The RKM code, also referred to as "letter and numeral code for resistance and

capacitance Capacitance is the capability of a material object or device to store electric charge. It is measured by the change in charge in response to a difference in electric potential, expressed as the ratio of those quantities. Commonly recognized ar ...

values and tolerances", "letter and digit code for resistance and capacitance values and tolerances", or informally as "R notation" is a notation to specify resistor and

capacitor A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals. The effect of ...

values defined in the international standard IEC 60062 (formerly IEC 62) since 1952. It is also adopted by various other standards including DIN 40825 (1973), BS 1852 (1975), IS 8186 (1976) and EN 60062 (1993). The updated IEC 60062:2016, amended in 2019, comprises the most recent release of the standard.

Overview

Originally meant also as part marking code, this shorthand notation is widely used in electrical engineering to denote the values of resistors and capacitors in

circuit diagram A circuit diagram (wiring diagram, electrical diagram, elementary diagram, electronic schematic) is a graphical representation of an electrical circuit. A pictorial circuit diagram uses simple images of components, while a schematic diagram s ...

s and in the production of electronic circuits (for example in bills of material and in

silk screen Screen printing is a printing technique where a mesh is used to transfer ink (or dye) onto a substrate, except in areas made impermeable to the ink by a blocking stencil. A blade or squeegee is moved across the screen to fill the open me ...

s). This method avoids overlooking the

decimal separator A decimal separator is a symbol used to separate the integer part from the fractional part of a number written in decimal form (e.g., "." in 12.45). Different countries officially designate different symbols for use as the separator. The choi ...

, which may not be rendered reliably on components or when duplicating documents. The standards also define a '' color code for fixed resistors''.

Part value code

For brevity, the notation omits to always specify the unit ( ohm or farad) explicitly and instead relies on implicit knowledge raised from the usage of specific letters either only for resistors or for capacitors, the case used (uppercase letters are typically used for resistors, lowercase letters for capacitors), a part's appearance, and the context. The notation also avoids using a

and replaces it by a letter associated with the prefix symbol for the particular value. This is not only for brevity (for example when printed on the part or PCB), but also to circumvent the problem that decimal separators tend to "disappear" when

photocopy A photocopier (also called copier or copy machine, and formerly Xerox machine, the generic trademark) is a machine that makes copies of documents and other visual images onto paper or plastic film quickly and cheaply. Most modern photocopiers ...

ing printed circuit diagrams. The code letters are loosely related to the corresponding SI prefix, but there are several exceptions, where the capitalization differs or alternative letters are used. For example, 8K2 indicates a resistor value of 8.2 kΩ. Additional zeros imply tighter tolerance, for example 15M0. When the value can be expressed without the need for a prefix, an "R" is used instead of the decimal separator. For example, 1R2 indicates 1.2 Ω, and 18R indicates 18 Ω. For ''resistances'', the standard dictates the use of the uppercase letters L (for 10⁻³), R (for 10⁰ = 1), K (for 10³), M (for 10⁶), and G (for 10⁹) to be used instead of the decimal point. The usage of the letter R instead of the SI unit symbol Ω for ohms stems from the fact that the Greek letter Ω is absent from most older

character encoding Character encoding is the process of assigning numbers to Graphics, graphical character (computing), characters, especially the written characters of Language, human language, allowing them to be Data storage, stored, Data communication, transmi ...

s (though it is present in the now-ubiquitous

Unicode Unicode, formally The Unicode Standard,The formal version reference is is an information technology standard for the consistent encoding, representation, and handling of text expressed in most of the world's writing systems. The standard, wh ...

) and therefore is sometimes impossible to reproduce, in particular in some CAD/CAM environments. The letter R was chosen because visually it loosely resembles the Ω glyph, and also because it works nicely as a

mnemonic A mnemonic ( ) device, or memory device, is any learning technique that aids information retention or retrieval (remembering) in the human memory for better understanding. Mnemonics make use of elaborative encoding, retrieval cues, and imag ...

for ''r''esistance in many languages. The letters G and T weren't part of the first issue of the standard, which pre-dates the introduction of the

SI system The International System of Units, known by the international abbreviation SI in all languages and sometimes pleonastically as the SI system, is the modern form of the metric system and the world's most widely used system of measurement. E ...

(hence the name "RKM code"), but were added after the adoption of the corresponding SI prefixes. The introduction of the letter L in more recent issues of the standard (instead of an SI prefix m for

milli ''Milli'' (symbol m) is a unit prefix in the metric system denoting a factor of one thousandth (10−3). Proposed in 1793, and adopted in 1795, the prefix comes from the Latin , meaning ''one thousand'' (the Latin plural is ). Since 1960, the pre ...

) is justified to maintain the rule of only using uppercase letters for resistances (the otherwise resulting M was already in use for

mega Mega or MEGA may refer to: Science * mega-, a metric prefix denoting 106 * Mega (number), a certain very large integer in Steinhaus–Moser notation * "mega-" a prefix meaning "large" that is used in taxonomy * Gravity assist, for ''Moon-Eart ...

). Similar, the standard prescribes the following lowercase letters for ''capacitances'' to be used instead of the decimal point: p (for 10⁻¹²), n (for 10⁻⁹), µ (for 10⁻⁶), m (for 10⁻³), but uppercase F (for 10⁰ = 1) for farad. The letters p and n weren't part of the first issue of the standard, but were added after the adoption of the corresponding SI prefixes. In cases where the Greek letter µ is not available, the standard allows it to be replaced by u (or U, when only uppercase letters are available). This usage of u instead of µ is also in line with ISO 2955 (1974, 1983), DIN 66030 (Vornorm 1973; 1980, 2002), BS 6430 (1983) and

Health Level 7 Health Level Seven or HL7 refers to a set of international standards for transfer of clinical and administrative data between software applications used by various healthcare providers. These standards focus on the application layer, which is "la ...

(HL7), which allow the prefix μ to be substituted by the letter u (or U) in circumstances in which only the

Latin alphabet The Latin alphabet or Roman alphabet is the collection of letters originally used by the ancient Romans to write the Latin language. Largely unaltered with the exception of extensions (such as diacritics), it used to write English and th ...

is available.

Similar codes

Though non-standardized some manufacturers use the RKM code also to mark

inductor An inductor, also called a coil, choke, or reactor, is a passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it. An inductor typically consists of an insulated wire wound into a c ...

s with "R" marking the decimal point in microhenry (e.g. 4R7 for 4.7 μH). A similar not standardized notation using the unit symbol instead of a decimal separator is sometimes used to indicate

voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to ...

s (3V3 for 3.3 V, or 1V8 for 1.8 V) in contexts where a decimal separator would be inappropriate (e.g. in signal names or

file name A filename or file name is a name used to uniquely identify a computer file in a directory structure. Different file systems impose different restrictions on filename lengths. A filename may (depending on the file system) include: * name &ndas ...

s).

Tolerance code

Letter code for resistance and capacitance tolerances: Before the introduction of the RKM code, some of the letters for symmetrical tolerances (viz. G, J, K, M) were already used in US military contexts following the

American War Standard American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...

(AWS) and

Joint Army-Navy The Joint Electronics Type Designation System (JETDS), which was previously known as the Joint Army-Navy Nomenclature System (AN System. JAN) and the Joint Communications-Electronics Nomenclature System, is a method developed by the U.S. War Depa ...

Specifications (JAN) since the mid-1940s.

Temperature coefficient code

Letter codes for the

temperature coefficient of resistance A temperature coefficient describes the relative change of a physical property that is associated with a given change in temperature. For a property ''R'' that changes when the temperature changes by ''dT'', the temperature coefficient α is def ...

(TCR):

Production date codes

Twenty-year cycle code

* First character: Year of production in twenty-year cycle ** A = 2030, 2010, 1990, 1970 ** B = 2031, 2011, 1991, 1971 ** C = 2032, 2012, 1992, 1972 ** D = 2033, 2013, 1993, 1973 ** E = 2034, 2014, 1994, 1974 ** F = 2035, 2015, 1995, 1975 ** H = 2036, 2016, 1996, 1976 ** J = 2037, 2017, 1997, 1977 ** K = 2038, 2018, 1998, 1978 ** L = 2039, 2019, 1999, 1979 ** M = 2020, 2000, 1980 ** N = 2021, 2001, 1981 ** P = 2022, 2002, 1982 ** R = 2023, 2003, 1983 ** S = 2024, 2004, 1984 ** T = 2025, 2005, 1985 ** U = 2026, 2006, 1986 ** V = 2027, 2007, 1987 ** W = 2028, 2008, 1988 ** X = 2029, 2009, 1989 * Second character: Month of production ** 1 to 9 = January to September ** O = October ** N = November ** D = December Example: J8 = August 2017 (or August 1997) Some manufacturers also used the production date code as a stand-alone code to indicate the production date of integrated circuits. Some manufacturers specify a three-character date code with a two-digit week number following the year letter. IEC 60062 also specifies a four-character year/week code.

Ten-year cycle code

* First character: Year of production in ten-year cycle ** 0 = 2020 ** 1 = 2021 ** 2 = 2022, 2012 ** 3 = 2023, 2013 ** 4 = 2024, 2014 ** 5 = 2025, 2015 ** 6 = 2026, 2016 ** 7 = 2017 ** 8 = 2018 ** 9 = 2019 * Second character: Month of production ** 1 to 9 = January to September ** X = October ** Y = November ** Z = December Example: 78 = August 2017 IEC 60062 also specifies a four-character year/week code.

Four-year cycle code

IEC 60062 also specifies a single-character four-year cycle year/month code.

Marking codes for E series preferred values

Three-character resistor marking code

For resistances following the ( E48 or) E96 series of preferred values, the former EIA-96 as well as IEC 60062:2016 define a '' special three-character marking code for resistors'' to be used on small parts. The code consists of two digits denoting one of the "positions" in the series of E96 values followed by a letter indicating the multiplier.

Two-character capacitor marking code

For capacitances following the ( E3, E6, E12 or) E24 series of preferred values, the former ANSI/EIA-198-D:1991, ANSI/EIA-198-1-E:1998 and ANSI/EIA-198-1-F:2002 as well as the amendment IEC 60062:2016/AMD1:2019 to IEC 60062 define a '' special two-character marking code for capacitors'' for very small parts which leave no room to print any longer codes onto them. The code consists of an uppercase letter denoting the two significant digits of the value followed by a digit indicating the multiplier. The EIA standard also defines a number of lowercase letters to specify a number of values not found in E24.

Corresponding standards

* IEC 62:1952 (aka IEC 60062:1952), first edition, 1952-01-01 * IEC 62:1968 (aka IEC 60062:1968), second edition, 1968-01-01 * IEC 62:1968/AMD1:1968 (aka IEC 60062:1968/AMD1:1968), amended second edition, 1968-12-31 * IEC 62:1974 (aka IEC 60062:1974) * IEC 62:1974/AMD1:1988 (aka IEC 60062:1974/AMD1:1988), amended third edition, 1988-04-30 * IEC 62:1974/AMD2:1989 (aka IEC 60062:1974/AMD2:1989), amended third edition, 1989-01-01 * IEC 62:1992 (aka IEC 60062:1992), fourth edition, 1992-03-15 * IEC 62:1992/AMD1:1995 (aka IEC 60062:1992/AMD1:1995), amended fourth edition, 1995-06-19 * IEC 60062:2004 (fifth edition, 2004-11-08) * IEC 60062:2016 (sixth edition, 2016-07-12) * IEC 60062:2016/COR1:2016 (corrected sixth edition, 2016-12-05) * IEC 60062:2016/AMD1:2019 (amendment 1, 2019-08-20) * IEC 60062:2016+AMD1:2019 CSV (consolidated version 6.1, 2019-08-20) * EN 60062:1993 * EN 60062:1994 (1994-10) * EN 60062:2005 * EN 60062:2016 * EN 60062:2016/AC:2016-12 (corrected edition) * EN 60062:2016/A1:2019 (amendment 1) * BS 1852:1975 (related to IEC 60062:1974) * BS EN 60062:1994 * BS EN 60062:2005 * BS EN 60062:2016 * DIN 40825:1973-04 (capacitor/resistor value code), DIN 41314:1975-12 (date code) * DIN IEC 62:1985-12 (aka DIN IEC 60062:1985-12) * DIN IEC 62:1989-10 (aka DIN IEC 60062:1989-10) * DIN IEC 62:1990-11 (aka DIN IEC 60062:1990-11) * DIN IEC 62:1993-03 (aka DIN IEC 60062:1993-03) * DIN EN 60062:1997-09 * DIN EN 60062:2001-11 * DIN EN 60062:2005-11 * ČSN EN 60062 * DS/EN 60062 * EVS-EN 60062 * (GOST) ГОСТ IEC 60062-2014 (related to IEC 60062-2004) * ILNAS-EN 60062 * I.S. EN 60062 * NEN EN IEC 60062 * NF EN 60062 * ÖVE/ÖNORM EN 60062 * PN-EN 60062 * prМКС EN 60062 * SN EN 60062 * TS 2932 EN 60062 * UNE-EN 60062 * BIS IS 4114-1967 * IS 8186-1976 (related to IEC 62:1974) * JIS C 5062 * TGL 31667

Notes

References

{{List of IEC standards Standards