Because it is very easy to miss decimal points (or decimal commas) in parts lists, a convention for writing resistances has developed. By this convention, the decimal separator is replaced by a letter based on the multiplier, for example, “K” (for thousand) or “M” (for million). So, for example
|4,700 =||4.7K =||4K7|
|4,700,000 =||4.7M =||4M7|
Where the multiplier is 1 the letter “R” is used. The symbol Ω was not used because it is not available on many printers. For example:
|0.68 =||R68 (multiplier is 0.01, silver)|
|6.8 =||6R8 (multiplier is 0.1, gold)|
|68 =||68R (multiplier is 1, black)|
Later additions were “G” (from the SI's “giga-”), and “T” (from the SI's “tera-”). Notice the code is all in uppercase (a different set of characters, in lowercase is used with capacitors).
Finally, most recently, an uppercase “L” was chosen to represent the submultiplier 1/1000th (SI's “milli-”). For example, 6L8 Ω is 6.8 milliohms.
IEC 60062:2016. Marking codes for resistors and capacitors.
IEC 60062:2016/COR1:2016. CORRIGENDUM 1.
IEC 60062:2016/AMD1:2019. Amendment 1 - Marking codes for resistors and capacitors.
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Last revised: 10 October 2019.