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Color coding inductors

colored marking chokeThe electronic color code was developed in the early 1920s by the Radio Manufacturers Association (now part of Electronic Industries Alliance (EIA)), and was published as EIA-RS-279. The current international standard is IEC 60062.

The EIA standard for cylindrical inductors specifies 4 coloured bands that encodes the nominal value of inductance and the tolerance, i.e. permissible deviation from the specified nominal value. The most commonly used coding 4 or 3 colored rings or dots.

The first two bands indicates the nominal value of inductance in µH, the third band indicates the multiplier, the fourth band indicates the tolerance. If there are only 3 color bands or dots, that means the coding ±20% tolerance. Colored band that represents the first digit of the nominal, may be greater than all the rest or there is a gap between 1-3 and 4th band. A wide silver 1th band with double width, located at one end of the coil, identifies the military standart radio-frequency coils. In this case the inductor have 5 bands. You can use the online calculator to easy determine the inductance of color coded inductors.inductor color code chart

Cylindrical molded choke coils series ES24 is a miniature ferrite core coil with two pins. Value of inductance and tolerance are indicated with colored bands. Bands 1st and 2nd define two digits of the nominal value (in micro Henry), between which a decimal separator, band 3th defines decimal multiplier, band 4th defines tolerance. Assign colors bands is given on right figure. For example, inductance, which is marked red, yellow, brown and black bands, has an inductance value of  2,4 * 10 = 24 µH and tolerance of  ±20%.

The military standard for cylindrical inductors specifies 5 coloured bands. The same colours are used as in the EIA 4 band code, but:
For band 1, a double width sliver band is used to signify Military Standard.

  • For values less than 10µH:
    • Bands 2, 3 and 4 indicate the value of inductance in µH
    • A gold band might be used in either band 2 or band 3. In either of these two bands, gold indicates a decimal point and band 4 is used as a digit instead of a multiplier band.
    • When no gold band is present in bands 2 or 3, band 4 is a multipier band.
      For example:
      • If bands 2,3 and 4 are red, gold, red the value would be 2.2 µH
      • If bands 2,3 and 4 are gold, yellow, violet the value would be 0.47 µH (470nH)
      • Band 5 indicates the tolerance between 1% and 20%
  • For values of 10µH or more:
    • Bands 2 and 3 represent basic value, and band 4 gives the number of zeros.
    • For example:
        If bands 2, 3 and 4 are red, violet, orange the value would be 27000 µH

The online calculator help you to encode Military Standard color coding inductor.

For inductors of a very small physical size, coloured dots may be used instead of bands. In such cases, The silver dot indicating a Military specification will be larger than the other dots and will be placed a the beginning of the dot sequence.

In some cases only a single coloured dot is used, and for their meaning it is neccesary to refer to individual manufacturers data for accurate interpretation.

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