ASTM E459-22

Standard Test Method for Measuring Heat Transfer Rate Using a Thin-Skin Calorimeter

SIGNIFICANCE AND USE
5.1 This test method may be used to measure the net heat transfer rate to a metallic or coated metallic surface for a variety of applications, including:  
5.1.1 Measurements of aerodynamic heating when the calorimeter is placed into a flow environment, such as a wind tunnel or an arc jet; the calorimeters can be designed to have the same size and shape as the actual test specimens to minimize heat transfer corrections;  
5.1.2 Heat transfer measurements in fires and fire safety testing;  
5.1.3 Laser power and laser absorption measurements; as well as,  
5.1.4 X-ray and particle beam (electrons or ions) dosimetry measurements.  
5.2 The thin-skin calorimeter is one of many concepts used to measure heat transfer rates. It may be used to measure convective, radiative, or combinations of convective and radiative (usually called mixed or total) heat transfer rates. However, when the calorimeter is used to measure radiative or mixed heat transfer rates, the absorptivity and reflectivity of the surface should be measured over the expected radiation wavelength region of the source, and as functions of temperature if possible.  
5.3 In 6.6 and 6.7, it is demonstrated that lateral heat conduction effects on a local measurement can be minimized by using a calorimeter material with a low thermal conductivity. Alternatively, a distribution of the heat transfer rate may be obtained by placing a number of thermocouples along the back surface of the calorimeter.  
5.4 In high temperature or high heat transfer rate applications, the principal drawback to the use of thin-skin calorimeters is the short exposure time necessary to ensure survival of the calorimeter such that repeat measurements can be made with the same sensor. When operation to burnout is necessary to obtain the desired heat flux measurements, thin-skin calorimeters are often a good choice because they are relatively inexpensive to fabricate.  
5.5 It is important to understand that the calorimeter design (th...
SCOPE
1.1 This test method covers the design and use of a thin metallic calorimeter for measuring heat transfer rate (also called heat flux). Thermocouples are attached to the unexposed surface of the calorimeter. A one-dimensional heat flow analysis is used for calculating the heat transfer rate from the temperature measurements. Applications include aerodynamic heating, laser and radiation power measurements, and fire safety testing.  
1.2 Advantages:  
1.2.1 Simplicity of Construction—The calorimeter may be constructed from a number of materials. The size and shape can often be made to match the actual application. Thermocouples may be attached to the metal by spot, electron beam, or laser welding.  
1.2.2 Heat transfer rate distributions may be obtained if metals with low thermal conductivity, such as some stainless steels or Inconel 600, are used.  
1.2.3 The calorimeters can be fabricated with smooth surfaces, without insulators or plugs and the attendant temperature discontinuities, to provide more realistic flow conditions for aerodynamic heating measurements.  
1.2.4 The calorimeters described in this test method are relatively inexpensive. If necessary, they may be operated to burn-out to obtain heat transfer information.  
1.3 Limitations:  
1.3.1 At higher heat flux levels, short test times are necessary to ensure calorimeter survival.  
1.3.2 For applications in wind tunnels or arc-jet facilities, the calorimeter must be operated at pressures and temperatures such that the thin-skin does not distort under pressure loads. Distortion of the surface will introduce measurement errors.  
1.3.3 Interpretation of the heat flux estimated may require additional analysis if the thin-skin calorimeter configuration is different from the test specimen.  
1.4 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.4.1 Exception—The values ...

General Information

• Status: Published
• Publication Date: 31-Mar-2022
• ICS: 17.200.10 - Heat. Calorimetry
• Technical Committee: E21 - Space Simulation and Applications of Space Technology
• Drafting Committee: E21.08 - Thermal Protection

Relations

• Refers: ASTM E176-24 - Standard Terminology of Fire Standards
• Effective Date: 01-Jan-2024
• Refers: ASTM E456-13a(2022)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Apr-2022
• Refers: ASTM E3057-19 - Standard Test Method for Measuring Heat Flux Using Directional Flame Thermometers with Advanced Data Analysis Techniques
• Effective Date: 01-Jun-2019
• Refers: ASTM E176-18a - Standard Terminology of Fire Standards
• Effective Date: 15-Dec-2018
• Refers: ASTM E176-18 - Standard Terminology of Fire Standards
• Effective Date: 01-Mar-2018
• Refers: ASTM E456-13A(2017)e1 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017
• Refers: ASTM E456-13A(2017)e3 - Standard Terminology Relating to Quality and Statistics
• Effective Date: 01-Oct-2017
• Refers: ASTM E3057-16 - Standard Test Method for Measuring Heat Flux Using Directional Flame Thermometers with Advanced Data Analysis Techniques
• Effective Date: 01-Apr-2016
• Refers: ASTM E176-15a - Standard Terminology of Fire Standards
• Effective Date: 01-Aug-2015
• Refers: ASTM E176-15ae1 - Standard Terminology of Fire Standards
• Effective Date: 01-Aug-2015
• Refers: ASTM E176-15 - Standard Terminology of Fire Standards
• Effective Date: 01-Feb-2015
• Refers: ASTM E176-14c - Standard Terminology of Fire Standards
• Effective Date: 01-Oct-2014
• Refers: ASTM E176-14b - Standard Terminology of Fire Standards
• Effective Date: 15-Aug-2014
• Refers: ASTM E176-14a - Standard Terminology of Fire Standards
• Effective Date: 01-Aug-2014
• Refers: ASTM E176-14 - Standard Terminology of Fire Standards
• Effective Date: 01-Jul-2014

Overview

ASTM E459-22, "Standard Test Method for Measuring Heat Transfer Rate Using a Thin-Skin Calorimeter," provides a standardized approach for determining net heat transfer rates on metallic or coated metallic surfaces. Developed by ASTM International, this test method utilizes a thin metallic calorimeter equipped with thermocouples to measure surface temperatures and apply a one-dimensional heat flow analysis. The method is crucial in industries where understanding thermal loads and heat flux is essential for safety, performance, and quality control.

Key Topics

• Thin-Skin Calorimeter Construction

  • Can be fabricated from a variety of metals
  • Size and shape can be customized to match actual test specimens
  • Thermocouples are attached to the unexposed surface via spot, electron beam, or laser welding

• Measurement Principles

  • Relies on one-dimensional heat flow through the calorimeter
  • Measures net heat flux (combining absorbed, emitted, and convective heat transfer)
  • Requires thermophysical property knowledge (specific heat, thermal conductivity, density)

• Advantages

  • Simple, cost-effective construction
  • Realistic flow condition simulation due to smooth surfaces, free from insulators or plugs
  • Possibility to obtain heat transfer distributions with low thermal conductivity metals
  • Reusable for repeat measurements or operated to burn-out if required

• Limitations and Uncertainties

  • Short exposure times required at high heat flux
  • Surface distortion at high temperature and pressure can affect results
  • Additional analysis needed if calorimeter configuration differs from the test specimen
  • Measurement uncertainties relate to thermocouple performance, data acquisition, and material properties

Applications

ASTM E459-22 is widely used across various sectors for heat transfer measurement, including:

• Aerodynamic Heating

  • Testing thermal protection systems and components in wind tunnels and arc jet environments
  • Simulating real-world aerospace conditions by matching calorimeter geometry with test specimens

• Fire Safety Testing

  • Evaluating material and system response under fire exposure scenarios
  • Measuring combined convective and radiative heat transfer in fire environments

• Laser and Radiation Power Measurement

  • Quantifying energy absorption and distribution for laser applications
  • Assessing X-ray and particle beam dosimetry by determining energy deposition rates

• Research and Development

  • Material property characterization for new or experimental alloys
  • Verification of numerical models for thermal analysis

Related Standards

For comprehensive thermal measurement and data analysis, ASTM E459-22 is commonly referenced alongside:

• ASTM E457 - Standard Test Method for Measuring Heat-Transfer Rate Using a Thermal Capacitance (Slug) Calorimeter
• ASTM E3057 - Test Method for Measuring Heat Flux Using Directional Flame Thermometers with Advanced Data Analysis Techniques
• ASTM E176 - Terminology of Fire Standards
• ASTM E230 - Specification for Temperature-Electromotive Force (emf) Tables for Standardized Thermocouples
• ASTM E235 - Specification for Type K and Type N Mineral-Insulated, Metal-Sheathed Thermocouples for High-Reliability Applications

Practical Value

Applying ASTM E459-22 ensures accurate, repeatable measurement of heat flux under controlled laboratory or real-world conditions. Its guidance improves safety testing, optimizes material selection, supports product development, and strengthens compliance with regulatory requirements in industries such as aerospace, defense, fire protection, and energy. By following this standard, users benefit from best practices in heat transfer measurement, leading to more reliable and comparable results across different testing environments.

Keywords: heat transfer rate, heat flux measurement, thin-skin calorimeter, ASTM E459-22, fire safety testing, aerodynamic heating, thermocouples, laser power measurement, net heat flux, standard test method.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E459 − 22
Standard Test Method for
Measuring Heat Transfer Rate Using a Thin-Skin
Calorimeter
This standard is issued under the fixed designation E459; 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 1.4 Units—The values stated in SI units are to be regarded
as standard. No other units of measurement are included in this
1.1 This test method covers the design and use of a thin
standard.
metallic calorimeter for measuring heat transfer rate (also
1.4.1 Exception—The values given in parentheses are for
called heat flux). Thermocouples are attached to the unexposed
information only.
surface of the calorimeter. A one-dimensional heat flow analy-
1.5 This standard does not purport to address all of the
sis is used for calculating the heat transfer rate from the
safety concerns, if any, associated with its use. It is the
temperature measurements. Applications include aerodynamic
responsibility of the user of this standard to establish appro-
heating, laser and radiation power measurements, and fire
priate safety, health, and environmental practices and deter-
safety testing.
mine the applicability of regulatory limitations prior to use.
1.2 Advantages:
1.6 This international standard was developed in accor-
1.2.1 Simplicity of Construction—The calorimeter may be
dance with internationally recognized principles on standard-
constructed from a number of materials. The size and shape can
ization established in the Decision on Principles for the
often be made to match the actual application. Thermocouples
Development of International Standards, Guides and Recom-
may be attached to the metal by spot, electron beam, or laser
mendations issued by the World Trade Organization Technical
welding.
Barriers to Trade (TBT) Committee.
1.2.2 Heat transfer rate distributions may be obtained if
metals with low thermal conductivity, such as some stainless
2. Referenced Documents
steels or Inconel 600, are used.
2.1 ASTM Standards:
1.2.3 The calorimeters can be fabricated with smooth
E176 Terminology of Fire Standards
surfaces, without insulators or plugs and the attendant tempera-
E230 Specification for Temperature-Electromotive Force
ture discontinuities, to provide more realistic flow conditions
(emf) Tables for Standardized Thermocouples
for aerodynamic heating measurements.
E235 Specification for Type K and Type N Mineral-
1.2.4 The calorimeters described in this test method are
Insulated, Metal-Sheathed Thermocouples for Nuclear or
relatively inexpensive. If necessary, they may be operated to
for Other High-Reliability Applications
burn-out to obtain heat transfer information.
E456 Terminology Relating to Quality and Statistics
1.3 Limitations:
E3057 Test Method for Measuring Heat Flux Using Direc-
1.3.1 At higher heat flux levels, short test times are neces-
tional Flame Thermometers with Advanced Data Analysis
sary to ensure calorimeter survival.
Techniques
1.3.2 For applications in wind tunnels or arc-jet facilities,
E457 Test Method for Measuring Heat-Transfer Rate Using
the calorimeter must be operated at pressures and temperatures
a Thermal Capacitance (Slug) Calorimeter
such that the thin-skin does not distort under pressure loads.
Distortion of the surface will introduce measurement errors.
3. Terminology
1.3.3 Interpretation of the heat flux estimated may require
3.1 Definitions—Refer to Terminologies E176 and E456 for
additional analysis if the thin-skin calorimeter configuration is
definitions of terms used in this test method.
different from the test specimen.
3.2 Definitions of Terms Specific to This Standard:
This test method 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. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved April 1, 2022. Published May 2022. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1972. Last previous edition approved in 2016 as E459 – 05(2016). DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/E0459-22. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E459 − 22
3.2.1 absorbed heat flux, n—incident radiative heat flux less 3.4.8 U —total uncertainty to 95 % confidence
the reflected radiative flux, W/m .
4. Summary of Test Method
3.2.2 convective heat flux, n—the addition or loss of energy
4.1 This test method for measuring the heat transfer rate to
per unit area into the sensing surface due to convection, =
h*(T -T ), W/m . a metal calorimeter of finite thickness is based on the assump-
fs s
tion of one-dimensional heat flow, known metal properties
3.2.3 control volume, n—user defined volume over which an
(density and specific heat as functions of temperature), known
energy balance is determined.
metal thickness, and measurement of the rate of temperature
3.2.4 emitted heat flux, n—energy per unit area emitted from
rise of the back (or unexposed) surface of the calorimeter.
4 2
a hot surface – ε*σ*T , W/m .
4.2 After an initial transient, the response of the calorimeter
3.2.5 incident radiative heat flux (irradiance; q ),
inc,r
is approximated by a lumped parameter analysis:
n—radiative heat flux (energy per unit area) impinging on the
dT
surface of the calorimeter from an external environment,
q 5 ρC δ (1)
S D
2 lumped p
dt
W/m .
3.2.6 heat flux, n—energy per unit area, W/m .
where:
3.2.7 lumped heat flux, n—the energy stored in the metal q = heat transfer rate, W/m , stored in the metal
lumped
plate divided by the surface area of the sensing surface, W/m . calorimeter,
ρ = metal density, kg/m ,
3.2.8 net heat flux, n—net energy divided by the sensing
δ = metal thickness, m,
surface area transferred to the calorimeter face; it is equal to the
C = metal specific heat, J/kg·K, and
p
[absorbed radiative heat flux + convective heat flux] – [re-
dT/dt = back surface temperature rise rate, K/s.
radiation from the exposed surface].
Use of Eq 1 assumes that the user understands the limitations
3.2.9 reflected heat flux, n—that part of the incident radia-
of how the heat flux is interpreted. See Appendix X1 for more
tive flux that is not absorbed by or transmitted into the surface
discussion related to this topic.
of the calorimeter, W/m .
3.2.10 verified, n—the process of checking that a data
5. Significance and Use
acquisition channel correctly measures an input value, to a
5.1 This test method may be used to measure the net heat
pre-set, acceptable level condition defined by the user.
transfer rate to a metallic or coated metallic surface for a
3.3 Symbols Specific to This Standard:
variety of applications, including:
A—sensing surface area of calorimeter, m
5.1.1 Measurements of aerodynamic heating when the calo-
Cp—specific heat at constant pressure of metal as a function
rimeter is placed into a flow environment, such as a wind
of temperature, J/(kg-K)
tunnel or an arc jet; the calorimeters can be designed to have
h—convective heat transfer coefficient, W/m -K
the same size and shape as the actual test specimens to
k—thermal conductivity of metal as a function of
minimize heat transfer corrections;
temperature, W/(m-K)
5.1.2 Heat transfer measurements in fires and fire safety
ρ—density of metal, kg/m
testing;
q—heat flux, W/m
5.1.3 Laser power and laser absorption measurements; as
q˙ —MW/m (Figs. 2 and 3 only)
well as,
q —energy per unit area stored in the metal calorimeter, 5.1.4 X-ray and particle beam (electrons or ions) dosimetry
lumped
W/m measurements.
t —time, sec
5.2 The thin-skin calorimeter is one of many concepts used
T—temperature, K
to measure heat transfer rates. It may be used to measure
T —free stream fluid temperature, K
fs
convective, radiative, or combinations of convective and ra-
T —surface temperature of thin-skin calorimeter, K
s
diative (usually called mixed or total) heat transfer rates.
δ—metal thickness, m
However, when the calorimeter is used to measure radiative or
ε—emissivity of sensing surface
mixed heat transfer rates, the absorptivity and reflectivity of the
2 4
σ—Stefan-Boltzmann constant, 5.67E-08 W/m -K
surface should be measured over the expected radiation wave-
τ —initial response time, sec
r
length region of the source, and as functions of temperature if
possible.
3.4 Abbreviations:
3.4.1 B —total bias uncertainty
T
5.3 In 6.6 and 6.7, it is demonstrated that lateral heat
3.4.2 DOF—degrees of freedom conduction effects on a local measurement can be minimized
by using a calorimeter material with a low thermal conductiv-
3.4.3 ms—milliseconds
ity. Alternatively, a distribution of the heat transfer rate may be
3.4.4 OD—outer diameter
obtained by placing a number of thermocouples along the back
3.4.5 S —total systematic or precision uncertainty
T surface of the calorimeter.
3.4.6 TC—thermocouple
5.4 In high temperature or high heat transfer rate
3.4.7 t —“Students t” applications, the principal drawback to the use of thin-skin
E459 − 22
FIG. 1 Typical Thin-Skin Calorimeter for Heat Transfer Measurement
calorimeters is the short exposure time necessary to ensure surface (1, 2). The wires should be positioned approximately
survival of the calorimeter such that repeat measurements can 1.6 mm apart along an expected isotherm. The use of a small
be made with the same sensor. When operation to burnout is thermocouple (for example, 0.127 mm (0.005 in.) OD, 36
necessary to obtain the desired heat flux measurements, thin-
gage) wire minimizes heat conduction into the wire but the
skin calorimeters are often a good choice because they are
calorimeter should still be rugged enough for repeated mea-
relatively inexpensive to fabricate.
surements. However, when the thickness of the calorimeter is
less than the wire diameter (to obtain the necessary response
5.5 It is important to understand that the calorimeter design
characteristics), it is possible that the presence of the TC will
(that is, that shown in Fig. 1) will measure the “net” heat flux
locally depress the temperature of the thin-skin. As a general
into the thin-skin calorimeter. This configuration may or may
rule of thumb, one should size the TC wire diameter no larger
not be the same as the test specimen of interest. If it is the same
configuration, then the results from use of Eq 1 can be used than the thickness of the calorimeter (δ). Further information
on this topic is provided in the recommendations of Sobolik, et
directly. But if the configuration is different, then some
additional analysis should be performed. For example, if the al. [1989], Burnett [1961], and Kidd [1985] (2-4).
actual test specimen has an insulated layer on the inside surface
6.2 When heating starts, the response of the back (unheated)
of the thin-skin, but the thin-skin calorimeter does not, then the
surface of the calorimeter lags behind that of the front (heated)
net heat flux from Eq 1 will not be the same as the response of
surface. For a step change in the heat transfer rate, the initial
the test specimen. Refer to Appendix X1 for further discussion
response time of the calorimeter is the time required for the
of this topic.
temperature rise rate of the unheated surface to approach the
temperature rise rate of the front surface within 1 %. If
6. Apparatus
conduction heat transfer into the thermocouple wire is ignored,
6.1 Calorimeter Design—Typical details of a thin-skin calo-
the initial response time is generally defined as:
rimeter used for measuring aerodynamic heat transfer rates are
ρC δ
shown in Fig. 1. (See also E457.) The thermocouple wires are p
τ 5 0.5 * (2)
S D
r
k
individually welded to the back surface of the calorimeter
using spot, electron beam, or laser techniques. This type of
thermocouple joint (called an intrinsic thermocouple) has been
found to provide superior transient response as compared to a
The boldface numbers in parentheses refer to the list of references at the end of
peened joint or a beaded thermocouple that is soldered to the this standard.
E459 − 22
where: errors (1, 5) should be used to compensate the temperature
measurements before calculating the heat flux using Eq 1.
τ = initial response time, s, and
r
k = thermal conductivity, W/m·K.
6.4 Determine the maximum exposure time (6) by setting a
As an example, the 0.76 mm (0.030 in.) thick, 300 series maximum allowable temperature for the front surface as
follows:
stainless steel calorimeter analyzed in Ref (4) has an initial
response time of 72 ms. Eq 2 can be rearranged to show that 2
ρC δ k T 2 T 1
~ !
p max 0
τ 5 * 2 (4)
S D FS D S D G
the initial response time also corresponds to a Fourier Number max
k qδ 3
(a dimensionless time) of 0.5.
where:
6.3 Conduction heat transfer into the thermocouple wire
τ = maximum exposure time, s,
max
delays the time predicted by Eq 2 for which the measured back
T = initial temperature, K, and
face temperature rise rate accurately follows (that is, within
T = maximum allowable temperature, K.
max
1 %) the undisturbed back face temperature rise rate. For a
6.4.1 In order to have time available for the heat transfer
0.127 mm (0.005 in.) OD, Type K intrinsic thermocouple on a
0.76 mm (0.030 in.) thick, 300 series stainless steel rate measurement, τ must be greater than τ , which requires
max r
calorimeter, the analysis in Ref (4) indicates the measured that:
temperature rise rate is within 2 % of the undisturbed tempera-
k T 2 T 5
~ !
max 0
. (5)
ture rise rate in approximately 500 ms. An estimate of the
qδ 6
measured temperature rise rate error (or slope error) can be
6.4.2 Determine an optimum thickness that maximizes
obtained from Ref (1) for different material combinations:
(τ − τ ) (7) as follows:
max r
dT dT C αt αt
C TC 2
2 5 C exp *erfcS C D (3)
Π3 k T 2 T
S 2 D 2 ~ !
1 2 max 0
dt dt R R
δ 5 * (6)
S D
opt
5 q
where:
6.4.3 Then calculate the maximum exposure time using the
T = calorimeter temperature,
C
optimum thickness as follows:
T = measured temperature (that is, thermocouple output),
TC
C = β/(8/π + β) and C = 4 ⁄(8 ⁄π + βπ),
T 2 T
1 2 max 0
τ 5 0.48ρC k * (7)
F G
maxopt p
α = k/ρC (thermal diffusivity of the calorimeter material),
q
p
β =
K/=A ,
6.4.4 When it is desirable for a calorimeter to cover a range
K = k of thermocouple wire/k of calorimeter,
of heat transfer rates without being operated to burn-out,
A = α of thermocouple wire/α of calorimeter,
design the calorimeter around the largest heat transfer rate.
R = radius of the thermocouple wire, and
This gives the thinnest calorimeter with the shortest initial
t = time.
response time (Eq 2); however, Refs (2, 3, 8, 9) all show the
Using thermal property values given in Ref (4) for the
time to a given error level between the measured and undis-
Alumel (negative) leg of the Type K thermocouple on 300
turbed temperature rise rates (left hand side of Eq 3) increases
Series stainless steel (K = 1.73, A = 1.56, β = 1.39), Eq 3 can
as the thickness of the calorimeter decreases relative to the
be used to show that the measured rate of temperature change
thermocouple wire diameter.
(that is, the slope) is within 5 % of the actual rate of
temperature change in approximately 150 ms. For this case, the
6.5 In most applications, the value of T should be well
max
time for a 1 % error in the measured temperature rise rate is
below the melting temperature to obtain a satisfactory design.
roughly 50 times as long as the initial response time predicted
Limiting the maximum temperature to 700 K will keep
by Eq 2; this ratio depends on the thermophysical properties of
radiation losses below 15 kW/m . For a maximum temperature
the calorimeter and thermocouple materials (see Table 1).
rise (T − T ) of 400 K, Fig. 2 shows the optimum thickness
max 0
6.3.1 When the heat transfer rate varies with time, the
of copper and stainless steel calorimeters as a function of the
thin-skin calorimeter should be designed so the response times
heat transfer rate. The maximum exposure time of an optimum
defined using Eq 2 and 3 are smaller than the time for
thickness calorimeter for a 400 K temperature rise is shown as
significant variations in the heat transfer rate. If this is not
a function of the heat transfer rate in Fig. 3.
possible, methods for unfolding the dynamic measurement
6.6 The one-dimensional heat flow assumption used in 4.2
and 6.3–6.4 is valid for a uniform heat transfer rate; however,
in practice, the calorimeter will generally have a heat transfer
rate distribution over the surface. Refs (9, 10) both consider the
TABLE 1 Time Required for Different Error Levels in the
Unexposed Surface Temperature Rise Rate effects of lateral heat conduction in a hemispherical calorimeter
on heat transfer measurements in a supersonic stream. For a
Error Level Due to Heat
Conduction into 10 % 5 % 2 % 1 %
cosine shaped heat flux distribution at the stagnation-point of
Thermocouple
the hemisphere, Starner (10) gives the lateral conduction error
Negative Leg (Alumel) of 35 ms 150 ms 945 ms 3.8 s
relative to the surface heating as
Type K on 304 Stainless
Negative Leg (Constantan) <1 ms <1 ms 1 ms 4 ms
2αt 8kt
of Type T on Copper
E 5 5 (8)
CL 2 2
R ρC D
p
E459 − 22
FIG. 2 Calorimeter Optimum Material Thickness as a Function of Heat Transfer Rate and Material
where: change. The analysis was developed for laser experiments
where only part of the calorimeter surface was exposed to
E = relative heat transfer rate ratio,
heating and the exposure time was long compared to the
R = radius of curvature of the body (D/2),
t = exposure time, and thermal penetration time to the edges of the unexposed area
C = centerline. (penetration time calculation is similar to Eq 2 with L, the
L
distance to the edge, substituted for δ, the thickness).
Note the lateral conduction error described in Eq 8 is not a
function of the calorimeter skin thickness or the heat transfer
6.9 A device for recording the thermocouple signals with
rate; the magnitude of the error is shown in Fig. 4 for copper
time is required. The response time (τ ) of an analog recording
r
and stainless steel. The errors for most other base metal
system should be an order of magnitude smaller than the
calorimeters will fall in between these two lines. While the
calorimeter response time (see Eq 2). The sampling time of a
lateral conduction errors can be minimized by using materials
digital recording system should be no more than 40 % of the
with low thermal diffusivity and short exposure times, these
calorimeter response time; the 3 db frequency of any low-pass
may aggravate some of the other constraints, as described in Eq
filters in the data acquisition system should be greater than
2 and 3. Ref (9) also describes the lateral conduction errors for
1 h
cones and cylinders. f . 5 (10)
S D S D
3db
2πτ 2πρC δ
r p
6.7 A rough estimate of the lateral conduction error during
where:
the test can be obtained experimentally by continuing to record
h = estimated heat transfer coefficient for the experiment.
the unexposed surface temperature after the heating is removed
and calculating the ratio of the rates of temperature change.
7. Hazards
dT dt
cooldown
/
E; (9) 7.1 This standard does not purport to address all of the
dT dt
/ test
safety concerns, if any, associated with its use. It is the
6.8 When the average heat transfer rate over the exposed responsibility of the user of this standard to establish appro-
area is desired, Wedekind and Beck [1989] (11) give another priate safety, health, and environmental practices and deter-
approach for evaluation of the measured rate of temperature mine the applicability of regulatory limitations prior to use.
E459 − 22
FIG. 3 Maximum Exposure Time for an Optimum Thickness Calorimeter as a Function of Heat Transfer Rate and Material
FIG. 4 Radial Conduction as a Function of Time and Material
8. Calibration and Standardization ments. For example, it is not possible to obtain bias errors for
thermocouples mounted on surfaces because the bias errors
8.1 It is desirable, but most often not possible, to obtain
depend on specifics of the setup, which varies for each different
estimates of the precision and bias of all sensors and instru-
E459 − 22
test. As a result, most often manufacturers provide information 9.3 Take enough measurements with the same calorimeter at
for the sensor only. For example, ASTM’s specifications for a particular test condition to obtain an estimate of the repro-
thermocouple accuracy are provided in Specification E230 as ducibility of the technique. The density and thickness of the
“tolerances.” An example for Type K thermocouples is a calorimeter material should be determined with good accuracy.
standard tolerance of “the greater of 62.2 °C or 60.75 % of If the calorimeter is used over temperature ranges where the
the reading in °C”. There is no mention of a precision or bias specific heat of the calorimeter material is well established; the
in that tolerance; it would be very difficult to obtain such measurement of the heat transfer rate on the exposed surface
numbers. Also, most manufacturers do not provide an estimate may be made with the same accuracy as the measurement of
of the confidence level associated with the accuracy specifica- the rate of temperature rise of the unexposed surface.
tion. For example, one does not often see a specification like
9.4 Uncertainties in relating these measurements to the
this: the accuracy is 65 % with a confidence level of 95 %. The
thermal environment can occur for a number of reasons. In
manufacturer only provides this: the accuracy is 65 %.
high temperature gas flows such as flames or arc-heated jets,
Fortunately, many specifications imply the accuracy specifica-
ionization and catalytic effects can introduce uncertainties. For
tion assumes the highest confidence, that is, about 99 %. A
radiation heat transfer, uncertainties in the surface properties
detailed assessment of thermo
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM 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: E459 − 05 (Reapproved 2016) E459 − 22
Standard Test Method for
Measuring Heat Transfer Rate Using a Thin-Skin
Calorimeter
This standard is issued under the fixed designation E459; 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 test method covers the design and use of a thin metallic calorimeter for measuring heat transfer rate (also called heat flux).
Thermocouples are attached to the unexposed surface of the calorimeter. A one-dimensional heat flow analysis is used for
calculating the heat transfer rate from the temperature measurements. Applications include aerodynamic heating, laser and
radiation power measurements, and fire safety testing.
1.2 Advantages:
1.2.1 Simplicity of Construction—The calorimeter may be constructed from a number of materials. The size and shape can often
be made to match the actual application. Thermocouples may be attached to the metal by spot, electron beam, or laser welding.
1.2.2 Heat transfer rate distributions may be obtained if metals with low thermal conductivity, such as some stainless steels, steels
or Inconel 600, are used.
1.2.3 The calorimeters can be fabricated with smooth surfaces, without insulators or plugs and the attendant temperature
discontinuities, to provide more realistic flow conditions for aerodynamic heating measurements.
1.2.4 The calorimeters described in this test method are relatively inexpensive. If necessary, they may be operated to burn-out to
obtain heat transfer information.
1.3 Limitations:
1.3.1 At higher heat flux levels, short test times are necessary to ensure calorimeter survival.
1.3.2 For applications in wind tunnels or arc-jet facilities, the calorimeter must be operated at pressures and temperatures such that
the thin-skin does not distort under pressure loads. Distortion of the surface will introduce measurement errors.
1.3.3 Interpretation of the heat flux estimated may require additional analysis if the thin-skin calorimeter configuration is different
from the test specimen.
1.4 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this
standard.
This test method 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 April 1, 2016April 1, 2022. Published April 2016May 2022. Originally approved in 1972. Last previous edition approved in 20112016 as
E459 – 05 (2011).(2016). DOI: 10.1520/E0459-05R16.10.1520/E0459-22.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E459 − 22
1.4.1 Exception—The values given in parentheses are for information only.
1.5 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
E176 Terminology of Fire Standards
E230 Specification for Temperature-Electromotive Force (emf) Tables for Standardized Thermocouples
E235 Specification for Type K and Type N Mineral-Insulated, Metal-Sheathed Thermocouples for Nuclear or for Other
High-Reliability Applications
E456 Terminology Relating to Quality and Statistics
E3057 Test Method for Measuring Heat Flux Using Directional Flame Thermometers with Advanced Data Analysis Techniques
E457 Test Method for Measuring Heat-Transfer Rate Using a Thermal Capacitance (Slug) Calorimeter
3. Terminology
3.1 Definitions—Refer to Terminologies E176 and E456 for definitions of terms used in this test method.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 absorbed heat flux, n—incident radiative heat flux less the reflected radiative flux, W/m .
3.2.2 convective heat flux, n—the addition or loss of energy per unit area into the sensing surface due to convection, = h*(T -T ),
fs s
W/m .
3.2.3 control volume, n—user defined volume over which an energy balance is determined.
4 2
3.2.4 emitted heat flux, n—energy per unit area emitted from a hot surface – ε*σ*T , W/m .
3.2.5 incident radiative heat flux (irradiance; q ), n—radiative heat flux (energy per unit area) impinging on the surface of the
inc,r
calorimeter from an external environment, W/m .
3.2.6 heat flux, n—energy per unit area, W/m .
3.2.7 lumped heat flux, n—the energy stored in the metal plate divided by the surface area of the sensing surface, W/m .
3.2.8 net heat flux, n—net energy divided by the sensing surface area transferred to the calorimeter face; it is equal to the [absorbed
radiative heat flux + convective heat flux] – [re-radiation from the exposed surface].
3.2.9 reflected heat flux, n—that part of the incident radiative flux that is not absorbed by or transmitted into the surface of the
calorimeter, W/m .
3.2.10 verified, n—the process of checking that a data acquisition channel correctly measures an input value, to a pre-set,
acceptable level condition defined by the user.
3.3 Symbols Specific to This Standard:
A—sensing surface area of calorimeter, m
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
E459 − 22
Cp—specific heat at constant pressure of metal as a function of temperature, J/(kg-K)
h—convective heat transfer coefficient, W/m -K
k—thermal conductivity of metal as a function of temperature, W/(m-K)
ρ—density of metal, kg/m
q—heat flux, W/m
q˙ —MW/m (Figs. 2 and 3 only)
q —energy per unit area stored in the metal calorimeter, W/m
lumped
t —time, sec
T—temperature, K
T —free stream fluid temperature, K
fs
T —surface temperature of thin-skin calorimeter, K
s
δ—metal thickness, m
ε—emissivity of sensing surface
2 4
σ—Stefan-Boltzmann constant, 5.67E-08 W/m -K
τ —initial response time, sec
r
3.4 Abbreviations:
3.4.1 B —total bias uncertainty
T
3.4.2 DOF—degrees of freedom
3.4.3 ms—milliseconds
3.4.4 OD—outer diameter
3.4.5 S —total systematic or precision uncertainty
T
3.4.6 TC—thermocouple
3.4.7 t —“Students t”
3.4.8 U —total uncertainty to 95 % confidence
4. Summary of Test Method
4.1 This test method for measuring the heat transfer rate to a metal calorimeter of finite thickness is based on the assumption of
one-dimensional heat flow, known metal properties (density and specific heat), heat as functions of temperature), known metal
thickness, and measurement of the rate of temperature rise of the back (or unexposed) surface of the calorimeter.
4.2 After an initial transient, the response of the calorimeter is approximated by a lumped parameter analysis:
dT
q 5 ρC δ (1)
p
dτ
dT
q 5 ρC δ (1)
S D
lumped p
dt
where:
q = heat transfer rate, W/m , stored in the metal calorimeter,
lumped
ρ = metal density, kg/m ,
δ = metal thickness, m,
C = metal specific heat, J/kg·K, and
p
dT/dτ = back surface temperature rise rate, K/s.
dT/dt = back surface temperature rise rate, K/s.
Use of Eq 1 assumes that the user understands the limitations of how the heat flux is interpreted. See Appendix X1 for more
discussion related to this topic.
E459 − 22
5. Significance and Use
5.1 This test method may be used to measure the net heat transfer rate to a metallic or coated metallic surface for a variety of
applications, including:
5.1.1 Measurements of aerodynamic heating when the calorimeter is placed into a flow environment, such as a wind tunnel or an
arc jet; the calorimeters can be designed to have the same size and shape as the actual test specimens to minimize heat transfer
corrections;
5.1.2 Heat transfer measurements in fires and fire safety testing;
5.1.3 Laser power and laser absorption measurements; as well as,
5.1.4 X-ray and particle beam (electrons or ions) dosimetry measurements.
5.2 The thin-skin calorimeter is one of many concepts used to measure heat transfer rates. It may be used to measure convective,
radiative, or combinations of convective and radiative (usually called mixed or total) heat transfer rates. However, when the
calorimeter is used to measure radiative or mixed heat transfer rates, the absorptivity and reflectivity of the surface should be
measured over the expected radiation wavelength region of the source.source, and as functions of temperature if possible.
5.3 In 4.66.6 and 4.76.7, it is demonstrated that lateral heat conduction effects on a local measurement can be minimized by using
a calorimeter material with a low thermal conductivity. Alternatively, a distribution of the heat transfer rate may be obtained by
placing a number of thermocouples along the back surface of the calorimeter.
5.4 In high temperature or high heat transfer rate applications, the principal drawback to the use of thin-skin calorimeters is the
short exposure time necessary to ensure survival of the calorimeter such that repeat measurements can be made with the same
sensor. When operation to burnout is necessary to obtain the desired heat flux measurements, thin-skin calorimeters are often a
good choice because they are relatively inexpensive to fabricate.
FIG. 1 Typical Thin-Skin Calorimeter for Heat Transfer Measurement
E459 − 22
5.5 It is important to understand that the calorimeter design (that is, that shown in Fig. 1) will measure the “net” heat flux into
the thin-skin calorimeter. This configuration may or may not be the same as the test specimen of interest. If it is the same
configuration, then the results from use of Eq 1 can be used directly. But if the configuration is different, then some additional
analysis should be performed. For example, if the actual test specimen has an insulated layer on the inside surface of the thin-skin,
but the thin-skin calorimeter does not, then the net heat flux from Eq 1 will not be the same as the response of the test specimen.
Refer to Appendix X1 for further discussion of this topic.
6. Apparatus
6.1 Calorimeter Design—Typical details of a thin-skin calorimeter used for measuring aerodynamic heat transfer rates are shown
in Fig. 1. (See also E457.) The thermocouple wires (0.127 mm OD, 0.005 in., 36 gage) are individually welded to the back surface
of the calorimeter using spot, electron beam, or laser techniques. This type of thermocouple joint (called an intrinsic thermocouple)
has been found to provide superior transient response as compared to a peened joint or a beaded thermocouple that is soldered to
the surface (1, 2). The wires should be positioned approximately 1.6 mm 1.6 mm apart along an expected isotherm. The use of
a small thermocouple (for example, 0.127 mm (0.005 in.) OD, 36 gage) wire minimizes heat conduction into the wire but the
calorimeter should still be rugged enough for repeated measurements. However, when the thickness of the calorimeter is on the
order of the less than the wire diameter to(to obtain the necessary response characteristics, the characteristics), it is possible that
the presence of the TC will locally depress the temperature of the thin-skin. As a general rule of thumb, one should size the TC
wire diameter no larger than the thickness of the calorimeter (δ). Further information on this topic is provided in the
recommendations of Sobolik, et al. [1989], Burnett [1961], and Kidd [1985] (2-4)). should be followed.
6.2 When heating starts, the response of the back (unheated) surface of the calorimeter lags behind that of the front (heated)
surface. For a step change in the heat transfer rate, the initial response time of the calorimeter is the time required for the
temperature rise rate of the unheated surface to approach the temperature rise rate of the front surface within 1 %. If conduction
heat transfer into the thermocouple wire is ignored, the initial response time is generally defined as:
ρC δ
p
τ 5 0.5 (2)
r
k
ρC δ
p
τ 5 0.5 * (2)
S D
r
k
where:
τ = initial response time, s, and
r
k = thermal conductivity, W/m·K.
As an example, the 0.76 mm (0.030 in.) thick, 300 series stainless steel calorimeter analyzed in Ref (4) has an initial response
time of 72 ms. Eq 2 can be rearranged to show that the initial response time also corresponds to a Fourier Number (a dimensionless
time) of 0.5.
6.3 Conduction heat transfer into the thermocouple wire delays the time predicted by Eq 2 for which the measured back face
temperature rise rate accurately follows (that is, within 1 %) the undisturbed back face temperature rise rate. For a 0.127 mm (0.005
in.) OD, Type K intrinsic thermocouple on a 0.76 mm (0.030 in.) thick, 300 series stainless steel calorimeter, the analysis in Ref
(4) indicates the measured temperature rise rate is within 2 % of the undisturbed temperature rise rate in approximately 500 ms.
An estimate of the measured temperature rise rate error (or slope error) can be obtained from Ref (1) for different material
combinations:
dT dT αt αt
C TC
2 5 C exp C erfcS C D (3)
S D Œ
2 2
1 2 2
dt dt R R
dT dT C αt αt
C TC 2
2 5 C exp *erfcS C ΠD (3)
S D
1 2 2 2
dt dt R R
where:
T = calorimeter temperature,
C
The boldface numbers in parentheses refer to the list of references at the end of this standard.
E459 − 22
T = measured temperature (that is, thermocouple output),
TC
C = β/(8/π + β) and C = 4 ⁄(8 ⁄π + βπ),
1 2
α = k/ρC (thermal diffusivity of the calorimeter material),
p
β =
K/=A ,
K = k of thermocouple wire/k of calorimeter,
A = α of thermocouple wire/α of calorimeter,
R = radius of the thermocouple wire, and
t = time.
Using thermal property values given in Ref (4) for the Alumel (negative) leg of the Type K thermocouple on 300 Series stainless
steel (K = 1.73, A = 1.56, β = 1.39), Eq 3 can be used to show that the measured rate of temperature change (that is, the slope) is
within 5 % of the actual rate of temperature change in approximately 150 ms. For this case, the time for a 1 % error in the measured
temperature rise rate is roughly 50 times as long as the initial response time predicted by Eq 2; this ratio depends on the
thermophysical properties of the calorimeter and thermocouple materials (see Table 1).
6.3.1 When the heat transfer rate varies with time, the thin-skin calorimeter should be designed so the response times defined using
Eq 2 and 3 are smaller than the time for significant variations in the heat transfer rate. If this is not possible, methods for unfolding
the dynamic measurement errors (1, 5) should be used to compensate the temperature measurements before calculating the heat
flux using Eq 1.
6.4 Determine the maximum exposure time (6) by setting a maximum allowable temperature for the front surface as follows:
ρC δ k T 2 T 1
~ !
p max 0
τ 5 * 2 (4)
S D FS D S DG
max
k qδ 3
where:
τ = maximum exposure time, s,
max
T = initial temperature, K, and
T = maximum allowable temperature, K.
max
6.4.1 In order to have time available for the heat transfer rate measurement, τ must be greater thanτthan τ , which requires that:
max Rr
k~T 2 T ! 5
max 0
. (5)
qδ 6
6.4.2 Determine an optimum thickness that maximizes (τ − τ ) (7) as follows:
max Rr
3 k~T 2 T !
max 0
δ 5 (6)
S D
opt
5 q
3 k T 2 T
~ !
max 0
δ 5 * (6)
S D
opt
5 q
6.4.3 Then calculate the maximum exposure time using the optimum thickness as follows:
T 2 T
max 0
τ 5 0.48ρC k (7)
F G
maxopt p
q
T 2 T
max 0
τ 5 0.48ρC k * (7)
F G
maxopt p
q
6.4.4 When it is desirable for a calorimeter to cover a range of heat transfer rates without being operated to burn-out, design the
TABLE 1 Time Required for Different Error Levels in the
Unexposed Surface Temperature Rise Rate
Error Level Due to Heat
Conduction into 10 % 5 % 2 % 1 %
Thermocouple
Negative Leg (Alumel) of 35 ms 150 ms 945 ms 3.8 s
Type K on 304 Stainless
Negative Leg (Constantan) <1 ms <1 ms 1 ms 4 ms
of Type T on Copper
E459 − 22
calorimeter around the largest heat-transfer heat transfer rate. This gives the thinnest calorimeter with the shortest initial response
time (Eq 2); however, Refs (2, 3, 8, 9) all show the time to a given error level between the measured and undisturbed temperature
rise rates (left hand side of Eq 3) increases as the thickness of the calorimeter decreases relative to the thermocouple wire diameter.
6.5 In most applications, the value of T should be well below the melting temperature to obtain a satisfactory design. Limiting
max
the maximum temperature to 700 K will keep radiation losses below 15 kW/m . For a maximum temperature rise (T − T ) of
max 0
400 K, Fig. 2 shows the optimum thickness of copper and stainless steel calorimeters as a function of the heat-transfer heat transfer
rate. The maximum exposure time of an optimum thickness calorimeter for a 400 K temperature rise is shown as a function of the
heat-transfer heat transfer rate in Fig. 3.
6.6 The one-dimensional heat flow assumption used in 2.24.2 and 4.36.3–4.46.4 is valid for a uniform heat-transfer heat transfer
rate; however, in practice, the calorimeter will generally have a heat-transfer heat transfer rate distribution over the surface. Refs
(9, 10) both consider the effects of lateral heat conduction in a hemispherical calorimeter on heat transfer measurements in a
supersonic stream. For a cosine shaped heat flux distribution at the stagnation-point of the hemisphere, Starner (10) gives the lateral
conduction error relative to the surface heating as
2αt 8kt
E 5 5 (8)
C 2 2
L
R ρC D
p
2αt 8kt
E 5 5 (8)
C L 2 2
R ρC D
p
where:
E = relative heat-transfer rate ratio,
R = radius of curvature of the body (D/2), and
t = exposure time.
FIG. 2 Calorimeter Optimum Material Thickness as a Function of Heat Transfer Rate and Material
E459 − 22
FIG. 3 Maximum Exposure Time for an Optimum Thickness Calorimeter as a Function of Heat-Transfer Heat Transfer Rate and Material
FIG. 4 Radial Conduction as a Function of Time and Material
E = relative heat transfer rate ratio,
R = radius of curvature of the body (D/2),
t = exposure time, and
C = centerline.
L
E459 − 22
Note the lateral conduction error described in Eq 8 is not a function of the calorimeter skin thickness or the heat-transfer heat
transfer rate; the magnitude of the error is shown in Fig. 4 for copper and stainless steel. The errors for most other base metal
calorimeters will fall in between these two lines. While the lateral conduction errors can be minimized by using materials with low
thermal diffusivity and short exposure times, these may aggravate some of the other constraints, as described in Eq 2 and 3. Ref
(9) also describes the lateral conduction errors for cones and cylinders.
6.7 An approximation A rough estimate of the lateral conduction error during the test can be obtained experimentally by
continuing to record the unexposed surface temperature after the heating is removed and calculating the ratio of the rates of
temperature change.
dT
cool down
dt
?
E; (9)
test
?
dT
dt
dT dt
cooldown
/
E; (9)
dT dt
/ test
6.8 When the average heat transfer rate over the exposed area is desired, Wedekind and Beck [1989] (11) give another approach
for evaluation of the measured rate of temperature change. The analysis was developed for laser experiments where only part of
the calorimeter surface was exposed to heating and the exposure time was long compared to the thermal penetration time to the
edges of the unexposed area (penetration time calculation is similar to Eq 2 with L, the distance to the edge, substituted for δ, the
thickness).
6.9 A device for recording the thermocouple signals with time is required. The response time (τ ) of an analog recording system
r
should be an order of magnitude smaller than the calorimeter response time (see Eq 2). The sampling time of a digital recording
system should be no more than 40 % of the calorimeter response time; the 3 db 3 db frequency of any low-pass filters in the data
acquisition system should be greater than
1 h
f . 5 (10)
S D
3db
2πτ 2πρC δ
p
1 h
f . 5 (10)
S D S D
3db
2πτ 2πρC δ
r p
where:
h = estimated heat transfer coefficient for the experiment.
7. Hazards
7.1 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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
8. Calibration and Standardization
8.1 It is desirable, but most often not possible, to obtain estimates of the precision and bias of all sensors and instruments. For
example, it is not possible to obtain bias errors for thermocouples mounted on surfaces because the bias errors depend on specifics
of the setup, which varies for each different test. As a result, most often manufacturers provide information for the sensor only.
For example, ASTM’s specifications for thermocouple accuracy are provided in Specification E230 as “tolerances.” An example
for Type K thermocouples is a standard tolerance of “the greater of 62.2 °C or 60.75 % of the reading in °C”. There is no mention
of a precision or bias in that tolerance; it would be very difficult to obtain such numbers. Also, most manufacturers do not provide
an estimate of the confidence level associated with the accuracy specification. For example, one does not often see a specification
like this: the accuracy is 65 % with a confidence level of 95 %. The manufacturer only provides this: the accuracy is 65 %.
Fortunately, many specifications imply the accuracy specification assumes the highest confidence, that is, about 99 %. A detailed
assessment of thermocouple uncertainties, including the data acquisition system, has been documented in Ref. (12).
8.2 Thermocouple Calibration—The user should purchase thermocouples or thermocouple wire from a reputable source and
confirm that the sensors at least meet ASTM tolerances shown in Specification E230. Individual thermocouples can be calibrated
E459 − 22
in a certified laboratory if more accurate values are needed. But those calibrations only apply to a bare wire or shielded
thermocouple not attached to a surface or in a water flow stream. If more information is desired about bias errors, a separate
analysis may be needed on the setup specific to that test. See also Section 13.
8.3 Data Acquisition System Calibration or Verification—The DAS should be on a regularly scheduled re-calibration schedule (for
example, yearly) to check the accuracy of the voltmeter and other parts of the DAS. When used much more
...