ASTM_F_2362_-_03_2013.pdf

Designation:F236203(Reapproved 2013)An American National StandardStandard Specification forTemperature Monitoring Equipment1This standard is issued under the fixed designation F2362;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 indicates the year of last reapproval.Asuperscript epsilon()indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S.Department of Defense.1.Scope1.1 This specification covers the requirements for equip-ment intended to provide control input and monitoring oftemperatures in general applications.Equipment described inthis specification includes temperature indicators,signal con-ditioners and power supplies,and temperature sensors such asthermocouples and resistance temperature element assemblies.1.2 Special requirements for Naval shipboard applicationsare included in the Supplementary Requirements section.1.3 The values stated in SI units are to be regarded as thestandard.The values given in parentheses are for informationonly.2.Referenced Documents2.1 ASTM Standards:2D3951 Practice for Commercial PackagingE344 Terminology Relating to Thermometry and Hydrom-etry3.Terminology3.1 DefinitionsDefinitions of terminology shall be in ac-cordance with Terminology E344.4.Classification4.1 GeneralTemperature measuring devices are generallyclassified as either temperature sensors or thermometers.Ther-mometers are not covered by this specification.Temperaturesensors are classified by design and construction.Sensors mayalso be classified by the manner of response,basically me-chanical or electrical,to a change in temperature.Mechanicalresponse is characterized by some mechanical action as tem-perature changes.Electrical response is characterized by theproduction or change of an electrical signal or property astemperature changes.The following describes the most com-mon types of sensors:4.2 ThermocouplesThermocouples are constructed in avariety of designs to provide measurement of direct or differ-ential temperature.Thermocouples are commonly installedusing a thermowell which protects the thermocouple but alsodelays the rapid response time characteristic of thermocouples.4.2.1 Principle of OperationMost thermocouples utilizetwo wires fabricated from dissimilar metals joined at one endto form a measuring junction that is exposed to the processmedium being measured.The other ends of the wires areusually terminated at a measuring instrument which forms areference junction.When the two junctions are exposed todifferent temperatures,electrical current will flow through thecircuit(Seebeck Effect).The measurement of millivoltageresulting from the current is proportional to the temperaturebeing sensed.4.2.2 Types of ThermocouplesThermocouples can be di-vided into functional classes by materials and therefore,temperature ranges.The three classes are base metal,noblemetal,and refractory metal.Although many types are com-monly used in industrial applications,the Instrument Society ofAmerica(ISA)has assigned letter designations to seven types.By convention,the practice of using a slash mark to separatethe materials of each thermocouple wire is widely accepted.Likewise,the order in which the materials appear also denotespolarity of the wires;positive/negative when the measuringjunction is at a higher temperature than the reference junction.The following are examples of typical thermocouples:ClassTypeMaterialsTemperature(max)Base metalJIron/constantan1000C(1832F)Base metalTCopper/constantan1000C(1832F)Base metalKChromel/Alumel1000C(1832F)Base metalEChromel/constantan1000C(1832F)Base metal-Alloys of copper,nickel,iron,chromium,manganese,aluminum,andother metals1000C(1832F)Noble metal-Various noble metals2000C(3632F)Refractorymetal-Tungsten-rhenium,tantalum,molybdenum,and their alloys2600C(4712F)1This specification is under the jurisdiction of ASTM Committee F25 on Shipsand Marine Technology and is the direct responsibility of Subcommittee F25.10 onElectrical.Current edition approved Oct.1,2013.Published October 2013.Originallyapproved in 2003.Last previous edition approved in 2009 as F2362-03(2009).DOI:10.1520/F2362-03R13.2For 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 Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 4.3 ResistanceTemperatureMeasuringDevicesResistance thermometers measure changes in temperaturebased on changes in resistance of the sensor element exposedto the temperature.Two common types are resistance tempera-ture detectors which have metal sensor elements and thermis-tors which have semiconductor sensor elements.4.3.1 Resistance Temperature Detectors(RTDs)An RTDc