ASTM E1311-89(2004)
(Test Method)Standard Test Method for Minimum Detectable Temperature Difference for Thermal Imaging Systems
Standard Test Method for Minimum Detectable Temperature Difference for Thermal Imaging Systems
SIGNIFICANCE AND USE
This test method gives a measure of a thermal imaging system’effectiveness for detecting a small spot within a large background. Thus, it relates to the detection of small material defects such as voids, pits, cracks, inclusions, and occlusions.
MDTD values provide estimates of detection capability that may be used to compare one system with another. (Lower MDTD values indicate better detection capability.)
Note 2—Test values obtained under idealized laboratory conditions may or may not correlate directly with service performance.
SCOPE
1.1 This test method covers the determination of the minimum detectable temperature difference (MDTD) capability of a compound observer-thermal imaging system as a function of the angle subtended by the target.
1.2 This standard does not purport to address all of the safety problems, 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
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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:E1311–89(Reapproved 2004)
Standard Test Method 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 framed. The target, at an undisclosed orientation, is imaged
onto the monochrome video monitor of a thermal imaging
1.1 This test method covers the determination of the mini-
system whence the image may be viewed by an observer. The
mum detectable temperature difference (MDTD) capability of
temperature difference between the target and the background,
a compound observer-thermal imaging system as a function of
initially zero, is increased incrementally until the observer, in a
the angle subtended by the target.
limited duration, can just distinguish the target. This critical
1.2 This standard does not purport to address all of the
temperature difference is the MDTD.
safety problems, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
NOTE 1—Observers must have good eyesight and be familiar with
priate safety and health practices and determine the applica- viewing thermal imagery.
bility of regulatory limitations prior to use.
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
of MDTD. The (fixed) field of view included by the back-
3. Terminology
ground is also specified.
3.1 Definitions:
4.4 The probability of detection is specified together with
3.1.1 differential blackbody—an apparatus for establishing
the reported value of MDTD.
two parallel isothermal planar zones of different temperatures,
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 test method 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.
3.1.2.1 Discussion—The size of the field of view is custom-
5.2 MDTD values provide estimates of detection capability
arily expressed in units of degrees.
that may be used to compare one system with another. (Lower
3.1.3 See also Terminology E1316.
MDTD values indicate better detection capability.)
4. Summary of Test Method
NOTE 2—Test values obtained under idealized laboratory conditions
may or may not correlate directly with service performance.
4.1 A standard circular target is used in conjunction with a
differential blackbody that can establish one blackbody isother-
6. Apparatus
mal temperature for the target and another blackbody isother-
6.1 The apparatus consists of the following:
mal temperature for the background by which the target is
6.1.1 Target Plates, containing single or multiple circular
targets of area(s) not greater than 5 % of the combined areas of
This test method is under the jurisdiction of ASTM Committee E07 on
target and background (that is, FOV area), and with the
Nondestructive Testing and is the direct responsibility of Subcommittee E07.10 on
distance from the center of the target to the center of the FOV
Emerging NDT Methods.
equal to one third of the height or the diameter of the FOV. See
Current edition approved May 1, 2004. Published June 2004. Originally
approved in 1989. Last previous edition approved in 1999 as E1311 - 89 (1999). Fig. 1.
DOI: 10.1520/E1311-89R04.
NOTE 3—A target plate may be fabricated by cutting one or more
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
circular apertures in a metal plate of high thermal conductivity, such as
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on aluminum, and coating with black paint of emissivity greater than 0.95. In
the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E1311–89 (2004)
7.8 Increase DT in positive increments not exceeding 0.1°C
every 60 s or until the observer signals. If the identification is
incorrect, continue as before.
NOTE 5—To increase DT it is customary to fix the background
temperature and raise the target temperature.
7.9 If the observer correctly identifies the orientation of the
spot, record the diameter of the target, the diameter or the
height and width of the FOV, and the observation distance
normal to the target plate.
7.10 Measure the temperature distribution of the target and
the target background with an infrared spot radiometer replac-
ing the thermal imaging system. The target shall be measured
in at least three locations, uniformly spaced. The background
shall be measured at two zones: (1) adjacent to the target (that
is, zone 1); (2) beyond zone 1 (that is, zone 2). The measure-
ments in each zone shall be uniformly distributed, with the
number of zone 2 measurements equal to twice that of zone 1
(except for the special case of 7.12).
7.11 Calculate the mean temperature, T, of the target.
Calculate the weighted average, T , of the target background,
B
in accordance with 8.3. Provisionally, DT=T−T is the
B
MDTD. Record DT and T .
B
FIG. 1 Schematic Showing 1. Target Plate; 2. FOV; and 3. Target 7.12 If the target size and the field of view of the spot
radiometer are comparable, make double the number of zone 2
measurements, in pairs consisting of two adjacent locations.
Compare adjacent temperature readings; the difference be-
this case an aperture would constitute a target, and the coated metal
surrounding the target and within the field of view of the therma
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.