Rows of resistors, capacitors, inductance ratings

Have you ever wondered why there are 1.2 kΩ resistors, but not, for example, 1.25 kΩ? The thing is that the nominal values ​​of radio components are not chosen according to the principle “the manufacturer just wanted to”. They are standardized and in this article we will tell you what are the series of ratings for radio components: resistors, capacitors and inductors.

What it is

A number of ratings are typical values ​​of the nominal values ​​of electronic components. In addition to the size, they also determine the permissible deviations for this group of parts. Standardization of resistance, capacitance and inductance values ​​for industrially manufactured products is necessary to match products manufactured in different countries.

A number of denominations are designated by the Latin letter E and numbers. The numbers reflect the number of nominal values ​​of the resistances of the resistors, the capacitance of the capacitors or the inductance of the coils in it. For example, in E3 - 3 values, and E24 - respectively 24.

The letter E means it complies with EIA (Electronic Industries Alliance) standards.

The beginning of the standardization process was laid back in 1948 at the Technical Committee No. 12 "Radio Communication", when the nominal values ​​close to E12 were given. And already in 1950 the E6, E12, E24 were developed. As a result, only 7 series of standard values ​​and tolerances of deviations (errors) from them were adopted. What is it for?

Suppose there is a number "1.0" in E6, which means that all resistors must have resistance in fractions of this number (if divided) or multiplied by 10ⁿ_. For example:

1,0*10²=100

This means there may be a 100 ohm resistor. The next digit in the set is "1.5". That is, there is no 120 Ohm element in the E6 set of values, it may already be 150 Ohm. Why is this done?

As we have already mentioned, certain tolerances are tied to each row, for E6 it is ± 20%, which means that the resistance of the "100 Ohm" resistor in this case can be from 80 to 120 Ohm. To "dilute" these values ​​further from each other, a certain step was chosen.

The step is also not chosen arbitrarily, the set of denominations is a table of decimal logarithms, you can calculate the value of any member of the series using the formula:

where n is the member number and N is the row number (E3, E6, etc.).

Let's take a closer look at this issue.

Denomination tables

Immediately, we note that the numbers from all series are the same for capacitors, and for resistors, and for chokes. But there are some peculiarities. Let's make a reservation right away that the most common are:

• E3 (currently almost not used, but you can find old elements corresponding to it);
• E6;
• E12;
• E24;

As we have already said, the permissible deviation from the indicated denomination depends on the series of denominations to which the electronic component belongs. You can see the table of tolerances below:

Row	Tolerance
E3	±50%
E6	±20%
E12	±10%
E24	±5%
E48	±2%
E96	±1%
E192	± 0.5%, 0.25%, 0.1% or more

It turns out that the error of the elements corresponding to the values ​​from E3 can differ by half in both directions, while the common E24 has only 5 percent. Let's consider typical values.

For resistors

On the market you can find resistances from all the existing series, except that E3 is not found in new components. The table below shows the values ​​for groups E3, E6, E12, E24, the last three are most common.

We also give values ​​from the series of ratings E48, E96, E192.

Newbies often ask, "How do you use these numbers?"

It's pretty simple. Imagine you are calculating a resistor for a circuit. As a result, it turned out that an element with a resistance of 1170 ohms is needed.

After analyzing what you can buy in the nearest store, we decided that we need to choose from the volume of E24 values ​​and saw that there are numbers 1.1 and 1.2. These numbers need to be multiplied or divided by 10 so many times to get a value close to your calculations, for example:

1.1 * 10 * 10 * 10 = 1100 Ohm

1.2 * 10 * 10 * 10 = 1200 Ohm

Here 1200 ohms or 1.2 k ohms is closer to 1170 ohms than 1.1 k ohms. This means that you have already selected a suitable value from the range of E24 ratings. Thus, you can choose the correspondence of the calculated resistor to the real one, which you can find on sale or in your bins.

For capacitors and inductors

With the capacity of constant capacitors, the situation is similar. But most often there are on sale items from the series EZ, E6, E12, E24, less often E48, E96 and E192. This is because capacitors with smaller tolerances are difficult to manufacture.

The way of using the above tables is the same. For example, below we will place a table with the code designation and the nominal capacitance of capacitors from E3 and E6 in pico- and microfarads.

Inductors or, as they are also called, the chokes are produced by manufacturers according to the same rules - the inductance most often corresponds to the values ​​from E12 or E24.

It should be noted that most electronic circuits do not require high accuracy in the selection of electronic components and a deviation of 5 or even 10% is considered quite acceptable. Moreover, having bought several identical parts, you can measure their real resistance, inductance or capacitance and select the ones that are closest to the calculated ones. Also take into account the peculiarities of the device, for example, how the ratings of the elements change at different temperatures. This is all that we wanted to tell you about the ranks of the denominations of radio components.

Related materials:

• How to solder radio components from boards
• SMD resistor marking calculator
• Online calculation of energy in a capacitor