ASTM E1311-14(2022)

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: E1311 − 14 (Reapproved 2022)
Standard Practice for
Minimum Detectable Temperature Difference for Thermal
Imaging Systems
This standard is issued under the fixed designation E1311; 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 3.1.2.1 Discussion—The size of the field of view is custom-
arily expressed in units of degrees.
1.1 This practice covers the determination of the minimum
detectable temperature difference (MDTD) capability of a 3.1.3 See also Terminology E1316.
compound observer-thermal imaging system as a function of
4. Summary of Practice
the angle subtended by the target.
4.1 A standard circular target is used in conjunction with a
1.2 The values stated in SI units are to be regarded as
differentialblackbodythatcanestablishoneblackbodyisother-
standard. No other units of measurement are included in this
mal temperature for the target and another blackbody isother-
standard.
mal temperature for the background by which the target is
1.3 This standard does not purport to address all of the
framed. The target, at an undisclosed orientation, is imaged
safety concerns, if any, associated with its use. It is the
onto the monochrome video monitor of a thermal imaging
responsibility of the user of this standard to establish appro-
system whence the image may be viewed by an observer. The
priate safety, health, and environmental practices and deter-
temperature difference between the target and the background,
mine the applicability of regulatory limitations prior to use.
initially zero, is increased incrementally until the observer, in a
1.4 This international standard was developed in accor-
limited duration, can just distinguish the target. This critical
dance with internationally recognized principles on standard-
temperature difference is the MDTD.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom- NOTE 1—Observers must have good eyesight and be familiar with
viewing thermal imagery.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
4.2 The temperature distributions of each target and its
background are measured remotely at the critical temperature
2. Referenced Documents
difference that defines the MDTD.
2.1 ASTM Standards:
4.3 The background temperature and the angular subtense
E1316 Terminology for Nondestructive Examinations
for each target are specified together with the measured value
3. Terminology of MDTD. The (fixed) field of view included by the back-
ground is also specified.
3.1 Definitions:
3.1.1 differential blackbody—an apparatus for establishing 4.4 The probability of detection is specified together with
two parallel isothermal planar zones of different temperatures,
the reported value of MDTD.
and with effective emissivities of 1.0.
5. Significance and Use
3.1.2 field of view (FOV)—the shape and angular dimen-
5.1 This practice gives a measure of a thermal imaging
sions of the cone or the pyramid that define the object space
system’s effectiveness for detecting a small spot within a large
imaged by the system; for example, rectangular, 4-deg wide by
background. Thus, it relates to the detection of small material
3-deg high.
defects such as voids, pits, cracks, inclusions, and occlusions.
This practice is under the jurisdiction of ASTM Committee E07 on Nonde-
5.2 MDTD values provide estimates of detection capability
structive Testing and is the direct responsibility of Subcommittee E07.10 on
that may be used to compare one system with another. (Lower
Specialized NDT Methods.
MDTD values indicate better detection capability.)
Current edition approved Dec. 1, 2022. Published December 2022. Originally
approved in 1989. Last previous edition approved in 2018 as E1311 – 14(2018).
5.3 Due to the partially subjective nature of the procedure,
DOI: 10.1520/E1311-14R22.
repeatability and reproducibility are apt to be poor and MDTD
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
differences less than 0.2 °C are considered to be insignificant.
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. NOTE 2—Values obtained under idealized laboratory conditions may or
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1311 − 14 (2022)
may not correlate directly with service performance.
7.4 Adjust the monochrome video monitor controls so that
the presence of noise is barely perceivable by the observer.
6. Apparatus
7.5 Make the display luminance and the laboratory ambient
6.1 The apparatus consists of the following:
luminance mutually suitable for visual acuity and viewing
6.1.1 Target Plates, containing single or multiple circular
comfort.
targets of area(s) not greater than 5 % of the combined areas of
7.6 Advise the observer that a visible spot will eventually
target and background (that is, FOV area), and with the
appear in the monitor’s display. Instruct him to signal when he
distance from the center of the target to the center of the FOV
can perceive the spot and to cite its orientation relative to the
equal to one third of the height or the diameter of the FOV. See
12 h of a clock; for example, 1 o’clock, 2 o’clock, 3 o’clock,
Fig. 1.
etc. Refrain from further conversation during the procedure
NOTE 3—A target plate may be fabricated by cutting one or more
that could conceivably influence or bias the observer.
circular apertures in a metal plate of high thermal conductivity, such as
aluminum, and coating with black paint of emissivity greater than 0.95. In 7.7 Set∆T (the temperature of the target minus the nominal
this case an aperture would constitute a target, and the coated metal
temperature of the background) equal to zero.
surrounding the target and within the field of view of the thermal imaging
7.8 Increase∆Tin positive increments not exceeding 0.1 °C
system would constitute the target’s background.
every 60 s or until the observer signals. If the identification is
6.1.2 Facility, for mounting targ
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