.  Most five band resistors are precision resistors with tolerances of 1% or 2% indicated by a brown or a red band on the far right. While most of the four band resistors have tolerances of 5% or 10% indicated by a gold or a silver band.  If the resistor has no fourth tolerance band then the default tolerance would be 20%.

Resistors with a single black band are zero ohm resistors. Since they have the same packages as other resistors they can easily be placed on a PCB by automated machines. They’re often used as wire simply to connect traces.  Karen shows you how to figure the values of some four and five band resistors.