When assembling electrical circuits, the radio amateur often has to deal with the determination of the value of unknown components. The resistor is most commonly used. Frequent questions arise with its designations. Translated from English, this name sounds like "Resistance". They differ in both nominal resistance and power handling. In order for the master to choose an element with the desired denomination, a designation is applied to their bodies. Depending on the type of resistors, the coding may differ, it can be: alphanumeric, digital or color stripes. In this article, we will tell you in more detail what is the marking of domestic and imported resistors, as well as how to decipher the designations indicated by the manufacturer.
Content:
- Denomination of denomination in letters and numbers
- How to determine the denomination by the color rings
- SMD resistor marking
Denomination of denomination in letters and numbers
Alphanumeric marking of resistors and color stripes (rings) are used on Soviet-made resistances. An example can be considered resistors of the MLT type, on them the resistance value is indicated in an alphanumeric way. Resistors up to hundreds of Ohms contain the letter "R", or "E", or "Ω" in their marking. Thousands of Ohms are marked with the letter "K", millions with the letter M, i.e. the order of magnitude is spelled out. In this case, whole units from fractional ones are separated by the same letters. Let's take a look at some examples.
In the photo from top to bottom:
- 2K4 = 2.4 kOhm or 2400 Ohm;
- 270R = 270 Ohm;
- K27 = 0.27 kOhm or 270 Ohm.
The marking of the third is incomprehensible, perhaps it is deployed on the wrong side. In addition, power markings may be present on resistors from 1 W. The marking is quite convenient and clear. It may differ slightly depending on the type of resistors and their year of manufacture. There may also be an additional letter that indicates the accuracy class.
Import resistances, including Chinese ones, can also be labeled with letters. A prime example is ceramic resistors.
The first part of the designation indicates 5W - this is the power of the resistor equal to 5W. 100R means that its resistance is 100 ohms. The letter J speaks about the tolerance of deviations from the nominal value equal to 5% in both directions. The complete tolerance table is shown below. The accuracy class or permissible deviation from the rating does not always significantly affect the operation of the circuit, although it depends on their purpose.
How to determine the denomination by the color rings
Recently, outlet resistances are more often indicated with the help of color stripes, and this applies to both domestic and foreign elements. Depending on the number of color stripes, the way they are decoded changes. In general, it is assembled in accordance with GOST 175-72.
Resistors can be color coded with 3, 4, 5 and 6 color rings. In this case, the rings can be displaced to one of the terminals. Then the ring that is closest to the wire lead is considered the first and the decoding of the color code begins with it. Or one of the rings may be missing, usually the penultimate one. Then the first is the one near which there is a couple.
Another option is when the marking rings are evenly spaced, i.e. fill the surface evenly. Then the first rings are determined by the colors. Suppose one of the extreme rings (the first) cannot be gold, then you can determine which side the report is coming from.
Pay attention with this method of marking from 4 rings, the third ring is a multiplier. How do I understand this table? Take the top resistor, the first ring is red, this is 2, the second purple is 7, the third, the red multiplier is 100, and our brown tolerance is 1%. Then: 27 * 100 = 2700 Ohm or 2.7 kOhm with a tolerance of 1% deviation in both directions.
The second resistor is color coded with 5 strips. We have: 2, 7, 2, 100, 1%, then: 272 * 100 = 27200 Ohm or 27.2 kOhm with a tolerance of 1%.
Resistors of 3 strips are color-coded according to the following logic:
- 1 strip - units;
- 2 lane - hundreds;
- 3 lane - multiplier.
The accuracy of these components is 20%.
The ElectroDroid program will help you decipher the color designation, it is available for Android in the Play Market, its free version has this function.
Another way of decoding the color code from Philips involves the use of 4, 5 and 6 stripes. Then the last strip carries information about the temperature coefficient of resistance (how much the resistance changes with a change in temperature).
Use the table to determine the denomination. Pay attention to the last column - this is TCS.
On the body, the colored rings are distributed, as shown in this diagram:
You can learn more about how to decipher the marking of resistors from the video data:
SMD resistor marking
In modern electronics, one of the key factors in device design is its miniaturization. This causes the creation of leadless elements. SMD components are small in size due to their leadless design. Do not be confused by this mounting method, it is used in most modern electronics and has good reliability. It also simplifies the design of the multilayer PCB. Literal transcript with translation means "device for surface mounting", and they are mounted on the surface of the printed circuit board. Due to the miniature size, difficulties arise with the designation of their rating and characteristics on the case, therefore they compromise and use methods of marking by numbers, with letters or using a code system. Let's see how SMD resistors are labeled.
If 3 digits are applied to the SMD resistor, then the decoding is done as follows: XYZ, where X and Y are the first two digits of the nominal, and Z is the number of zeros. Let's look at an example.
It is possible to designate with 4 digits, then everything is the same way, only the first three digits are hundreds, tens and ones, and the last one is zeros.
If letters are entered into the marking, then the decoding is similar to domestic MLT resistors.
And integers are separated from fractional values.
Another thing is when alphanumeric coding is used, such resistors have to be deciphered according to tables.
In this case, the letter denotes the multiplier. In the table below, they are circled in red.
Based on the table, cipher 01C means:
- 01 = 100 Ohm;
- C - multiplier 102, this is 100;
- 100 * 100 = 10000 Ohm or 10 kOhm.
This designation is called EIA-96.
The information contained in symbolic or color coding will help you build circuits with high accuracy and use elements with appropriate ratings and tolerances. A correct understanding of the notation does not relieve you of the need to measure resistance. It is still better to check it again, because the element may be faulty. The check can be done with a special ohmmeter or multimeter. We hope that the information provided on what is the marking of resistors and how it is deciphered was useful and interesting for you!
Related materials:
- How to check a resistor at home
- Color coding of wires
- How to determine the capacitance of a capacitor
- How to properly solder radio components from boards
