ASTM E377-08
(Practice)Standard Practice for Internal Temperature Measurements in Low-Conductivity Materials
Standard Practice for Internal Temperature Measurements in Low-Conductivity Materials
SIGNIFICANCE AND USE
Internal temperature measurements are made on both in-flight vehicles and on-ground test specimens; and, because of the importance of the temperature measurements to the design of various missile and spacecraft heat shields, it is essential that care be taken to minimize the sources of error in obtaining these measurements.
Over the past several years, the problems of using thermocouples to obtain accurate temperature measurements in low-conductivity specimens have been studied by various people to isolate the sources of error and to establish improved temperature measurement techniques. The major sources of error are listed in this document and recommended solutions to the problems are given.
SCOPE
1.1 This practice covers methods for instrumenting low-conductivity specimens for testing in an environment subject to rapid thermal changes such as produced by rocket motors, atmospheric re-entry, electric-arc plasma heaters, and so forth. Specifically, practices for bare-wire thermocouple instrumentation applicable to sheath-type thermocouples are discussed.
1.2 The values stated in inch-pound units are to be regarded as the standard. The metric equivalents of inch-pound units may be approximate.
1.3 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.
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Designation: E377 − 08
StandardPractice for
Internal Temperature Measurements in Low-Conductivity
1
Materials
This standard is issued under the fixed designation E377; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
2
1. Scope forming and using thermocouples , that is (1) electric welding
to form junctions, (2) maintaining cleanliness of junction area
1.1 This practice covers methods for instrumenting low-
and lead wires, (3) proper selection of thermocouple type and
conductivityspecimensfortestinginanenvironmentsubjectto
size, corresponding to both the temperature range to be
rapid thermal changes such as produced by rocket motors,
measured and the chemical compatibility with the
atmospheric re-entry, electric-arc plasma heaters, and so forth.
environment, and (4) proper use of instrumentation for readout
Specifically, practices for bare-wire thermocouple instrumen-
of thermocouple emf.
tation applicable to sheath-type thermocouples are discussed.
NOTE 1—Reader is referred toASTM MNL12 (1), and STP492 (2), as
1.2 The values stated in inch-pound units are to be regarded
well as Kinzie, P.A., Thermocouple Temperature Measurement (3), for
as the standard. The metric equivalents of inch-pound units
needed information.
may be approximate.
3.2 The most important sources of error beyond the above
1.3 This standard does not purport to address all of the
basic areas are the following:
safety concerns, if any, associated with its use. It is the
3.2.1 The thermal disturbance produced in the low-
responsibility of the user of this standard to establish appro-
conductivitymaterialatthevicinityofthethermocouplesensor
priate safety and health practices and determine the applica-
hot junction due to the sensor size, configuration, and instal-
bility of regulatory limitations prior to use.
lation method.
3.2.2 Electrical shorting of lead wires due to the electrical
2. Significance and Use
conductivity of the virgin or charred ablation material, and
2.1 Internal temperature measurements are made on both
3.2.3 Thermocouple sensor hot junction location accuracy.
in-flight vehicles and on-ground test specimens; and, because
4. Thermal Disturbance at Vicinity of Thermocouple
of the importance of the temperature measurements to the
Sensor Hot Junction
design of various missile and spacecraft heat shields, it is
essential that care be taken to minimize the sources of error in
4.1 General—Ideally, to measure the true internal tempera-
obtaining these measurements.
ture of a solid body, it would be desirable not to have any
foreign substance present that would create a disturbance
2.2 Over the past several years, the problems of using
affecting the natural flow of heat in the body. Since it is
thermocouplestoobtainaccuratetemperaturemeasurementsin
physically impossible to exclude the temperature sensor from
low-conductivity specimens have been studied by various
theinternalconfinesofthebody,itisnecessarythatthethermal
people to isolate the sources of error and to establish improved
disturbanceintroducedbythesensorbeminimizedforaccurate
temperature measurement techniques. The major sources of
temperature measurements (See Refs (4-10)).
error are listed in this document and recommended solutions to
the problems are given.
4.2 Thermocouple Junction Bead Diameter:
4.2.1 General—Excessively large junction beads result in
3. General
lower than true temperature measurements in low-conductivity
materials (conductivity of material less than conductivity of
3.1 Before proceeding to the major sources of error, it is
thermocouple wire) because of the heat sink effect of the bead.
assumed that the reader is familiar with basic methods of
4.2.2 Recommendations—To minimize this effect, the junc-
tion bead diameter should be no larger than 1.5 wire diameters
for butt-welded junctions and 2 wire diameters for other types
1
This practice is under the jurisdiction of ASTM Committee E21 on Space
Simulation andApplications of Space Technology and is the direct responsibility of of welds.
Subcommittee E21.08 on Thermal Protection.
Current edition approved Dec. 1, 2008. Published January 2009. Originally
2
approved in 1968. Last previous edition approved in 2002 as E377 – 96 (2002). ANSI MC96.1-1975. Temperature Measurement Thermocouples (Sponsor
DOI: 10.1520/E0377-08. ISA).
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
---------------------- Page: 1 ----------------------
E377 − 08
NOTE 1—If a number of thermocouples in depth are required, drill holes at varying locations on
...
This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:E377–96 (Reapproved 2002) Designation:E377–08
Standard Practice for
Internal Temperature Measurements in Low-Conductivity
1
Materials
This standard is issued under the fixed designation E 377; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice covers methods for instrumenting low-conductivity specimens for testing in an environment subject to rapid
thermal changes such as produced by rocket motors, atmospheric re-entry, electric-arc plasma heaters, and so forth. Specifically,
practices for bare-wire thermocouple instrumentation applicable to sheath-type thermocouples are discussed.
1.2 The values stated in inch-pound units are to be regarded as the standard. The metric equivalents of inch-pound units may
be approximate.
1.3 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.
2. Significance and Use
2.1 Internal temperature measurements are made on both in-flight vehicles and on-ground test specimens; and, because of the
importance of the temperature measurements to the design of various missile and spacecraft heat shields, it is essential that care
be taken to minimize the sources of error in obtaining these measurements.
2.2 Over the past several years, the problems of using thermocouples to obtain accurate temperature measurements in
low-conductivity specimens have been studied by various people to isolate the sources of error and to establish improved
temperature measurement techniques. The major sources of error are listed in this document and recommended solutions to the
problems are given.
3. General
3.1 Before proceeding to the major sources of error, it is assumed that the reader is familiar with basic methods of forming and
2
using thermocouples , that is (1) electric welding to form junctions, (2) maintaining cleanliness of junction area and lead wires,
(3) proper selection of thermocouple type and size, corresponding to both the temperature range to be measured and the chemical
compatibility with the environment, and (4) proper use of instrumentation for readout of thermocouple emf.
3
NOTE1—Reader is referred to ASTM MNL 12, and STP 492, as well as Kinzie, P.A., 1—Reader is referred to ASTM MNL 12 (1) , and STP 492(2),
as well as Kinzie, P.A., Thermocouple Temperature Measurement, for needed information. (3), for needed information.
3.2 The most important sources of error beyond the above basic areas are the following:
3.2.1 The thermal disturbance produced in the low-conductivity material at the vicinity of the thermocouple sensor hot junction
due to the sensor size, configuration, and installation method.
3.2.2 Electrical shorting of lead wires due to the electrical conductivity of the virgin or charred ablation material, and
3.2.3 Thermocouple sensor hot junction location accuracy.
4. Thermal Disturbance at Vicinity of Thermocouple Sensor Hot Junction
4.1 General—Ideally, to measure the true internal temperature of a solid body, it would be desirable not to have any foreign
substance present that would create a disturbance affecting the natural flow of heat in the body. Since it is physically impossible
to exclude the temperature sensor from the internal confines of the body, it is necessary that the thermal disturbance introduced
by the sensor be minimized for accurate temperature measurements. (See Refs (4-10)
4.2 Thermocouple Junction Bead Diameter:
1
This practice is under the jurisdiction of ASTM Committee E21 on Space Simulation and Applications of Space Technology and is the direct responsibility of
Subcommittee E21.08 on Thermal Protection.
Current edition approved Oct. 10, 1996. Published December 1996. Originally published as E377–68. Last previous edition E377–68(1992).
Current edition approved Dec. 1, 2008. Published January 2009. Originally approved in 1968. Last previous edition approved in 2002 as E 377 – 96 (2002).
2
ANSI MC96.1-1975. Temperature Measurement Thermocouples (Sponsor ISA).
3
The boldface numbers in parentheses refer to the list of references at the end of this practice.
Copyright © ASTM International, 100 Barr Harbor Drive, PO B
...
This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:E377–96 (Reapproved 2002) Designation:E377–08
Standard Practice for
Internal Temperature Measurements in Low-Conductivity
1
Materials
This standard is issued under the fixed designation E 377; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice covers methods for instrumenting low-conductivity specimens for testing in an environment subject to rapid
thermal changes such as produced by rocket motors, atmospheric re-entry, electric-arc plasma heaters, and so forth. Specifically,
practices for bare-wire thermocouple instrumentation applicable to sheath-type thermocouples are discussed.
1.2 The values stated in inch-pound units are to be regarded as the standard. The metric equivalents of inch-pound units may
be approximate.
1.3 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.
2. Significance and Use
2.1 Internal temperature measurements are made on both in-flight vehicles and on-ground test specimens; and, because of the
importance of the temperature measurements to the design of various missile and spacecraft heat shields, it is essential that care
be taken to minimize the sources of error in obtaining these measurements.
2.2 Over the past several years, the problems of using thermocouples to obtain accurate temperature measurements in
low-conductivity specimens have been studied by various people to isolate the sources of error and to establish improved
temperature measurement techniques. The major sources of error are listed in this document and recommended solutions to the
problems are given.
3. General
3.1 Before proceeding to the major sources of error, it is assumed that the reader is familiar with basic methods of forming and
2
using thermocouples , that is (1) electric welding to form junctions, (2) maintaining cleanliness of junction area and lead wires,
(3) proper selection of thermocouple type and size, corresponding to both the temperature range to be measured and the chemical
compatibility with the environment, and (4) proper use of instrumentation for readout of thermocouple emf.
NOTE 1—Reader is referred to ASTM MNL 12, and STP 492, as well as Kinzie, P.A., Thermocouple Temperature Measurement, for needed
information.
3.2 The most important sources of error beyond the above basic areas are the following:
3.2.1 The thermal disturbance produced in the low-conductivity material at the vicinity of the thermocouple sensor hot junction
due to the sensor size, configuration, and installation method.
3.2.2 Electrical shorting of lead wires due to the electrical conductivity of the virgin or charred ablation material, and
3.2.3 Thermocouple sensor hot junction location accuracy.
4. Thermal Disturbance at Vicinity of Thermocouple Sensor Hot Junction
4.1 General—Ideally, to measure the true internal temperature of a solid body, it would be desirable not to have any foreign
substance present that would create a disturbance affecting the natural flow of heat in the body. Since it is physically impossible
to exclude the temperature sensor from the internal confines of the body, it is necessary that the thermal disturbance introduced
by the sensor be minimized for accurate temperature measurements.
4.2 Thermocouple Junction Bead Diameter:
4.2.1 General—Excessively large junction beads result in lower than true temperature measurements in low-conductivity
1
This practice is under the jurisdiction of ASTM Committee E21 on Space Simulation and Applications of Space Technology and is the direct responsibility of
Subcommittee E21.08 on Thermal Protection.
Current edition approved Oct. 10, 1996. Published December 1996. Originally published as E377–68. Last previous edition E377–68(1992).
Current edition approved Dec. 1, 2008. Published January 2009. Originally approved in 1968. Last previous edition approved in 2002 as E 377 – 96 (2002).
2
ANSI MC96.1-1975. Temperature Measurement Thermocouples (Sponsor ISA).
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1
---------------------- Page: 1 -----------------
...
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