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

capacitance Capacitance is the ability of an object 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 are two closely related ...

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 A resistor is a passive two-terminal electronic component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active e ...

and

capacitor In electrical engineering, a capacitor is a device that stores electrical energy by accumulating electric charges on two closely spaced surfaces that are insulated from each other. The capacitor was originally known as the condenser, a term st ...

values defined in the international standard IEC 60062 (formerly IEC 62) since 1952. Other standards including DIN 40825 (1973), BS 1852 (1975), IS 8186 (1976), and EN 60062 (1993) have also accepted it. 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 Electrical engineering is an engineering discipline concerned with the study, design, and application of equipment, devices, and systems that use electricity, electronics, and electromagnetism. It emerged as an identifiable occupation in the l ...

to denote the values of resistors and capacitors in

circuit diagram A circuit diagram (or: wiring diagram, electrical diagram, elementary diagram, electronic schematic) is a graphical representation of an Electrical network, electrical circuit. A pictorial circuit diagram uses simple images of components, whil ...

s and in the production of

electronic circuit An electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or Conductive trace, traces through which electric current can flow. It is a t ...

s (for example in bills of material and in silk screens). This method avoids overlooking the

decimal separator FIle:Decimal separators.svg, alt=Four types of separating decimals: a) 1,234.56. b) 1.234,56. c) 1'234,56. d) ١٬٢٣٤٫٥٦., Both a comma and a full stop (or period) are generally accepted decimal separators for international use. The apost ...

, 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 Ohm (symbol Ω) is a unit of electrical resistance named after Georg Ohm. Ohm or OHM may also refer to: People * Georg Ohm (1789–1854), German physicist and namesake of the term ''ohm'' * Germán Ohm (born 1936), Mexican boxer * Jörg Ohm (1 ...

farad The farad (symbol: F) is the unit of electrical capacitance, the ability of a body to store an electrical charge, in the International System of Units, International System of Units (SI), equivalent to 1 coulomb per volt (C/V). It is named afte ...

) 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 photocopying printed circuit diagrams. Another advantage is the easier sortability of values which helps to optimize the

bill of materials A bill of materials or product structure (sometimes bill of material, BOM or associated list) is a list of the raw materials, sub-assemblies, intermediate assemblies, sub-components, parts, and the quantities of each needed to manufacture an Prod ...

by combining similar part values to improve maintainability and reduce costs. The code letters are loosely related to the corresponding

SI prefix The International System of Units, internationally known by the abbreviation SI (from French ), is the modern form of the metric system and the world's most widely used system of measurement. It is the only system of measurement with official st ...

, 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 or F is used instead of the decimal separator. For example, 1R2 indicates , and 18R indicates . 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 graphical character (computing), characters, especially the written characters of human language, allowing them to be stored, transmitted, and transformed using computers. The numerical v ...

s (though it is present in the now-ubiquitous

Unicode Unicode or ''The Unicode Standard'' or TUS is a character encoding standard maintained by the Unicode Consortium designed to support the use of text in all of the world's writing systems that can be digitized. Version 16.0 defines 154,998 Char ...

) 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 ( ), memory trick or memory device is any learning technique that aids information retention or retrieval in the human memory, often by associating the information with something that is easier to remember. It makes use of e ...

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 (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

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

. 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 (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, also known as the Roman alphabet, is the collection of letters originally used by the Ancient Rome, ancient Romans to write the Latin language. Largely unaltered except several letters splitting—i.e. from , and from � ...

is available. Several manufacturers of resistors utilize the RKM code as part of the components' manufacturer's part numbers (MPNs).

Similar codes

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

inductor An inductor, also called a coil, choke, or reactor, is a Passivity (engineering), passive two-terminal electronic component, electrical component that stores energy in a magnetic field when an electric current flows through it. An inductor typic ...

s with R indicating the decimal point in microhenry (e.g. 4R7 for ). A similar non-standard notation using the unit symbol instead of a decimal separator is sometimes used to indicate

voltage Voltage, also known as (electrical) potential difference, electric pressure, or electric tension, is the difference in electric potential between two points. In a Electrostatics, static electric field, it corresponds to the Work (electrical), ...

s (i.e. 0V8 for , 1V8 for , 3V3 for or 5V0 for ) in contexts where a decimal separator would be impossible to use or inappropriate (e.g. in signal or pin names, in variable names, in file names, or in

label A label (as distinct from signage) is a piece of paper, plastic film, cloth, metal, or other material affixed to a container or product. Labels are most often affixed to packaging and containers using an adhesive, or sewing when affix ...

s or subscripts). Alternatively, letter P (presumably standing for "positive voltage" or "power supply rail") is seen being used instead of the V sometimes in device models and netnames (i.e. 1P8 for , 3P3 for ). Respectively, both variants are also used as part of the MPN codes of zener diodes and

voltage regulator A voltage regulator is a system designed to automatically maintain a constant voltage. It may use a simple feed-forward design or may include negative feedback. It may use an electromechanical mechanism or electronic components. Depending on the ...

s by some manufacturers.

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 (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 Depar ...

Specifications (JAN) since the mid-1940s.

Temperature coefficient code

Letter codes for the temperature coefficient of resistance (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 * DIN EN 60062:2017-06 * DIN EN 60062:2020-03 * 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, JIS C 60062 * TGL 31667

Notes

References

{{List of IEC standards Standards Electrical components Encodings