1、Designation: E1594 11Standard Guide forExpression of Temperature1This standard is issued under the fixed designation E1594; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicate
2、s the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This guide covers uniform methods for expressingtemperature, temperature values, and temperature differences.1.2 This guide is intended as a supplement to IEEE/ASTMS
3、I-10.2. Referenced Documents2.1 ASTM Standards:2E344 Terminology Relating to Thermometry and Hydrom-etryIEEE/ASTM SI-10 Standard for Use of the InternationalSystem of Units (SI): The Modern Metric System3. Terminology3.1 GeneralStandard terms used in this guide are definedin Terminology E344 and in
4、IEEE/ASTM SI-10.4. Basic Concepts4.1 Temperature is a fundamental measurable quantity des-ignated by the symbol T or the symbol t (see 5.1). Inexpressions of dimensions the symbol u is sometimes used toindicate the dimension temperature.4.2 A temperature value is expressed in terms of a tempera-ture
5、 scale. The complete description consists of a numericalvalue designating the magnitude, a unit, and, where appropri-ate, a tolerance or uncertainty. Both the numerical value andthe unit depend upon the scale.4.3 A unit of temperature is understood to mean an intervalon a temperature scale.4.4 A tem
6、perature difference, interval, or increment is alsodescribed by a numerical value designating the magnitude, aunit, and, where appropriate, a tolerance or uncertainty.5. Temperature Scales5.1 Thermodynamic Temperature Scales:5.1.1 By international agreement, the theoretical tempera-ture scale to whi
7、ch all temperature values should be ultimatelyreferable is the Kelvin Thermodynamic Temperature Scale(KTTS). A value of temperature expressed on the KTTS isknown as a thermodynamic temperature, symbol T.5.1.2 The unit of thermodynamic temperature is the kelvin,symbol K. The kelvin is a base unit in
8、the International Systemof Units (SI). Note that the symbol for the kelvin is the capitalletter K only; the degree sign () is not used.5.1.3 The expression of a value of thermodynamic tempera-ture is written:T 5 nkK (1)where:nk= a numerical value designating the magnitude,K = the symbol for the unit
9、 kelvin.The magnitude may also be represented by the notation T/K.5.1.4 A thermodynamic temperature may be expressed as aCelsius temperature. The symbol t is to be used to designate aCelsius temperature, but if this symbol leads to a conflict innotation in a given context, it is acceptable to use th
10、e symbolT instead to designate a Celsius temperature.5.1.5 The unit of Celsius temperature is the degree Celsius,symbol C. The degree Celsius is a derived SI unit. Note thatthe symbol for the degree Celsius consists of the degree sign ()followed by the capital letter C. Neither the degree sign nor t
11、heletter C alone represents the degree Celsius.5.1.6 The expression of a value of Celsius temperature iswritten:t 5 ncC (2)where:nc= a numerical value designating the magnitude,C = the symbol for the unit degree Celsius.The magnitude may also be represented by the notation t/C.5.1.7 By definition, a
12、t any temperature, a temperature incre-ment of one degree Celsius is equal to a temperature incrementof one kelvin.5.1.8 By definition, the Celsius temperature t = 0 C is thesame as the thermodynamic temperature T = 273.15 K. Therelation between numerical values associated with both expres-sions of
13、a temperature is therefore given by:nc5 nk2 273.15 (3)1This guide is under the jurisdiction of ASTM Committee E20 on TemperatureMeasurement and is the direct responsibility of Subcommittee E20.91 on Editorialand Terminology.Current edition approved Nov. 1, 2011. Published December 2011. Originallyap
14、proved in 1994. Last previous edition approved in 2006 as E1594 06. DOI:10.1520/E1594-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summ
15、ary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.where:t = ncC is the same temperature as T = nkK.5.2 Practical Temperature Scales:5.2.1 Practical temperature scales have been established byinternational ag
16、reement for the practice of temperature mea-surement. Among them are the International Practical Tem-perature Scale of 1968, the International Practical TemperatureScale of 1948, and the International Temperature Scale of1927.35.2.2 Practical scales are designed so that a numerical valueof temperatu
17、re expressed on the scale is close to the numericalvalue of thermodynamic temperature. Because the KTTS isdifficult to implement, the vast majority of temperature mea-surements are based on a practical scale.5.2.3 There are two practical temperature scales now in use,superseding all others. The Inte
18、rnational Temperature Scale of19904defines temperatures above 0.65 K. The ProvisionalLow-Temperature Scale from 0.9 mK to 1 K5defines tempera-tures between 0.0009 K and 1 K.5.2.4 A value of temperature on a practical temperaturescale may be expressed either in kelvins or in degrees Celsiususing the
19、designations, symbols, and relations given in 5.1.6. Expression of Values of Temperature6.1 Temperature Scale Identification:6.1.1 It is important that the temperature scale upon whichvalues of temperature are expressed be identified in a docu-ment. When reference to more than one scale is made in a
20、document, or when critical data are presented, scale identifi-cation is essential.6.1.2 Thermodynamic temperatures may be identified assuch, or with reference to the KTTS. If values of temperatureare expressed on a practical temperature scale, the scale shouldbe identified. The identification may be
21、 an abbreviation, asdefined in the text of the scale; for example, the InternationalTemperature Scale of 1990 is abbreviated ITS-90 and theProvisional Low-Temperature Scale from 0.9 mK to1Kisabbreviated PLTS-2000.6.1.3 Scale identification may be placed in text, in foot-notes, in table headings, or
22、in figures, as appropriate.6.1.4 A scale may also be identified by a subscript associ-ated with a quantity symbol; for example, TThand tThforthermodynamic temperatures, T90and t90for temperaturevalues on ITS-90, and T2000for temperature values on PLTS-2000.6.2 Numerical Format:6.2.1 Numerical values
23、 of temperature should be expressedas decimal numbers.6.3 Unit Symbol Format:6.3.1 The unit symbol should be separated from the numeri-cal value by a single space. There should be no space betweenthe degree sign and the letter C. Punctuation is not part of theunit symbol; only punctuation required b
24、y context or grammarshould follow the unit symbol.6.3.2 In an expression of a range of temperature values, thesame unit symbol should be used with each value in the range;for example: “over the temperature range 16 K to 50 K” or“any temperature between 20 C and 30 C.”6.3.3 Multiple and submultiple p
25、refixes should not normallybe used with the unit for the expression of values of tempera-ture, for temperatures above 1 K. For temperatures below 1 K,a submultiple may be used. The preferred submultiple is 0.001(prefix “milli,” symbol m).6.3.4 When a tolerance or uncertainty is associated with avalu
26、e of temperature, both the value and the tolerance oruncertainty should be expressed with the same unit. Unitprefixes should not normally be used. The unit symbol shouldfollow each numerical value. For example:t905 60.0 C 6 1.5 C (4)T905 273.150 K 6 0.001 K (5)6.3.5 When a tolerance or uncertainty i
27、s presented in aformat not directly associated with a value of temperature, aunit prefix may be used. The preferred submultiple is 0.001(prefix “milli,” symbol m). For example, the uncertainty u of atemperature value may be expressed:ut90! 5 0.7 mK (6)7. Expression of Temperature Differences, Interv
28、als, andIncrements7.1 Temperature differences, intervals, and increments arenormally understood to be expressed with reference to thesame temperature scale as are values of temperature, within agiven context. Where there is a possibility of misunderstand-ing, the temperature scale should be explicit
29、ly identified.7.2 A small temperature difference, interval, or incrementmay be expressed in terms of a submultiple of the appropriateunit of temperature. The use of unit prefixes to indicatesubmultiples should follow the guidelines in IEEE/ASTMSI-10. The preferred submultiple is 0.001 (prefix “milli
30、,”symbol m).7.3 The magnitude of a temperature increment at a particu-lar temperature is sometimes expressed as a relative fraction ora percentage of the numerical value (on a particular tempera-ture scale) of the temperature. Such usage should be carefullyexplained so that the expression is meaning
31、ful and unambigu-ous.7.4 When a tolerance or uncertainty is associated with themagnitude of a temperature difference, interval, or increment,both the magnitude and tolerance or uncertainty should beexpressed in the same numerical format and with the same unit.An appropriate unit prefix may be used (
32、see 7.2). The resultingunit symbol should follow each numerical value in the expres-sion. For example:Dt 5 10.00 C 6 0.01 C describes a temperature interval ofabout 10 C (7)3Evolution of the International Practical Temperature Scale of 1968, ASTM STP565, ASTM, 1974.4Preston-Thomas, H., “The Internat
33、ional Temperature Scale of 1990 (ITS-90),”Metrologia, Vol 27, No. 1, 1990, pp. 310. For errata see ibid, Vol 27, No. 2, 1990,p. 107.5Rusby, R. L., Durieux, M., Reesink, A. L, Hudson, R. P., Schuster, G., Khne,M., Fogle, W. E., Soulen, R. J., and Adams, E. D., “The Provisional LowTemperature Scale fr
34、om 0.9 mK to 1 K, PLTS-2000.” J. Low Temp. Physics Vol 126,2002, pp. 633642.E1594 112DT 5 9.8 mK 6 0.2 mK describes a temperature interval ofabout 9.8 mK (8)7.5 In the expression of derived quantities the unit oftemperature should be the kelvin. For example, the preferredexpression for heat capacity
35、 is joules per kelvin, JK1or J/K;for temperature gradient, kelvins per metre, Km1or K/m.8. Units Other Than SI8.1 Values of temperature are sometimes expressed in de-grees Rankine, symbol R, instead of kelvins, or in degreesFahrenheit, symbol F, instead of degrees Celsius. Neither thedegree Rankine
36、nor the degree Fahrenheit are part of the SI.8.2 At any temperature, a temperature increment of onedegree Rankine is equal to a temperature increment of 5/9kelvin. The relation between numerical values associated withboth expressions of a temperature is given by:nr5 9nk /5 (9)where:T = nrR is the sa
37、me temperature as T=nkK.8.3 At any temperature, a temperature increment of onedegree Fahrenheit is equal to a temperature increment of 5/9degree Celsius. The relation between numerical values associ-ated with both expressions of a temperature is given by:nf5 9nc /5 1 32 (10)where:t = nfF is the same
38、 temperature as t=ncC.8.4 From the relations in 5.1, 8.2, and 8.3, it follows that:8.4.1 At any temperature, a temperature increment of onedegree Rankine is equal to a temperature increment of onedegree Fahrenheit.8.4.2 If T=nrR and t = nfF are the same temperature,then the relation between the nume
39、rical values is given by:nr5 nf1 459.67 (11)8.4.3 If a temperature interval expressed in degrees Rankineor degrees Fahrenheit has a magnitude n1, and the sametemperature interval expressed in kelvins or degrees Celsiushas a magnitude n2, then the relation between n1and n2is givenby:n15 9n2 /5 (12)8.
40、5 Both thermodynamic temperatures and values of tem-perature on a practical temperature scale may be expressed indegrees Rankine or degrees Fahrenheit. In both cases theconsiderations of Section 6 apply.8.6 The use of multiple or submultiple prefixes with thedegree Rankine or the degree Fahrenheit i
41、s not recommended.9. Keywords9.1 degree Celsius; degree Fahrenheit; degree Rankine;kelvin; SI; temperature; temperature difference; temperatureincrement; temperature interval; temperature scales; tempera-ture value; thermodynamic temperatureASTM International takes no position respecting the validit
42、y of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject
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44、s. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard i
45、s copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).E1594 113
