Determining the nominal resistance value of a resistor by marking with color stripes: online calculator

Resistor, especially low power - a small radio element. But it is necessary to apply the denomination marking on it. This is especially important in industrial settings. If a radio amateur in a home laboratory can check every resistance, then in production there is no such possibility. On small (0.125 W or 0.25 W) resistors, the designation was previously applied in small numbers, it was not easy to read them. Yes, and it is technologically difficult to apply such marking. Therefore, many manufacturers began to switch to the coded designation of the denomination of the output device with colored stripes or dots. The second option did not receive much distribution, and the first turned out to be convenient for manufacturers, so it took root. Now even large resistors (up to several watts) are marked this way.

The number and purpose of colored stripes on the resistor

The main characteristics of the resistor are:

• power (in watts);
• nominal resistance (in ohms);
• accuracy (scatter from the nominal value in percent);
• temperature coefficient of resistance - the relative change in resistance with a change in temperature (measured in ppm / ° С - how many parts per million (part per million) the resistance of the resistor will change from the nominal value when the temperature changes by 1 degree Celsius).

The first parameter in the list is determined by the dimensions of the element. The larger the size, the more heat output it can dissipate during operation. Other characteristics are marked with colored annular stripes located along the body.

Most of the designation is occupied by the nominal resistance of the device - it consists of two or three rings, meaning numbers and one strip, meaning the multiplier by which the first value must be multiplied. And in total, from 3 to 6 bands can be applied to the resistor:

• three bands are applied to resistors with an error of up to 20% (the least accurate) - two rings indicate the face value, and the third gives information about the multiplier (accuracy is not indicated in this case);
• four rings - everything is the same as in the previous version, but the requirements for the error are more stringent - from 10% or less (in most cases, four bands have resistances of an accuracy class of ± 10% and ± 5%);
• five bars - as in the case of four, but the denomination digits are indicated by three rings, then the decimal multiplier and the scatter bar (2.5% or less);
• six rings have high-precision resistors designed to work in difficult conditions, in addition to the previous option, they have an additional strip indicating the temperature coefficient of resistance.

Important! There are resistors marked with a single black stripe. Their resistance is zero, they serve as jumpers on the printed circuit board. The use of such resistances is associated with the features of the topology of printed circuit boards and the technology for manufacturing electronic devices in industrial conditions.

Significant figures

Significant figures show the value of the resistor without taking into account the multiplier. For example, for a device with a resistance of 10 Ohm, 100 Ohm, 1 kOhm, 10 kOhm, etc. the first two familiarity will be the same color - brown, then black. For more accurate elements, often having a fractional value (for example, 10.2 ohms), three digits (three bars) are used for this category.

You can determine the color values ​​​​from the tables that are available in the reference literature or on the Internet. But it is most convenient to use special calculators. Previously, they were used in the form of programs that had to be downloaded to a computer. Online calculators are now widely used. They allow you to sequentially add colors to the form without worrying about remembering the previous numbers and, as a result, get the required resistance value.

There is a problem in practice. Some manufacturers, especially little-known ones, use dyes of difficult-to-identify colors for marking. And if gray can be distinguished from silver by the location of the ring, then completely indistinct shades often do not allow differentiating yellow from orange or red from brown.A possible reason for this approach is to save on the cost of paint. The only way out in this case is to directly measure the resistance with a tester.

Multiplier x10

To distinguish, as mentioned above, 10 ohms from 10 kilo-ohms, there is one more parameter in the marking - a decimal multiplier. It shows by what to multiply the result obtained in the previous step. So, if the third strip of four is black, then the multiplier is 1 and the total result is 10 ohms. But if this ring is orange, then you need to multiply by 1000, and the result is 10 kOhm. The range of this parameter is from 0.01 to 10⁹, 11 colors are used to encode the entire range. For convenience, often for each color not a decimal multiplier is indicated, but a prefix of a decimal multiple of one. So, green means that the value must be multiplied by 100 kOhm (by 10000), and blue means by 1 MΩ (multiplication by a million).

Permissible deviation from the nominal value in %

This parameter shows how the actual resistance value may differ from the declared one. So, with a 10% spread, the resistance of a 10 kiloohm element can have a value in the range from 90 to 110 kOhm. For solving many problems in household and amateur equipment, this accuracy is quite sufficient, and most devices in the wide market fit into just such an error.

But for measuring technology, such a spread is already too large. Even a difference of 5% is not always enough. Therefore, for such purposes, resistors with a spread of 2% or more are used. A separate strip is allocated for marking this parameter. Silver to gray color indicates ±10% to ±0.05% variation.

Temperature coefficient of resistance in ppm/°C

In a home laboratory, and even in household appliances, the likelihood of using rather expensive resistors for which this parameter is important is small. But in mission-critical applications, where stable operation under temperature changes is important, information about the resistor's response to heating or cooling can be critical. And for high-precision resistors, a sixth strip is provided, on the far right, indicating TKS. 7 colors are allocated for it - for coefficients from 1 to 100 in ascending order. A coefficient of 1 means that when heated by 1 ° C, the resistance will change by a millionth of the nominal value, that is, by one ten thousandth of a percent.

Which side to count the strips on the resistor

To determine the value, the resistor marking is read from left to right. The body of the resistor is symmetrical, so sometimes it takes time to determine the sides. The search algorithm is as follows:

• if there is a silver or golden stripe on the body, then it is always on the right (if space permits, it is applied a little to the side);
• if space permits, the rings are always shifted towards the left side;
• sometimes the first strip is made wider than the rest;
• if there are no listed signs, you can try to read the marking in one direction, then in the other - it may turn out that the denomination cannot be determined in one direction (for example, black is not used for TKS).

If none of the methods helped, it remains measure the resistance with a multimeter.

Color Stripe Resistor Marking Calculator

Rows of Preferred Values ​​for Resistors

Resistors are available in ratings corresponding to a range of preferred values.These series are defined by standards adopted in many countries in accordance with international agreements (IEC 63-53).

In Russia, this standard is GOST 28884-90. It provides for the release of resistors in the series E3, E6, E12, E24, E48, E96 and E192. The series differ from each other in the step of values ​​(which should be multiplied by a decimal coefficient). And the step depends on the tolerance, which decreases with the growth of the digital index. So, the smallest error (0.5%, 0.25% and 0.1%) and the smallest step of ratings have resistors from the E192 series.

Rows with a lower index are obtained by deleting even values ​​from the higher row. And the rows E3 and E6 have the smallest accuracy (20%) and the largest step. The latter contains only 3 denominations. And this is logical - there is no point in a small step if the next value does not go beyond the allowable spread. You can get acquainted with the filling of the rows by reading GOST. You can download it on the Internet.

Table 1. Rows of preferred values ​​​​for resistors E24, E12, E6, E3.

Table 2. Rows of preferred values ​​for resistors with tight tolerances E192, E96, E48.

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