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|The Learning Circuit|
|The Ben Heck Show|
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.