Daily Archives: 11-May-2016

I have been designing circuits with resistors since I was a kid working on science fair projects – I still remember building my first Radio Shack photocell project. While I have always thought of resistors as simple devices, I recently discovered that I have been laboring under a misconception about the standard resistor values.

Until last week, I believed that the values of the E-series standard resistor values were selected to ensure that if I needed a resistor within x% of a specific value, I simply needed to choose a resistor from the x% tolerance set. For example, Figure 1 shows the E12 series (i.e. ±10%) values – notice that each tolerance range overlaps the adjacent ranges. This means that you can always find an E12 resistor value within 10% of your required value. Continue reading →