Standard Test Method for Calibration of Refractory Metal Thermocouples Using a Radiation Thermometer

SIGNIFICANCE AND USE
This test method is intended to be used by wire producers and thermocouple manufacturers for certification of refractory metal thermocouples. It is intended to provide a consistent method for calibration of refractory metal thermocouples referenced to a calibrated radiation thermometer. Uncertainty in calibration and operation of the radiation thermometer, and proper construction and use of the test furnace are of primary importance.
Calibration establishes the temperature-emf relationship for a particular thermocouple under a specific temperature and chemical environment. However, during high temperature calibration or application at elevated temperatures in vacuum, oxidizing, reducing or contaminating environments, and depending on temperature distribution, local irreversible changes may occur in the Seebeck Coefficient of one or both thermoelements. If the introduced inhomogeneities are significant, the emf from the thermocouple will depend on the distribution of temperature between the measuring and reference junctions.
At high temperatures, the accuracy of refractory metal thermocouples may be limited by electrical shunting errors through the ceramic insulators of the thermocouple assembly. This effect may be reduced by careful choice of the insulator material, but above approximately 2100 °C, the electrical shunting errors may be significant even for the best insulators available.
SCOPE
1.1 This test method covers the calibration of refractory metal thermocouples using a radiation thermometer as the standard instrument. This test method is intended for use with types of thermocouples that cannot be exposed to an oxidizing atmosphere. These procedures are appropriate for thermocouple calibrations at temperatures above 800 °C (1472 °F).
1.2 The calibration method is applicable to the following thermocouple assemblies:
1.2.1 Type 1 - Bare-wire thermocouple assemblies in which vacuum or an inert or reducing gas is the only electrical insulating medium between the thermoelements.
1.2.2 Type 2 - Assemblies in which loose fitting ceramic insulating pieces, such as single-bore or double-bore tubes, are placed over the thermoelements.
1.2.3 Type 2A - Assemblies in which loose fitting ceramic insulating pieces, such as single-bore or double-bore tubes, are placed over the thermoelements, permanently enclosed and sealed in a loose fitting metal or ceramic tube.
1.2.4 Type 3 - Swaged assemblies in which a refractory insulating powder is compressed around the thermoelements and encased in a thin-walled tube or sheath made of a high melting point metal or alloy.
1.2.5 Type 4 - Thermocouple assemblies in which one thermoelement is in the shape of a closed-end protection tube and the other thermoelement is a solid wire or rod that is coaxially supported inside the closed-end tube. The space between the two thermoelements can be filled with an inert or reducing gas, or with ceramic insulating materials, or kept under vacuum.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

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Historical
Publication Date
30-Apr-2007
Technical Committee
Current Stage
Ref Project

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ASTM E452-02(2007) - Standard Test Method for Calibration of Refractory Metal Thermocouples Using a Radiation Thermometer
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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: E452 − 02(Reapproved 2007)
Standard Test Method for
Calibration of Refractory Metal Thermocouples Using a
1
Radiation Thermometer
This standard is issued under the fixed designation E452; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
2
2.1 ASTM Standards:
1.1 This test method covers the calibration of refractory
E344Terminology Relating to Thermometry and Hydrom-
metal thermocouples using a radiation thermometer as the
etry
standard instrument. This test method is intended for use with
E563Practice for Preparation and Use of an Ice-Point Bath
types of thermocouples that cannot be exposed to an oxidizing
as a Reference Temperature
atmosphere. These procedures are appropriate for thermo-
E988Temperature-Electromotive Force (EMF) Tables for
couple calibrations at temperatures above 800°C (1472°F).
3
Tungsten-Rhenium Thermocouples (Withdrawn 2011)
1.2 The calibration method is applicable to the following
E1256Test Methods for Radiation Thermometers (Single
thermocouple assemblies:
Waveband Type)
1.2.1 Type 1—Bare-wire thermocouple assemblies in which
E1751Guide for Temperature Electromotive Force (EMF)
vacuum or an inert or reducing gas is the only electrical
Tables for Non-Letter Designated Thermocouple Combi-
insulating medium between the thermoelements. 3
nations (Withdrawn 2009)
1.2.2 Type 2—Assemblies in which loose fitting ceramic
3. Terminology
insulatingpieces,suchassingle-boreordouble-boretubes,are
placed over the thermoelements.
3.1 Definitions:
1.2.3 Type 2A—Assemblies in which loose fitting ceramic
3.1.1 For definitions of terms used in this test method see
insulatingpieces,suchassingle-boreordouble-boretubes,are
Terminology E344.
placed over the thermoelements, permanently enclosed and
3.1.2 radiation thermometer, n—radiometer calibrated to
sealed in a loose fitting metal or ceramic tube.
indicate the temperature of a blackbody.
1.2.4 Type 3—Swaged assemblies in which a refractory
3.1.2.1 Discussion—Radiationthermometersincludeinstru-
insulating powder is compressed around the thermoelements
ments having the following or similar names: (1) optical
and encased in a thin-walled tube or sheath made of a high
radiation thermometer, (2) photoelectric pyrometer, ( 3) single
melting point metal or alloy.
wavelength automatic thermometer, (4) disappearing filament
1.2.5 Type 4—Thermocouple assemblies in which one ther- pyrometer, (5) dual wavelength pyrometer or ratio radiation
moelement is in the shape of a closed-end protection tube and thermometer, (6) visual optical thermometer, (7) infrared
the other thermoelement is a solid wire or rod that is coaxially thermometer, (8) infrared pyrometer, and permutations on the
supported inside the closed-end tube. The space between the terms above as well as some manufacturer-specific names.
twothermoelementscanbefilledwithaninertorreducinggas,
3.2 Definitions of Terms Specific to This Standard:
or with ceramic insulating materials, or kept under vacuum.
3.2.1 automatic radiation thermometer, n— radiation ther-
1.3 This standard does not purport to address all of the
mometer whose temperature reading is determined by elec-
safety concerns, if any, associated with its use. It is the tronic means.
responsibility of the user of this standard to establish appro-
3.2.2 disappearing filament pyrometer, n— radiation ther-
priate safety and health practices and determine the applica-
mometer that requires an observer to match visually the
bility of regulatory limitations prior to use.
brightness of a heated filament mounted inside the radiation
thermometer to that of the measured object.
1 2
This test method is under the jurisdiction of ASTM Committee E20 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Temperature Measurementand is the direct responsibility of Subcommittee E20.04 contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
on Thermocouples. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved May 1, 2007. Published June 2007. Originally the ASTM website.
3
approved in 1972. Last previous edition approved in 2002 as E452–02. DOI: The last approved version of this historical standard is referenced on
10.1520/E0452-02R07. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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E452 − 02 (2007)
3.2.3 equalizing block, n—object, usually metal, that when 5. Significance and Use
placed in a nonunifor
...

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