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 are ...
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 electrical 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 el ...
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 a ...
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
Electrical engineering is an engineering discipline concerned with the study, design, and application of equipment, devices, and systems which use electricity, electronics, and electromagnetism. It emerged as an identifiable occupation in the ...
to denote the values of resistors and capacitors in
circuit diagrams 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 ch ...
, 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
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 (SI). It is named after the English physicist Michael Faraday (1791–1867). In SI base unit ...
) 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
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 ch ...
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
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 ...
, 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 10
0 = 1),
K
(for 10
3),
M
(for 10
6), and
G
(for 10
9) 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 characters, especially the written characters of human language, allowing them to be stored, transmitted, and transformed using digital computers. The numerical values tha ...
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, w ...
) 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 imager ...
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
SI prefix
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 ...
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).
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 10
0 = 1) for
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 (SI). It is named after the English physicist Michael Faraday (1791–1867). In SI base unit ...
.
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
ISO is the most common abbreviation for the International Organization for Standardization.
ISO or Iso may also refer to: Business and finance
* Iso (supermarket), a chain of Danish supermarkets incorporated into the SuperBest chain in 2007
* Is ...
(1974,
1983
),
DIN 66030
DIN or Din or din may refer to:
People and language
* Din (name), people with the name
* Dīn, an Arabic word with three general senses: judgment, custom, and religion from which the name originates
* Dinka language (ISO 639 code: din), spoken by ...
(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 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
The henry (symbol: H) is the unit of electrical inductance in the International System of Units (SI). If a current of 1 ampere flowing through a coil produces flux linkage of 1 weber turn, that coil has a self inductance of 1 henry. The unit ...
(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 &nda ...
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 (AWS) and
Joint Army-Navy 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
* 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
See also
*
Electronic color code
An electronic color code or electronic colour code (see spelling differences) is used to indicate the values or ratings of electronic components, usually for resistors, but also for capacitors, inductors, diodes and others. A separate code, the ...
*
SI prefix
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 ...
*
Metric prefix
A metric prefix is a unit prefix that precedes a basic unit of measure to indicate a multiple or submultiple of the unit. All metric prefixes used today are decadic. Each prefix has a unique symbol that is prepended to any unit symbol. The pr ...
*
Engineering notation
Engineering notation or engineering form (also technical notation) is a version of scientific notation in which the exponent of ten must be divisible by three (i.e., they are powers of a thousand, but written as, for example, 106 instead of 1000 ...
*
E notation
*
Cifrão (a similar scheme for a currency)
*
Fermata
A fermata (; "from ''fermare'', to stay, or stop"; also known as a hold, pause, colloquially a birdseye or cyclops eye, or as a grand pause when placed on a note or a rest) is a symbol of musical notation indicating that the note should be ...
(a remotely similar musical notation)
Notes
References
{{List of IEC standards
Standards