ASTM E1594-99

Standard Guide for Expression of Temperature

SCOPE
1.1 This guide covers uniform methods for expressing temperature, temperature values, and temperature differences.
1.2 This guide is intended as a supplement to Practice E380.

General Information

• Status: Historical
• Publication Date: 09-Nov-1999
• ICS: 17.200.20 - Temperature-measuring instruments
• Technical Committee: E20 - Temperature Measurement
• Drafting Committee: E20.91 - Editorial and Terminology

Relations

• Replaced By: ASTM E1594-06 - Standard Guide for Expression of Temperature
• Effective Date: 01-Nov-2006
• Referred By: ASTM E220-19 - Standard Test Method for Calibration of Thermocouples By Comparison Techniques
• Effective Date: 10-Nov-1999
• Referred By: ASTM E563-22 - Standard Practice for Preparation and Use of an Ice-Point Bath as a Reference Temperature
• Effective Date: 10-Nov-1999
• Referred By: ASTM E344-20 - Terminology Relating to Thermometry and Hydrometry
• Effective Date: 10-Nov-1999
• Referred By: ASTM E1750-10(2016) - Standard Guide for Use of Water Triple Point Cells
• Effective Date: 10-Nov-1999

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:E1594–99
Standard Guide for
Expression of Temperature
This standard is issued under the fixed designation E1594; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope referable is the Kelvin Thermodynamic Temperature Scale
(KTTS). A value of temperature expressed on the KTTS is
1.1 This guide covers uniform methods for expressing
known as a thermodynamic temperature, symbol T.
temperature, temperature values, and temperature differences.
5.1.2 The unit of thermodynamic temperature is the kelvin,
1.2 This guide is intended as a supplement to IEEE/ASTM
symbolK.ThekelvinisabaseunitintheInternationalSystem
SI-10.
of Units (SI).
2. Referenced Documents
NOTE 1—The symbol for the kelvin is the capital letter K only; the
2.1 ASTM Standards:
degree sign (°) is not used.
E344 Terminology Relating to Thermometry and Hydrom-
5.1.3 The expression of a value of thermodynamic tempera-
etry
ture is written:
IEEE/ASTM SI-10 Standard for Use of the International
3 T 5 n K (1)
k
System of Units (SI): The Modern Metric System
where:
3. Terminology
n 5 a numerical value designating the magnitude,
k
3.1 General—Standard terms used in this guide are defined
K 5 the symbol for the unit kelvin.
in Terminology E344 and in IEEE/ASTM SI-10.
The magnitude may also be represented by the notation T/K.
5.1.4 Athermodynamic temperature may be expressed as a
4. Basic Concepts
Celsius temperature. The symbol t is to be used to designate a
4.1 Temperature is a fundamental measurable quantity des-
Celsius temperature, but if this symbol leads to a conflict in
ignated by the symbol T or the symbol t (see 5.1). In
notation in a given context, it is acceptable to use the symbol
expressions of dimensions the symbol u is sometimes used to
T instead to designate a Celsius temperature.
indicate the dimension temperature.
5.1.5 The unit of Celsius temperature is the degree Celsius,
4.2 Atemperature value is expressed in terms of a tempera-
symbol °C. The degree Celsius is a derived SI unit.
ture scale. The complete description consists of a numerical
NOTE 2—The symbol for the degree Celsius consists of the degree sign
value designating the magnitude, a unit, and, where appropri-
(°) followed by the capital letter C. Neither the degree sign nor the letter
ate, a tolerance or uncertainty. Both the numerical value and
C alone represents the degree Celsius.
unit depend upon the scale.
5.1.6 The expression of a value of Celsius temperature is
4.3 Aunit of temperature is understood to mean an interval
written:
on a temperature scale.
4.4 A temperature difference, interval, or increment is also
t 5 n °C (2)
c
described by a numerical value designating the magnitude, a
where:
unit, and, where appropriate, a tolerance or uncertainty.
n 5 a numerical value designating the magnitude,
c
°C 5 the symbol for the unit degree Celsius.
5. Temperature Scales
The magnitude may also be represented by the notation t/°C.
5.1 Thermodynamic Temperature Scales:
5.1.7 Bydefinition,atanytemperature,atemperatureincre-
5.1.1 By international agreement, the theoretical tempera-
mentofonedegreeCelsiusisequaltoatemperatureincrement
ture scale to which all temperature values should be ultimately
of one kelvin.
5.1.8 By definition, the Celsius temperature t 50°Cisthe
This guide is under the jurisdiction ofASTM Committee E-20 on Temperature same as the thermodynamic temperature T 5273.15 K. The
Measurement and is the direct responsibility of Subcommittee E20.91 on Editorial
relationbetweennumericalvaluesassociatedwithbothexpres-
and Terminology.
sions of a temperature is therefore given by:
Current edition approved Nov. 10, 1999. Published January 2000. Originally
published as E 1594–94. Last previous edition E 1594–94.
n 5 n 2273.15 (3)
c k
Annual Book of ASTM Standards, Vol 14.03.
Annual Book of ASTM Standards, Vol 14.02.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E1594
6.3.3 Multipleandsubmultipleprefixesshouldnotnormally
where:
be used with the unit for the expression of values of tempera-
t 5 n °C is the same temperature as T 5 n K.
c k
ture.
5.2 Practical Temperature Scales:
5.2.1 Practical temperature scales have been established by 6.3.4 When a tolerance or uncertainty is associated with a
international agreement for the practice of temperature mea- value of temperature, both the value and the tolerance or
surement;amongthemaretheInternationalPracticalTempera- uncertainty should be expressed with the same unit. Unit
prefixes should not normally be used. The unit symbol should
ture Scale of 1968, the International Practical Temperature
Scale of 1948, and the International Temperature Scale of follow each numerical value. For example:
1927.
t 560.0°C 61.5°C (4)
5.2.2 The practical temperature scale now in use, supersed-
T 5273.150K 60.001K (5)
ing all others, is the International Temperature Scale of 1990.
Itisdefinedsothatanumericalvalueoftemperatureexpressed
7. Expression of Temperature Differences, Intervals, and
on the scale is close to the numerical value of thermodynamic
Increments
temperature.
5.2.3 A value of temperature on a practical temperature 7.1 Temperature differences, intervals, and increments are
normally understood to be expressed with reference to the
scale may be expressed either in kelvins or in degrees Celsius
same temperature scale as are values of temperature, within a
using the designations, symbols, and relations given in 5.1.
given context. Where there is a possibility of misunderstand-
ing, the temperature scale should be explicitly identified.
6. Expression of Values of Temperature
7.2 A small temperature difference, interval, or increment
6.1 Temperature Scale Identification:
may be expressed in terms of a submultiple of the appropriate
6.1.1 It is important that the temperature scale upon which
unit of temperature. The use of unit prefixes to indicate
values
...