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Review of Okaphone: Resistor Calculator

Go to the Resistor Calculator on the Okaphone site

You can use this tool to determine the value of a color coded resistor by selecting the color bands in the picture (if you want to learn about the coding scheme, you can look e.g. at page 6 of Analog Electronics Lecture 4 Resistors). Or you can type in an arbitrary number and let the tool determine the nearest resistor in the selected E-series. It will even tell you how you can come closer to the desired value by using 2 resistors, either in parallel or in series.

However, the determination of the resistors value is not foolproof, even with this nice tool. In some cases it is difficult to know at which end of the resistor you have to start. You might even mistake one color for another (red/orange, red/brown, blue/violet...). This may also depend on the ambient light, the same color will look different in sunlight and in the light of a fluorescent lamp. So if the resistor is not yet soldered into the PCB, it is generally a good idea to check your result with a digital multimeter.

You may also be interested in some other Recommendations for Resistor Resources.

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