understanding infrared thermography reading 5

Infrared Thermal TestingReading VMy ASNT Level III, My Pre-Exam Preparatory Self Study Notes 9 June 2015

Charlie Chong/ Fion Zhang

Military Applications


Fire & Rescue Applications


The Magical Book of Infrared Thermography



Reading VContent Reading One: Level I/II/III Q&A Reading Two: Reading Three:

Fion Zhang at Shanghai9th June 2015

http://meilishouxihu.blog.163.com/


Charlie Chong/ Fion Zhang http://greekhouseoffonts.com/


Notation:h = Plank’s constantσ = Stephen-Boltzmann constantα = absorptivityε = emissivityρ = reflectivityτ = transmissivity


IVONA TTS Capable.

http://www.naturalreaders.com/


Infrared Spectrum


Wavelength segmentation

Infrared technologies spectrum range from NIR to LWIR wavelengths. Each part of the spectrum provides different information and hence targets different markets: • NIR (Near IR) – SWIR : active vision enhancement (need an NIR light source), high temperature thermography, material

analysis • MWIR (Medium Wave IR): thermography, passive vision enhancement, material analysis • LWIR (Long Wave IR) called also FIR (Far IR): Thermography and passive vision enhancement (no need for light source)


FLIR-K-Series Thermal Cameras for Firefighting

■ https://www.youtube.com/embed/lClR9o6koi0

https://www.youtube.com/watch?v=lClR9o6koi0


"Infrared Camera Inspection for Home Inspectors"homes with an infrared camera with Ben Gromicko.

■ http://fast.wistia.net/embed/iframe/mgz9l0il0e

http://www.nachi.org/inspection-video-infrared-camera-inspection.htm


Reading OneThermal & Infrared Testing


Level I Q&A


1. One calorie is equivalent to how much heat energy? a. raising the temperature of 1 lb of water 1 ºF (Btu?)b. raising the temperature of 1 g of water 1ºC c. raising the temperature of 1 lb of water 1 ºC d. raising the temperature of 1 g of water 1 ºF

2. Which of the following is incorrect? a. 0 ºC = 32 ºF b. -40 ºC = -40 ºF c. ºC = 32 + (9/5 x ºF) (?)d. 100 ºC = 212 ºF

Fº = 32+(Cº x 9/5)Cº = (Fº -32) x 5/9

http://fahrenheittocelsius.com/


3. Newton's Law of convective cooling states that: a. the rate of heat loss is proportional to the heat capacity of the body

and its surface area b. the rate of cooling is inversely proportional to the temperature c. the rate of heat loss is inversely proportional to the temperature of the

body d. the rate of heat loss of a body is proportional to the difference in

temperature between the body and its fluid surroundings. dQ/dt = h∙A(TB-TS)

4. The second law of thermodynamics states: a. energy moving into a body equals the energy leaving a body if it is at

steady state b. energy moves from areas of high temperature to areas of low

temperature c. energy moves from cooler areas to warmer areas d. energy moving out of a body equals the energy transmitting through the

body


5 . The first law of thermodynamics states:a. when energy moving into a body plus any internal energy generated

equals the energy leaving a body, that body is in a steady state condition

b. energy moves from areas of high temperature to areas of low temperature c. energy moves from cooler areas to warmer areas d. energy moving out of a body equals the energy transmitting through the

body.

6. Which of the following temperature scales is considered an absolute scale?

a. Fahrenheit b. Boltzmann c. Celsius d. kelvin


Newton’s law of cooling

In science, Newton’s law of cooling states that the rate of heat loss dQ of a body is proportional to the difference in temperatures between the body and its surroundings, as shown below:

dQ/dt = h∙A(TB-TS)

where h is the (convective) heat transfer coefficient, A is the unit surface area of the body through which the heat is transferred, TB is the temperature of the surface of the body (solid), and TS is the temperature of the surroundings (fluid).

Newton’s law of cooling is generally limited to simple cases where the mode of energy transfer is convection, from a solid surface to a surrounding fluid in motion, and where the temperature difference is small, approximately less than 10º C. When the medium into which the hot body is placed varies beyond a simple fluid, such as in the case of a gas, solid, or vacuum, etc., this becomes a residual effect requiring further analysis.


Q7. Which of the following temperature scales is considered to be a relative scale?a. Rankineb. Boltzmannc. Celsiusd. kelvin

Q8. For every degree on the Celsius temperature scale how many degrees are on the Fahrenheit scale?a. 5/9 - 32b. 1.8c. 32d. 1000.356


Q9. The material property that relates to the rate that heat flows though a solidmaterial is called:a. thermal conductivityb. convective efficiencyc. conductive efficiencyd. emissive conductivity

Q10. A micron is a unit of:a. lengthb. wave amplitudec. temperatured. roughness


Q11. A micron is a unit of measure that is:a. one thousandth of a meterb. one thousand thousandth of a inchc. one millionth of a meterd. one millionth of an inch

Q12. Which material below is transmissive to long wave (8-14 μm) infrared radiation?a. polyethylene filmb. glass (good till 5μm)c. rubberd. human skin

Wave Number = 1/λ (λ = 8 - 14 μm ↔ n=1250 ~ 714 cm-1)


HDPE IR Transmittance Spectrum

HDPE is opaque at this spectra bend width, τ = 0


■ωσμ∙Ωπ∆º≠δ≤>ηθφФρ|β≠Ɛ ʋ ∠ λ α ρτ


IR Transmittance Spectrum for PU


IR Transmittance Spectrum for Fused Silica


IR Transmittance Spectrum for Borosilicate


IR Transmittance Spectrum for Fused Silica


Q13. You are inspecting an energized 440 V electrical three-phase fused disconnect. The fuse caps on the fuses are copper and appear cooler than the fuse cardboard bodies. What is probably the reason?a. the fuse caps are emitting the coolness inside themselvesb. the fuse caps are radiating less energy and reflecting the cooler room temperaturesc. the fuse bodies are actually warmer than the fuse capsd. the fuse bodies are reflecting your body's warmth

Q14. Emittance of a surface may vary with which of the following?a. thermal conductanceb. angle of viewc. thermal resistanced. coefficient of convective heat transfer


Q15. A low sloped roof is inspected in the early evening after a sunny day. Wet absorbent roof insulation appears warmer than the dry insulation because:a. the wet insulation is a better emitter of thermal radiationb. the wet insulation is more reflective than the dry insulationc. the dry insulation cools off slower than the wet insulationd. the wet insulation cools off slower than the dry insulation

Q16. Which of the following equations is used to calculate the amount of radiant energy emitted from a surface?a. R+A+T= 1b. Q = σeT4

c. μm = b/T absoluted. E = mc2


Q17. Which of the following IR camera settings may affect a radiometric temperature measurement?a. spanb. levelc. paletted. focus

Q18. Which of the following camera parameters is not adjustable in post- processing computer software?a. spanb. levelc. emissivityd. range


Q19. A thick ceramic coffee mug has an emissivity of 0.84 in the 8 - 14 μm wave band. What is its reflectivity?a. 0.84b. 0.48c. 0.34d. 0.16

Q20. The temperature of an aluminum bus bar is being measured. You have determined emissivity is 0.15. What is the reflectivity of the bus bar? a. 0.0b. 0.15c. 0.85d. 1.0


21. A perfect thermal mirror would bave an emittance equal to:a. 0.0b. 0.01c. 0.5d. 1.0

22. Thermal infrared radiation occurs at wavelengths:a. shorter than X-raysb. shorter than visible lightc. longer than visible lightd. longer than radio waves


23. An opaque graybody surface with an emissivity of 0.04 would be:a. transparent to infrared radiationb. a fairly good emitterc. almost a perfect reflectord. almost a perfect emitter

24. The radiant energy emitted by an object is a function of what power of its absolute temperature?a. first powerb. second powerc. third powerd. fourth power


25. What are the three modes of heat transfer?a. reflected, transmitted, emittedb. conductive, convective, radiativec. absorption, emission, transmissiond. temperature, thermal movement, absorbency

26. A quick and simple technique for improving the emissivity of highly reflective surfaces is to: a. use a shorter wavelength infrared camerab. apply black electrical tape to the surfacec. cover the surface with aluminum foild. adhere black thin film polyethelene


27. What can we say for certain about a clear piece of thin plastic?a. it is transparent to infraredb. it is opaque to infraredc. its emissivity is less than 1d. its reflectivity is more than 1

28. A large variance of the viewing angle from the normal (90°) to a non- metallic surface of interest _______the emitted energy sensed.a. decreasesb. increases linearlyc. increases exponentiallyd. has no effect on


29. In an infrared roof moisture survey, what effects cause the areas of roof over wet insulation to be warmer at night than those over dry insulation? a. high heat capacity of water and daytime insolationb. increase thermal resistance of wet insulationc. warmer evening temperatures combined with cooler interior temperaturesd. lower heat capacity of water and cooler evening temperatures

30. Which of the following is not a typical pattern of an anomalous thermal image associated with wet roof insulation?a. circularb. amorphousc. picture framed. board type


Q31. What does IFOV stand for?a. increasing field of viewb. instantaneous field of viewc. infringing field of viewd. image field of view

Q32. At what temperature does the emittance of thermal radiation begin?a. above - 273 Kb. at 0ºCc. above 0Kd. above -460 R


Q33. Why do a block of wood and a piece of steel at the same temperature feel so different when they come into contact with your body?a. the thermal conductivity of the steel is greaterb. the thermal conductivity of the wood is greaterc. the wood is a much better emitter than the steeld. the steel is heavier than the wood

Q34. During the summer with clear sunny days, clear nights and a diurnal 一日间的 / 昼行性的 temperature swing from 32 °C (90 °F) to 10 °C (50 °F), a lake and the surrounding land would probably have the following thermal relationship:a. the land would be cooler than the lake at nightb. the land would be warmer than the lake during the daytimec. the land would be warmer than the lake day and nightd. the land would be cooler earlier in the evening then become warmer by morning


Q35. The ratio of the radiant emittance of a given body to that of a black body is defined as:a. radiance b. reflectivityc. emissivityd. transmissivity

Q36. Which of the following has the lowest conductivity?a. Aluminumb. Steelc. Woodd. Copper


Q37. Which of the following camera adjustment is use to optimize thermal contrast of a thermal image?a. focusb. span (temperature display span)c. level (mid point of a temperature span)d. range (temperature range with FOV?)

Q38. Which of the following camera adjustment will has effect on temperature measurement?a. focus (increase the thermal sensitivity)b. spanc. level d. palette


39. Which of the following is a commonly used technique to increase contrast in thermal images?a. adjust camera to a higher temperature rangeb. increase the span setting of the thermal imagec. use a gray monochrome paletted. change to a multi-division calor palatte such as a rainbow (?)

40. Periodically most focal plane array thermal imagers pause the live image and go through an internal routine called what?a. non-uniformity correction (?)b. internal temperature calibrationc. thermal temperature correctiond. temperature uniformity calibration


Q41. An appropriate thermal span and level setting for imaging a human face in a 22 °C (72 °F) room is:a. 37 °C (98.6 °F)b. 27 to 38 °C (80 to 100 °F)c. 35 to 43 °C (95 to 110 °F)d. 13 to 22 °C (55 to 72 °F)


More Reading Before Cruising Level II


More Reading on: Thermographic camera A thermographic camera (also called an infrared camera or thermal imaging camera) is a device that forms an image using infrared radiation, similar to a common camera that forms an image using visible light. Instead of the 450–750 nanometer range of the visible light camera, infrared cameras operate in wavelengths as long as 14,000 nm (14 µm). Their use is called thermography.

Image of a small dog taken in mid-infrared ("thermal") light (false-color)

450–750 nanometer = 0.45μm ~ .75 μm

https://en.wikipedia.org/wiki/Thermographic_camera


History Precursors Infrared was discovered by Sir William Herschel as a form of radiation beyond red light. These "infrared rays" (infra is the Latin prefix for "below") were used mainly for thermal measurement. There are four basic laws of IR radiation: ■ Kirchhoff's law of thermal radiation, ■ Stefan-Boltzmann law, ■ Planck’s law, and ■ Wien’s displacement law.

The development of detectors was mainly focused on the use of thermometer and bolometers until World War I. Leopoldo Nobili fabricated the first thermocouple in 1829, which paved the way for Macedonio Melloni to show that a person 10 meters away could be detected with his multi-element thermopile. The bolometer was invented in 1878 by Langley. It had the capability to detect radiation from a cow from 400 meters away, and was sensitive to differences in temperature of one hundred thousandth of a degree Celsius (.001ºC).



The first advanced application of IR technology in the civil section may have been a device to detect the presence of icebergs and steamships using a mirror and thermopile, patented in 1913. This was soon outdone by the first true IR iceberg detector, which did not use thermopiles, patented in 1914 by R.D. Parker. This was followed up by G.A. Barker’s proposal to use the IR system to detect forest fires in 1934. The technique was not truly industrialized until it was used in the analysis of heating uniformity in hot steel strips in 1935.



First thermographic camera In 1929, Hungarian physicist Kálmán Tihanyi invented the infrared-sensitive (night vision) electronic television camera for anti-aircraft defense in Britain. The first thermographic cameras began with the development of the first infrared line scanner. This was created by the US military and Texas Instruments in 1947 and took one hour to produce a single image. While several approaches were investigated to improve the speed and accuracy of the technology, one of the most crucial factors dealt with scanning an image, which the AGA company was able to commercialize using a cooled photoconductor.

This work was further developed at the Royal Signals and Radar Establishment in the UK when they discovered mercury cadmium telluride could be used as a conductor that required much less cooling. Honeywell in the United States also developed arrays of detectors which could cool at a lower temperature, but they scanned mechanically. This method had several disadvantages which could be overcome using an electronically scanning system. In 1969 Michael Francis Tompsett at English Electric Valve Company in the UK patented a camera which scanned pyro-electronically and which reached a high level of performance after several other breakthroughs throughout the 1970s. Tompsett also proposed an idea for solid-state thermal-imaging arrays, which eventually led to modern hydridized (?) single-crystal-slice imaging devices



Smart sensors One of the most important areas of development for security systems was for the ability to intelligently evaluate a signal, as well as warning for a threat's presence. Under the encouragement of the United States Strategic Defense Initiative, "smart sensors" began to appear. These are sensors that could integrate sensing, signal extraction, processing, and comprehension. There are two main types of Smart Sensors. One, similar to what are called "vision chips" when used in the visible range, allow for preprocessing using Smart Sensing techniques due to the increase in growth of integrated microcircuitry. The other technology is more oriented to a specific use and fulfills its preprocessing goal through its design and structure.

Towards the end of the 1990s the use of infrared was moving towards civil use. There was a dramatic lowering of costs for uncooled arrays, which along with the large increase in developments lead to a dual way use market between civil and military. These uses include environmental control, building/art analysis, medical functional diagnostics, and car guidance and collision avoidance systems.



Theory of operationA thermal image showing temperature variation in a hot air balloon.Infrared energy is just one part of the electromagnetic spectrum, which encompasses radiation from gamma rays, x-rays, ultra violet, a thin region of visible light, infrared, terahertz waves (?) , microwaves, and radio waves. These are all related and differentiated in the length of their wave (wavelength λ). All objects emit a certain amount of black body radiation as a function of their temperatures (?) .

Generally speaking, the higher an object's temperature, the more infrared radiation is emitted as black-body radiation. A special camera can detect this radiation in a way similar to the way an ordinary camera detects visible light. It works even in total darkness because ambient light level does not matter. This makes it useful for rescue operations in smoke-filled buildings and underground.



A thermal image showing temperature variation in a hot air balloon.



In use Thermographic image of a ring-tailed lemur Images from infrared cameras tend to have a single color channel because the cameras generally use an image sensor that does not distinguish different wavelengths of infrared radiation. Color image sensors require a complex construction to differentiate wavelengths, and color has less meaning outside of the normal visible spectrum because the differing wavelengths do not map uniformly into the system of color vision used by humans.

Sometimes these monochromatic images are displayed in pseudo-color, where changes in color are used rather than changes in intensity to display changes in the signal. This is useful because although humans have much greater dynamic range in intensity detection than color overall, the ability to see fine intensity differences in bright areas is fairly limited. This technique is called density slicing.



Keywords:Density Slicing - False color (or false colour) refers to a group of color rendering methods used to display images in color which were recorded in the visible or non-visible parts of the electromagnetic spectrum. A false-color image is an image that depicts an object in colors that differ from those a photograph (a "true-color" image) would show.

In addition variants of false color such as pseudocolor (see discussion), density slicing (see discussion), and choropleths (see discussion) are used for information visualization of either data gathered by a single grayscale channel or data not depicting parts of the electromagnetic spectrum (e.g. elevation in relief maps or tissue types in magnetic resonance imaging).



Density slicing, a variation of pseudo color, divides an image into a few colored bands and is (among others) used in the analysis of remote sensing images. For density slicing the range of grayscale levels is divided into intervals, with each interval assigned to one of a few discrete colors – this is in contrast to pseudo color, which uses a continuous color scale. For example, in a grayscale thermal image the temperature values in the image can be split into bands of 2 °C, and each band represented by one color – as a result the temperature of one spot in the thermograph can be easier acquired by the user, because the discernible differences between the discrete colors are greater than those of images with continuous grayscale or continuous pseudo color.



Density Slicing- a variation of pseudo color, divides an image into a few colored bands and is (among others) used in the analysis of remote sensing images. For density slicing the range of grayscale levels is divided into discrete intervals (discrete colors or gray scale) , with each interval assigned to one of a few discrete colors – this is in contrast to pseudo color, which uses a continuous color scale.

An image of Tasmania and surrounding waters using density slicing to show phytoplankton concentration. The ocean color as captured by the satellite image is mapped to seven colors: Yellow, orange and red indicate more phytoplankton, while light green, dark green, light blue and dark blue indicate less phytoplankton; land and clouds are depicted in different colors.

https://en.wikipedia.org/wiki/False_color#Density_slicingc


Thermographic image of a ring-tailed lemur



Ring-tailed lemur



For use in temperature measurement the brightest (warmest) parts of the image are customarily colored white, intermediate temperatures reds and yellows, and the dimmest (coolest) parts black. A scale should be shown next to a false color image to relate colors to temperatures. Their resolution is considerably lower than that of optical cameras, mostly only 160 x 120 or 320 x 240 pixels, although more expensive cameras can achieve a resolution of 1280 x 1024 pixels.[23] Thermographic cameras are much more expensive than their visible-spectrum counterparts, though low-performance add-on thermal cameras for smartphones became available for hundreds of dollars in 2014.

Higher-end models are often deemed as dual-use and export-restricted, particularly if the resolution is 640 x 480 or greater, unless the refresh rate is 9 Hz or less. The export of thermal cameras is regulated by International Traffic in Arms Regulations, or ITAR. All FLIR VOx microbolometers are restricted to 7.5 Hz for export outside of the US.



Add-on thermal cameras for smartphones became available for hundreds of dollars in 2014. (Flir-One for Iphone)

http://www.clubic.com/salon-informatique-tic/ces/actu-ces_2014_flir_one_pour_changer_son_iphone_en_camera_thermique-611622.html




DiscussionSubject: “Higher-end models are often deemed as dual-use and export-restricted, particularly if the resolution is 640 x 480 or greater, unless the refresh rate is 9 Hz or less. The export of thermal cameras is regulated by International Traffic in Arms Regulations, or ITAR. All FLIR VOx microbolometers are restricted to 7.5 Hz for export outside of the US.”

Question: what is the significant of refresh rate?



Movies Time- Fun Time Flir Camera

■ https://www.youtube.com/embed/yFo_MN_QCwE

http://www.lapolicegear.com/flir-ps24-flir--ps24.html


In uncooled detectors the temperature differences at the sensor pixels are minute; a 1 °C difference at the scene induces just a 0.03 °C difference at the sensor. The pixel response time is also fairly slow, at the range of tens of milliseconds.

Thermography finds many other uses. For example, firefighters use it to see through smoke, find people, and localize hotspots of fires. With thermal imaging, power line maintenance technicians locate overheating joints and parts, a telltale sign of their failure, to eliminate potential hazards. Where thermal insulation becomes faulty, building construction technicians can see heat leaks to improve the efficiencies of cooling or heating air-conditioning.

Thermal imaging cameras are also installed in some luxury cars to aid the driver (Automotive night vision), the first being the 2000 Cadillac DeVille.

Some physiological activities, particularly responses such as fever, in human beings and other warm-blooded animals can also be monitored with thermographic imaging. Cooled infrared cameras can be found at major astronomy research telescopes, even those that are not infrared telescopes.



Types Thermographic cameras can be broadly divided into two types: those with cooled infrared image detectors and those with uncooled detectors.

■ Cooled infrared detectors Thermal imaging camera & screen, in an airport terminal in Greece. Thermal imaging can detect fever, one of the signs of infection. Cooled detectors are typically contained in a vacuum-sealed case or Dewar and cryogenically cooled. The cooling is necessary for the operation of the semiconductor materials used. Typical operating temperatures range from 4 K to just below room temperature, depending on the detector technology. Most modern cooled detectors operate in the 60 K to 100 K range, depending on type and performance level. Without cooling, these sensors (which detect and convert light in much the same way as common digital cameras, but are made of different materials) would be 'blinded' or flooded by their own radiation. The drawbacks of cooled infrared cameras are that they are expensive both to produce and to run. Cooling is both energy-intensive and time-consuming. The camera may need several minutes to cool down before it can begin working. The most commonly used cooling systems are rotary Stirling engine cryocoolers. Although the cooling apparatus is comparatively bulky and expensive, cooled infrared cameras provide superior image quality compared to uncooled ones.



Thermal imaging camera & screen, in an airport terminal in Greece. Thermal imaging can detect fever, one of the signs of infection.



Additionally, the greater sensitivity of cooled cameras also allow the use of higher F-number lenses, making high performance long focal length lenses both smaller and cheaper for cooled detectors. An alternative to Stirling engine coolers is to use gases bottled at high pressure, nitrogen being a common choice. The pressurised gas is expanded via a micro-sized orifice and passed over a miniature heat exchanger resulting in regenerative cooling via the Joule–Thomson effect. For such systems the supply of pressurized gas is a logistical concern for field use.

Materials used for cooled infrared detection include photodetectors based on a wide range of narrow gap semiconductors including:



■ indium antimonide (3-5 μm)■ indium arsenide■ mercury cadmium telluride (MCT) (1-2 μm, 3-5 μm, 8-12 μm)■ lead sulfide■ lead selenide

Infrared photodetectors can be created with structures of high band gap semiconductors such as in Quantum well infrared photodetectors.

A number of superconducting and non-superconducting cooled bolometer technologies exist.

In principle, superconducting tunneling junction devices could be used as infrared sensors because of their very narrow gap. Small arrays have been demonstrated. Their wide range use is difficult because their high sensitivity requires careful shielding from the background radiation. Superconducting detectors offer extreme sensitivity, with some able to register individual photons. For example ESA's Superconducting camera (SCAM). However, they are not in regular use outside of scientific research.



Hot hooves indicate a sick cow



A thermographic image of a snake around an arm



A thermographic image of several lizards



Uncooled infrared detectors Uncooled thermal cameras use a sensor operating at ambient temperature, or a sensor stabilized at a temperature close to ambient using small temperature control elements. Modern uncooled detectors all use sensors that work by the change of (1) resistance, (2) voltage or (3) current when heated by infrared radiation. These changes are then measured and compared to the values at the operating temperature of the sensor.

Uncooled infrared sensors can be stabilized to an operating temperature to reduce image noise, but they are not cooled to low temperatures and do not require bulky, expensive cryogenic coolers. This makes infrared cameras smaller and less costly. However, their resolution and image quality tend to be lower than cooled detectors. This is due to difference in their fabrication processes, limited by currently available technology.

Uncooled detectors are mostly based on (1) pyroelectric and (2) ferroelectric materials or (3) microbolometer technology. The material are used to form pixels with highly temperature-dependent properties, which are thermally insulated from the environment and read electronically.



Ferroelectric detectors operate close to phase transition temperature of the sensor material; the pixel temperature is read as the highly temperature-dependent polarization charge. The achieved NETD (noise equivalent temperature difference) of ferroelectric detectors with f/1 optics and 320x240 sensors is 70-80 mK. A possible sensor assembly consists of barium strontium titanate bump-bonded by polyimide thermally insulated connection.

Silicon microbolometers can reach NETD down to 20 mK. They consist of a thin film vanadium(V) oxide (VOx) sensing element suspended on silicon nitride bridge above the silicon-based scanning electronics. The electric resistance of the sensing element is measured once per frame.

Current improvements of uncooled focal plane arrays (UFPA) are focused primarily on higher sensitivity and pixel density. In 2013 DARPA announced a five-micron LWIR camera that uses a 1280 x 720 focal plane array (FPA). Some of the materials used for the sensor arrays are:



• vanadium(V) oxide (metal insulator phase change material, for microbolometer arrays)

• lanthanum barium manganite (LBMO, metal insulator phase change material)

• amorphous silicon• lead zirconate titanate (PZT)• lanthanum doped lead zirconate titanate (PLZT)• lead scandium tantalate (PST)• lead lanthanum titanate (PLT)• lead titanate (PT)• lead zinc niobate (PZN)• lead strontium titanate (PSrT)• barium strontium titanate (BST)• barium titanate (BT)• antimony sulfoiodide (SbSI)• polyvinylidene difluoride (PVDF)



Applications Originally developed for military use during the Korean War, thermographic cameras have slowly migrated into other fields as varied as medicine and archeology. More recently, the lowering of prices have helped fuel the adoption of infrared viewing technology. Advanced optics and sophisticated software interfaces continue to enhance the versatility of IR cameras.

■ Night vision■ Building inspection

• Energy auditing of building insulation and detection of refrigerant leaks• Roof inspection• Home performance• Moisture detection in walls & roofs (and thus in turn often part of mold

remediation)• Masonry wall structural analysis



■ Law enforcement and anti-terrorism • Quarantine monitoring of visitors to a country• Military and police target detection & acquisition: Forward looking

infrared, Infra-red search and track• Condition monitoring & surveillance• Technical surveillance counter-measures• Thermal weapon sight• Search and rescue operations• Firefighting operations

■ Thermography (medical) • Medical testing for diagnosis Veterinary thermal imaging

■ Program process monitoring • Quality control in production environments• Predictive maintenance (early failure warning) on mechanical &

electrical equipment



• Astronomy, in devices such as the Spitzer Space Telescope• Automotive night vision• Auditing of acoustic insulation for sound reduction• Chemical imaging• Nondestructive testing• Research & development of new products• Pollution effluent detection• Locating unmarked graves• Locating pest infestations• Aerial archaeology• Paranormal investigation• Flame detector• Meteorology (thermal images from weather satellites are used to

determine cloud temperature/height and water vapor concentrations, depending on the wavelength)

• Cricket Umpire Decision Review System. To detect faint contact of the ball with the bat (and hence a heat patch signature on the bat after contact)



Specifications Some specification parameters of an infrared camera system are:

• Number of pixels• Frame rate• Noise-equivalent temperature difference (NETD)• Spectral band• Distance-to-Spot Ratio (D:S)• Minimum Focus Distance• Sensor lifetime• Minimum resolvable temperature difference (MRTD)• Field of view• Dynamic range• Input power• Mass and volume



The thermographic camera on a Eurocopter EC 135 helicopter of the German Federal Police.



More Reading with subject relating to Rainbow Palette Camera Characteristic: Range Span / Level Focus Palette (color palette?)

Others Characteristic: NUC (Non Uniform Correction)


1. IR Camera- Span & LevelIn thermography, “Span” refers to the difference between the high and low temperature settings on an infrared image.“Level” is the mid-point of that span.

Let me use an example to help further explain this.All Fluke thermal imagers can be set to either auto or manual span control. In the auto mode, the camera automatically sets the span to the highest and lowest temperatures within the (FOV) Field of View (Figure 1). In manual mode, the user can define the highest and lowest temperatures of the span (Figure 2).

http://thermal-imaging-blog.com/index.php/2010/02/10/level-and-span-a-definition/


In auto mode, Figure 1 shows the camera with a span of 31°F from a range of 64°F to 95°F. The area of interest is the potential insulation issue seen just above the window curtain (lighter colored area on the ceiling). While we can partially see this potential problem, the issue is somewhat masked due to the higher temperature light fixture on the left wall in the field of view (FOV).

Taking advantage of the “manual mode” we can remove or “saturate out” the higher and lower temperatures not associated with the area of interest, in this case the light on the left. Doing so improves the clarity of the thermal image allowing us to better highlight the insulation issue. This new “thermal window” or defined span within the image offers more detail and can then be adjusted up or down to accommodate the changing scene within the field of view.

Again, a wide span gives less detail and a narrow span offers more detail in the image. According to “best practice” in thermography, keep your span as narrow as possible and adjust the level as needed.

http://thermal-imaging-blog.com/index.php/2010/02/10/level-and-span-a-definition/


Span & LevelSame spend at 2 different levels.

140ºC 40ºC

Span of 100ºC at Level 40ºC

Span of 100ºC at Level 140ºC

Range


2. IR Camera FocusIf we think about visual photography for a minute, what comes to mind when you have a picture that is not in focus? Can you pick out the details that are important to you, does it look good, and can you see the trees from the forest? Generally we toss those bad, out of focus images in favor of the good ones—and this is true with thermal images as well.

Even more important, an infrared thermal image that is out of focus also displays bad temperature data. Note the “out of focus” image in Figure 1 and note the temperature of the center point. Compare it to the image in Figure 2, an “in focus” image. Quite a difference–and that difference could lead you to an incorrect conclusion!

Focusing a scene or object using an infrared camera is more problematic than what you might be used to using on your visual light camera. In the world of “visual light” we can take advantage of reflected light which creates share distinction between objects. In thermography, we need to deal with energy that is emitted from the surface and those “pesky” three modes of heat transfer. As heat energy moves through solids, liquids and gasses, those crisp lines between objects disappear, making focus a challenge.


IR Camera Focus

362.2 ºC 383.8 ºC


There are a few simple suggestions to help, such as:

• The human eye most often can focus in black and white (gray scale) easier than other color scales

• Look for a sharp edge that you see in the field of view • Hold the camera still • Practice! • And with Fluke infrared camera you can effectively use “IR-Fusion”

Using Fluke’s IR-Fusion in the picture-in-picture mode, you can see the two images (visible and IR) slide up and down independently. When the two line up, you are perfectly in focus!

In summary, the focus of any image is important both for clarity & accuracy of data and for the ability for others to see what is the focus of the image. Practice using any and all for the available pallets, and that will—as the saying goes—“make perfect” the image!


Span & Level


3. Color Palette We have already talked about what are and how thermal cameras work, but now it is time to do a quick look at what do thermal images look like usually. Thermal cameras do not actually detect color as the infrared range they operate in is way beyond the range of the visible light, instead they record thermal information and that thermal information is then displayed in a way that we can visually interpret it in the form of an image. To make it easier for people to easily analyze a thermal image visually it is represented using a false colors representing the difference in temperature and the most commonly used color palette for that is the so called Iron one (shown above) where black is for the coldest areas, then blue and purple for slightly hotter areas, the mid-range of temperatures is usually red, orange and yellow and then going to white for the hottest parts. These false color visualizations usually do come with a small scale next to the image that show the colors used and what temperature range they cover as otherwise the person seeing a thermal image may get the wrong idea about the actual object temperature. It all depends on the temperature range that has been recorded, so black (the coldest part) on a thermal image can represent 0 degrees Celsius, 23.5 degrees C or another value and the same goes for the hottest and whitest part it could be 62.3 degrees Celsius or 200 degrees C. In thermal images using false colors to represent the difference in temperature there is no specific temperature representing specific color from the color palette used, the colors are just there to make it easy to distinguish the coldest from the hottest parts.

http://thermalimaging-blog.com/tag/rainbow-palette/


Iron One- the most commonly used color palette for that is the so called Iron one



Another very common way is to represent a thermal image is in the form of a grayscale image, where you get only black to white colors passing through various levels of gray to represent the difference in temperature. This way of representing thermal images is often used in thermal security cameras or night vision thermal devices, but you will probably see it rarely used in other areas when thermal cameras are needed. The reason for that is, because it is harder for a normal person to distinguish the difference in temperature when only a single color is used and only the level of intensity is varied. It is much easier when you use a color palette with multiple colors. Aside from the most common Iron color palette that we’ve shown to you above here you can see some of the other often used false color representations used for thermal images.


Charlie Chong/ Fion Zhang http

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agin

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These are the:■ Grayscale palette that we’ve already discussed as well as ■ Arctic, ■ Lava and ■ Rainbow, (discrete color not continuous, ≠ pseudo color)

and you may also find a versions of these with higher contrasting color palettes to make differences even more apparent.

There of course could be thermal images using different color palettes as well, but as long as you have the smaller scale with the used colors and what temperatures they represent you should be able to quickly get an idea on what you are seeing in terms of temperature. Another interesting way of focusing the viewer’s attention to a specific area of the thermal image is to use grayscale thermal image with color only on specific areas that are either below or above certain temperature or if they fit in a specified thermal range.



4. Infrared Tip - Considerations for Color PalettesMatt Schwoegler, The Snell Group

“What’s the best color palette to use?” is a question commonly heard during an infrared training course. To be honest, this can depend on the application, but many times it is also about the personal preferences of the thermographer. In my experience as an instructor, however, I have found that two considerations always seem to stand out when answering this question, both of which provide a good guideline to follow when deciding what type of color palette to use.

1) The Color Palette Facilitates Focus

First, and most importantly, a color palette should give you the best ability to focus. Typically a Grayscale, or more monochromatic type color palette (Amber, Hot Metal or Iron/Ironbow), can be easier to use when focusing a thermal image. Take a look at these two examples, each saved with a different color palette, and see if you can tell which has the better focus or, for that matter, which looks sharper?

http://www.thesnellgroup.com/Content/infrared-tip-considerations-for-color-palettes.aspx


Rainbow – facilitate temperature differentiation

Gray-scale – facilitate focusing



Answer? The focus is actually identical because both of them originate from the same raw data file. The only difference is that it was exported twice in the software, once with a Grayscale palette and once more in Rainbow. The Rainbow color palette on the left, however, has too much contrast making it more difficult to find the exact focus point along edges of objects. The colors just blend together, masking edge details of the window trim and siding that one would typically look to when adjusting the sharpness of the picture. In the Grayscale version, the outlines of the trim and siding are more easily seen, facilitating focus.

Images that are poorly focused are of not much value to you, your clients or your infrared program as it can affect your ability to properly evaluate thermal anomalies. Remember, you can always change the color palette after you have captured an image, either in the camera (on most models) or in the software provided, but you can never change the focus of a saved image. Focus also impacts the accuracy of temperature measurements too as seen in these examples:



Notice in the properly focused image (above left) that the box temperature, set to “Area Max”, reads 266 °F (130 °C). That same box temperature, however, in the out of focus image on the right reads only 189.9 °F (87.7 °C) a difference of 76.1 °F (42.3 °C)! Know that as your distance increases, this effect only gets worse where being just the slightest bit out of focus can have an even larger impact on temperature values.



Keypoints:• Focus affecting the accuracy of temperature measurement• Gray scale help in correct focusing• Rainbow color palette (density slicing) help in differentiating temperature

differences.



2) It is Intuitive and Easy to Use The other consideration is that color palettes should be intuitive 直观的 and easy to decipher at any given instant when working in the field. I find this is often difficult to achieve when using a Rainbow or High Contrast color palette (although some may disagree, but again, that comes back to personal preference). Grayscale, or a more monochromatic color palette such as Amber (or even Ironbow) can be interpreted easily by thermographers of any skill level. There is no question as to what is the hottest color gradient in the image. Lighter is warmer, darker is cooler.

With rainbow-like palettes I find that thermographers, especially those who are new to the technology, are often confused with the question of “Is red warmer than yellow or is light blue cooler than dark green?” For those that may have an eye color deficiency, the challenge of using rainbow is heightened even further and should be avoided. Also consider your reports and who might be reading them as they may have a color deficiency too.

If you do choose to work in Rainbow, however, it seems reasonable that one could simply look at the scale to get the answer of which color is warmer than another. I would argue, though, that a good color palette should be intuitive and not require having to look in the first place. Just asking that in your head, while taking your eyes off the target, is an unnecessary distraction in my opinion. Why make it harder than it needs to be?


Charlie Chong/ Fion Zhang http://www.thesnellgroup.com/Content/infrared-tip-considerations-for-color-palettes.aspx


Certainly, though, Rainbow color palettes can have a powerful impact if used for reports or during presentations. While I personally may find them more challenging for field work, they can be very useful for imaging furnaces, boilers or other high temperature mechanical components when you are using a wider span.

One such example would be inspecting a refractory for thinning that could indicate a potential breach developing. It is also a good palette to use if you are tasked with imaging the distribution of thermal patterns across a surface and need to maximize contrast when evaluating the temperature gradient over a specific area, seen here with this picture of a multi-stage blower (Image Credit: Greg McIntosh, Snell Infrared Canada).

In the end, however, it really does come back to personal preference and a consideration for your particular application. Pick a color palette that you like and is easy to use and interpret. Regardless of which one you select, just remember that it should be intuitive while allowing you to get the best possible focus each and every time you save an image.



5. On Non-uniformity Correction NUCIntroduction: Modern imaging systems are ubiquitous 十分普遍 in a wide range of military and civilian applications including thermal imaging, night vision, surveillance systems, astronomy, fire detection, robotics, and spectral sensing and imaging. At the heart of most modern imaging systems is the focal-plane array (FPA), which consists of a mosaic of detectors positioned at the focal plane of an imaging lens.

An FPA is any detector that has more than one row of detectors. For example, the smallest conceivable FPA detector would have a configuration of 2×2 detectors (two rows and two columns). This configuration is described by the term array. The focal plane of an optical system is a point at which the image is focused. Thus, in an FPA system, an array of detectors is located at a point where the image is focused. Typical infrared FPA systems have an array of 256×256 detectors or more. FPA detectors have high-resolution IR imaging capabilities. An array of detectors staring at the scene rather than a single detector being scanned across the scene means IR cameras can be much smaller, lighter, and more power efficient than a camera with more-elaborate scanning components. Modern infrared FPA systems have the portability of video camcorders and the imaging quality of black-and-white TV cameras.

http://nuc.die.udec.cl/?page_id=18


Non-uniformity and Non-uniformity CorrectionHowever, it is well known that the performance of FPAs is known to be strongly affected by the spatial non-uniformity in the photoresponse of the detectors in the array, also known as fixed-pattern noise, which becomes particularly severe in mid- to far-IR imaging systems.

Individual elements in the FPA differ in responsivity to incoming irradiance, which is the main reason why fixed pattern noise occur in an image. Some pixels end up too bright, some too dark, depending on a multitude of parameters. Some of these parameters may be identified in advance and compensated for, but it is impossible to compensate for all. The result is an image with a superimposed pattern that varies with unknown environmental parameters, leading to a time varying fixed pattern noise. Figure 1 shows two outputs of an 128×128 FPA imaged with two different uniform inputs. The image of the left corresponds to a black-body radiator source at 20°C, and the right image is a black-body (or flat-field) radiator at 24°C. The images clearly show the degradating effect of the spatial nonuniformity.



Figure 1. Examples of three black-body radiators imaged with an FPA. Despite the input irradiance is uniform at 20°C (left) and 24°C (right) the image collected is spatially nonuniform.

20°C 24°C



Despite the advances in detector technology in recent years, detector nonuniformity continues to be a serious challenge, degrading spatial resolution, radiometric accuracy, and temperature resolvability. Moreover, what makes the nonuniformity problem more challenging is the fact that spatial nonuniformity drifts slowly in time; thus a one-time factory calibration will not provide a permanent remedy to the problem.

Nonuniformity correction (NUC) techniques are categorized into two classes, namely, (1) calibration-based and (2) scene-based techniques. In the commonly used two-point calibration technique for example, the normal operation of the FPA is halted as the camera images a uniform calibration target (typically, a blackbody radiation source) at two distinct and known temperatures. The gain and the bias of each detector are then calibrated across the array so that all detectors produce a radiometrically accurate and uniform readout at the two reference temperatures.

Scene-based correction algorithms, on the other hand, do provide significant cosmetic NUC without the need to halt the camera’s normal operation; however, this convenience comes at the expense of compromising radiometric accuracy. Scene-based techniques typically use an image sequence and rely on motion (or changes in the actual scene) to provide diversity in the scene temperature per detector. This temperature diversity, in turn, provides a ‘‘statistical’’ reference point, common to all detectors, according to which the individual detector’s responses can be normalized.



Our ResearchThe NUC-RG has been working on two avenues:■ Real-time nonuniformity correction: the algorithms developed focus on calibrate raw IR data in a frame by frame basis, so NUC can be performed on-line and real-time. Our algorithms include the Constant Range Method, a Kalman filter approach, and a neural network estimator.

■ Block-time nonuniformity correction: this kind of algorithms buffer a block of “l” frames, and then, the estimation of the gain and the bias is performed to finaly compensate the nonuniformity in the whole block of frames. Therefore, the NUC can be performed just on-line. A Kalman filter, its Inverse Covariance form, and the multiple model adaptive estimator are block-time nonuniformity correction algorithms.



Figure 2. A raw IR image sequence collected with an 3-5 [um], InSb FPA cooled camera, Amber model AE-4128. The sequence was taken at 30 [fps], the frame size is 128×128 pixels, each pixel quantized in 16 bits.



Figure 3. The corresponding frames of Figure 2. The nonuniformity was corrected using the Constant Range Method, a real-time nonuniformity correction algorithm.



IR FPA

http://appel.nasa.gov/2012/08/01/kepler-the-long-road-to-other-worlds/


IR FPA - Kepler’s focal plane consists of an array of forty-two charge-coupled devices (CCDs). Each CCD is 2.8 cm by 3.0 cm with 1,024 by 1,100 pixels. The entire focal plane contains 95 mega-pixels.



IR FPA



End Of Reading On Thermographic Camera


Level II Q&A


Q1. Infrared cameras measure:a. the temperature of a surfaceb. the radiosity of a surfacec. the radiosity that is absorbed by the detector in an infrared camerad. the emittance of a surface

Q2. A camera has an IFOV of 1.9 mRad. What is its theoretical minimum spot size at a distance of l00 cm?a. 1.9 cmb. 0.19 cmc. 0.019 cmd. 52 cm

D= σ∙dWhere: D= IFOVgeo, σ = θ subtended in radian, d= detector to object distance.


Q3. The slit response function SRF is used to measure:a. field of view (FOV)b. IFOV measurementc. NETDd. MRTD

Q4. What is the most important factor when inspecting electrical equipment using IR?a. thermal sensitivity of the IR camerab. safetyc. image focusd. thermal span and level


Q5. The plant's main switchgear is to be inspected. The main switchgear has new aluminum busbar. The emissivity of new aluminurn busbar is approximately:a. 1.0b. 0.90c. 0.50d. 0.10

Q6. What weather conditions are necessary for conducting a thermal infrared roof inspection?a. it should have rained within 24 h, inspect during a sunny dayb. it must not have rained within the last 24 h, inspect during a sunny dayc. it must have rained within the last 24 h, inspect at nightd. it must not have rained within the last 24 h, inspect after sundown following a clear sunny day


7. How should the level and span be set when inspecting overhead electrical bus plugs?a. set the camera to auto adjust mode allowing the camera to adjust leveland spanb. set the span wide for the full scene and adjust level to the ambienttemperaturec. set span wide and allow the camera to automatically adjust leveld. set the span very narrow and adjust the level to the temperature of the bus


8. A thermal infrared inspection of a building is conducted to determine the presence of insulation. What is the recommended minimum temperature difference between inside and outside? a. 3 ºC (5 °F)b. 5 ºC (9 ºF)c. 10 ºC (18 °F)d. 20 ºC (36 ºF)

9. An object that is not at thermal equilibrium with its surrounding environment is said to be:a. at steady stateb. thermally isolatedc. thermally transmissived. thermally transient


10. If the amount of insulation in an attic 阁楼 is increased from 10 cm to 20 cm (3.94 in. to 7.87 in.) what effect does it have on the conductive heat transfer?a. heat transfer will stay the sameb. heat transfer will increase by 1/2c. heat transfer will be reduced by 1/2d. heat transfer will increase by 2 times

11. If the temperature difference from inside a house to outside the house decreases from 36 to 9 ºC (64.8 to 16.2 ºF), what effect does it have on the conductive heat transfer through the walls?a. heat transfer will stay the sameb. heat transfer will increase by four timesc. heat transfer will be reduced by four timesd. heat transfer will be reduced by two times


Heat Conduction

q = KA(ΔT)/L

q1 = KA(36)/L

q2 = KA(9)/L

q1/q2= 36/9 = 4?


Q12. When a thermal imaging radiometer is out of calibration and reading temperatures incorrectly, what can be done to bring it back into radiometric calibration? a. perform an external non-uniformity correction (NUC)b. adjust the calibration with a calibrated blackbody reference sourcec. send the camera back to the manufacturer (or relevant body) forrecalibrationd. adjust the emissivity until the camera reads the correct temperature

Q13. The effects of the sun can prevent the accurate inspection of light frame buildings. In accordance with ASTM C 1060, how long should a wall of light frame construction be free from direct solar radiation in order to conduct an infrared inspection of the wall? a. 1hb. 3hc. 5hd. 12 h


14. A kilogram of each of the following materials is heated to 90 ºC (194 ºF). Which of the following materials has the most stored thermal energy?a. airb. aluminumc. steeld. water


ReadingASTM C1060 - 11a Standard Practice for Thermographic Inspection of Insulation Installations in Envelope Cavities of Frame Buildings


Designation: C 1060 – 90 Standard Practice for Thermographic Inspection of Insulation Installations in Envelope Cavities of Frame Buildings1. Scope1.1 This practice is a guide to the proper use of infrared imaging systems for conducting qualitative (≠ quantitative – radiometric) thermal inspections of building walls, ceilings, roofs, and floors, framed in wood or metal, that may contain insulation in the spaces between framing members. This procedure allows the detection of cavities where insulation may be inadequate or missing and allows identification of areas with apparently adequate insulation.

1.2 This practice offers reliable means for detecting suspected missing insulation. It also offers the possibility of detecting partial-thickness insulation, improperly installed insulation, or insulation damaged in service. Proof of missing insulation or a malfunctioning envelope requires independent validation. Validation techniques, such as visual inspection or in-situ R-value measurement, are beyond the scope of this practice.


1.3 This practice is limited to frame construction even though thermography can be used on all building types.2,3

1.4 Instrumentation and calibration required under a variety of environmental conditions are described. Instrumentation requirements and measurement procedures are considered for inspections from both inside and outside the structure. Each vantage point offers visual access to areas hidden from the other side.

1.5 The values stated in SI units are to be regarded as standard. The inch-pound units given in parentheses are for information only.

1.6 This standard does not purport 自称 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. In particular, caution should be taken in the handling of any cryogenic liquids or pressurized gases required for use in this practice. Specific precautionary statements are given in Note 1 and Note 3.


2. Referenced Documents2.1 ASTM Standards:C 168 Terminology Relating to Thermal Insulation E 1213 Test Method for Minimum Resolvable Temperature Difference MRTD for Thermal Imaging Systems


3. Terminology3.1 Definitions—Definitions pertaining to insulation are defined in Terminology C 168.

3.2 Definitions of Terms Specific to This Standard:

3.2.1 anomalous thermal image—an observed thermal pattern of a structure that is not in accordance with the expected thermal pattern.

3.2.2 envelope—the construction, taken as a whole or in part, that separates the indoors of a building from the outdoors.

3.2.3 field-of-view (FOV)—the total angular dimensions, expressed in degrees or radians, within which objects can be imaged, displayed, and recorded by a stationary imaging device.

3.2.4 framing spacing—distance between the centerlines of joists, studs, or rafters.


3.2.5 infrared imaging system—an instrument that converts the spatial variations in infrared radiance from a surface into a two-dimensional image of that surface, in which variations in radiance are displayed as a range of colors or tones.

3.2.6 infrared thermography—the process of generating thermal images that represent temperature and emittance variations over the surfaces of objects.

3.2.7 instantaneous field of view (IFOV)—the smallest angle, in milliradians, that can be instantaneously resolved by a particular infrared imaging system.

3.2.8 masonry veneer—frame construction with a non-load bearing exterior masonry surface.


3.2.9 minimum resolvable temperature difference (MRTD)—a measure of the ability of the operators of an infrared imaging system to discern temperature differences with that system. The MRTD is the minimum temperature difference between a four-slot test pattern of defined shape and size and its blackbody background at which an average observer can discriminate the pattern with that infrared imaging system at a defined distance.

3.2.10 thermal pattern—a representation of colors or tones that indicate surface temperature and emittance variation.

3.2.11 thermogram—a recorded image that maps the apparent temperature pattern of an object or scene into a corresponding contrast or color pattern.

3.2.12 zone—a volume of building served by a single ventilation system. For buildings with natural ventilation only, the whole building shall be considered a zone with all interior doors open.


3.2.12 zone— a volume of building served by a single ventilation system. For buildings with natural ventilation only, the whole building shall be considered a zone with all interior doors open.


4. Summary of Practice4.1 This practice is a guide to the proper use of infrared imaging systems for conducting qualitative thermal inspections of building walls, ceilings, roofs, and floors, framed in wood or metal, that may contain insulation in the spaces between framing members. Imaging system performance is defined in terms of instantaneous field of view (IFOV) and minimum resolvable temperature difference (MRTD). Conditions under which information is to be collected and compiled in a report are specified. Adherence to this standard practice requires a final report of the investigation. This practice defines the contents of the report.

Note: NETD – Noise equivalent temperature difference ( not addressed?)(a measures of the detector’s temperature resolution/sensitivity only without considering equipment, prevailing conditions and operator factors)


NETD - Noise Equivalent Temperature DifferenceNoise Equivalent Temperature Difference is used to measure the performance of a infrared cameras ability discern the minimum level of thermal sensitivity and is very similar to the MRTD with the exception that the test is based on the output of the detector only, without taking into consideration the performance of the infrared cameras image as it would be displayed to a thermographer. The results are usually expressed as the NETD. A common specification for an IR cameras NETD is 0.02 ºC at 30 ºC.

More reading: http://spie.org/x91246.xml

http://www.prothermographer.com/training/IRBasics/qualitative_thermography/netd_noise_equivalent_temperature_difference.htm


5. Significance and Use5.1 Although infrared imaging systems have the potential to determine many factors concerning the thermal performance of a wall, roof, floor, or ceiling, the emphasis in this practice is on determining whether insulation is missing or whether an insulation installation is malfunctioning. Anomalous thermal images from other apparent causes may also be recorded as supplemental information, even though their interpretation may require procedures and techniques not presented in this practice.


6. Instrumentation Requirements6.1 Environmental Factors—The environment has a significant impact on the heat flow through the envelope. As a result, the requirements on thermal imaging instrumentation vary with the interior to exterior air temperature gradient for both interior and exterior inspections and also vary with wind speed for exterior inspections.

6.2 Infrared Imaging System Performance — The ability of an observer to detect thermal anomalies depends on the imager’s powers of thermal and spatial resolution. The practical test for these qualities is whether the operator can distinguish the framing from the envelope cavities under the prevailing thermal conditions with the infrared imaging system at a distance that permits recognition of thermal anomalies. For planning an equipment purchase or a site visit, the following qualities may be considered: ■ The minimum resolvable temperature difference (MRTD) defines temperature resolution. ■ Instantaneous field of view (IFOV) is an indicator of spatial resolution.

Appendix X1 explains how to calculate IFOV and how to measure MRTD.


6.2.1 Spectral Range—The infrared thermal imaging system shall operate within a spectral range between 2 and 14 μm.

6.2.2 Field of View (FOV)—The critical minimum dimensions for discriminating missing insulation in frame construction is two framing spacings wide and one framing spacing high. Outdoors, it is typically convenient to view at least one floor-to-ceiling height across and one-half that distance high. The FOV of the chosen imaging system should encompass these minimum dimensions from the chosen indoor viewing distance, di, and outdoor viewing distance, do. For planning purposes, the angular value of FOV may be calculated for either d (m) by the following equations:

FOVvertical ≥ tan-1 (h/2d) (1)FOVhorizontal ≥ tan-1 (w/2d) (2)

where:h = vertical distance viewed, m, andw = horizontal distance viewed, m.




w½ h

½ θ vertical d

tan (θ/2) = ½ h/d = h/2dθ/2 = tan-1(h/2d)FOVvertical = θ = 2∙tan-1(h/2d) ?

½ h

D or h = σ∙d where σ = FOV ?


7. Knowledge Requirement7.1 This practice requires operation of the imaging system and interpretation of the data obtained. The same person may perform both functions. The operator of the infrared imaging system shall have thorough knowledge of its use through training, the manufacturer’s manuals, or both. The interpretor of the thermographic data shall be knowledgeable about heat transfer through building envelopes and about thermography, including the effects of stored heat, wind, and surface moisture.

7.2 The instrument shall be operated in accordance with the published instructions of the manufacturer.


8. Preferred Conditions8.1 The criterion for satisfactory thermal conditions is the ability to distinguish framing members from cavities. Appendix X2 gives some guidelines for determining whether the weather conditions are likely to be suitable.


9. Procedure9.1 Preliminary Inspection - A preliminary thermographic inspection may be performed to determine whether a thorough inspection, and report, is warranted.

9.2 Background Information - Prepare for the report by collecting information on the building. In order to evaluate the structure, collect the following preliminary data where practical and necessary:

9.2.1 Note each type of building cross section, using visual inspection, construction drawings, or both, to determine what thermal patterns to expect.

9.2.2 Additions or modifications to the structure.

9.2.3 Thermal problems reported by the building owner/ occupant.


9.2.4 Note differences in surface materials or conditions that may affect emittance, for example, metallic finishes, polished surfaces, stains, or moisture. Such differences in emittance cause thermal patterns that are independent of temperature differences.

9.2.5 Orientation of the building with respect to the points of the compass.

9.2.6 Heat sources, such as light fixtures, mounted in or close to the exterior construction.


9.3 Performing On-Site Equipment Check and Settings:9.3.1 Set the instrument gain or contrast to allow the observer to distinguish a framing member from the envelope area around it. In addition, set the imager’s sensitivity so that any anomalies or areas to which they are referenced are not in saturation (maximum brightness or white) or in suppression (minimum brightness or black) on the display.

9.3.2 Verify proper operation of the recording system, if any.

9.3.3 Make a sketch or photograph of each envelope area with references for locating framing members.


9.4 Performing the Inspection:9.4.1 A complete thermographic inspection of a building may consist of an exterior or interior inspection of the complete envelope, or both. Both types of inspection are recommended because each offers access to areas that may be difficult for the other.

9.4.2 Inspect all surfaces of interest from an angle as close to normal to the surface as possible, but at least at an angle that permits distinguishing framing members. Make inspections from several angles, perpendicular, if possible, and at two opposite oblique angles in order to detect the presence of reflected radiation. (1+2 viewing angles)

9.4.3 Make scans from a position that allows a field of view that encompasses at least two framing spacings wide and one framing spacing high for an interior inspection and a floor- oceiling height wide and one-half that distance high for an exterior inspection. (?)


9.4.4 Effective corrective action requires a precise definition of the areas with apparent defects. Record each anomaly with annotation regarding the location of all recognizable building characteristics such as windows, doors, and vents. The record ay accommodate any requirement for calculations of envelope areas with anomalies.


Building IR Thermogram


Capturing Aerial IR Thermogram


Aerial IR Thermogram

http://thermalmapir.com/IRthermalmap.htm


Targeting Aerial IR Thermogram


Capturing Aerial IR Thermogram


10. Thermographic Interpretation10.1 If apparent defects in insulation are not confirmed, corrected, and reinspected at the time of the thermographic survey, then thermograms or other precise identification of the locations and types of apparent defects are required. The interpretation of the thermogram allows determination of the following information:

10.1.1 Locations of the regions where insulation is apparently missing or defective and their total area.

10.1.2 Locations of the regions where the insulation is apparently intact and their total area.

10.1.3 Location and total area of added insulation (if 10.1.1 and 10.1.2 were performed in a thermographic inspection prior to adding insulation).

10.1.4 Estimated total area of surfaces that cannot be inspected.


10.2 Interpretation of thermographic images requires awareness of the following types of patterns:

10.2.1 Intact Insulation—As seen from the warm side of the construction: dark parallel lines, representing the framing; uniformly lighter areas between the framing lines, representing the insulation. As seen from the cool side of the construction: the framing lines are light. The areas containing insulation are uniformly dark.

NOTE 1—Metal framing with no insulation may fit this description. See Note 2.

NOTE 2—Metal framing conducts heat better than both air and insulation. If insulation is present, the thermal contrast between metal framing and the spaces between may be very strong. Independent verification may be needed for metal-framed buildings to establish typical patterns for insulated and uninsulated areas.


10.2.2 Insulation Missing Completely—As seen from the warm side of the construction: light parallel lines, representing the framing; darker areas between the framing lines, representing the empty space between framing members. Convection may be visible in vertical framing, as evidenced by a gradient from dark (cooler) at the bottom of the space to light (warmer) at the top. As seen from the cool side of the construction: the framing lines are dark, the areas between framing are light and convection is still lighter at the top of vertical spaces.

NOTE 3—Metal framing with no insulation may not fit this description. See Note 2.

10.2.3 Insulation Partially Missing—The dominant effect is as described in 10.2.1, except that missing insulation shows as a well-defined dark region, as seen from the warm side and as a light region as seen from the cool side.


10.2.4 Other Thermal Patterns—Irregular variation of the thermal pattern in the spaces between framing members may indicate a combination of possible causes, including varying density of insulation, convection or air leakage, moisture, or thermal bridges. A partial list of examples follows:

10.2.4.1 Variable density insulation often allows air leakage and convection and thereby creates intruding areas of surface temperature variation.

10.2.4.2 Areas where insulation contains significant moisture conduct heat much more readily than dry insulation or no insulation. Within the moist region there may be a mottled and diffused thermal pattern. Temperature variations within the pattern are not extreme.

10.2.4.3 Thermal bridges may be caused by the presence of fasteners or framing members.


10.2.4.4 Air leakage, usually at joints and junctions in the building envelope, typically produces irregular shapes with uneven boundaries and large temperature variations. Air leakage can be detected thermographically when air of a different temperature than the surface viewed comes from the side of the envelope opposite the observer.

10.2.4.5 Indoor temperatures may vary from room to room. This can result in large areas showing brighter than others, as seen during an exterior survey. Independent verification of indoor temperatures can determine whether such variations are due to variations in indoor temperatures or to differences in the thermal qualities of the envelope.

10.2.4.6 If an object has been removed from a surface, there may be a thermal signature where the object insulated the surface. This effect diminishes with time after removal of the object.


10.3 If possible, the cause of the anomalous thermal image shall be determined. This may be done by calculations, ancillary measurements, experience, or by comparing the actual thermogram with reference thermograms for structures with known anomalies. The report should substantiate such determinations.


11. ReportNOTE 4—Much of the report may be recorded on a standard form devised by the user of this practice.

11.1 The report on a thermographic survey shall contain, at a minimum, the following information:

11.1.1 Brief description of the essential construction features of the building. (This information can be based on drawings or other construction documents when available).

11.1.2 Note any unusual surface conditions, such as moisture or reflective materials, and note the means used to account for these conditions.


11.1.3 Geographic orientation of the building with respect to the points of the compass, and a description of the surrounding buildings, vegetation, landscape, and microclimate. This may be done with photographs of each side of the building.

11.1.4 The equipment used, including model and serial number, and any critical settings used during the inspection.

11.1.5 Date and hour of the inspection.

NOTE 5—This practice does not rely on detailed weather information. The ability to distinguish framing members is the critical criterion. Weather records from a nearby weather station should provide sufficient data, when desired.


11.1.6 Sketches/photographs of the building showing the positions of the thermograms. If no thermograms were made, then the following may be substituted:

11.1.6.1 Scale or dimensioned drawings that locate areas with apparently missing insulation, defective installations of insulation, or other anomalies.

11.1.6.2 Markings on the building envelope, for example with tape, that delineate the apparently defective areas.

11.1.7 Thermograms (if obtained) from the inspection with identifications of the region represented and with any interpretations of the thermal images.

11.1.8 Identification of the examined parts of the building envelope and of those not examined.


11.1.9 Results of any analysis dealing with the type and extent of each apparent defect that may warrant remedial action. This may be a simple reference to outlined areas on the thermograms.

11.1.10 Results of any supplementary measurements and investigations.

11.1.11 Optional— stimate of the total area and location where no insulation is apparent.

11.1.12 Optional—Estimate of the total area and location where full insulation is apparent.

11.1.13 Names of members of inspection team and team leader.


12. Precision and Bias12.1 This practice is qualitative in nature. Therefore, the data determined is subject to interpretation. It requires the user to be able to distinguish framing members before proceeding. The appendixes detail the equipment specifications and weather conditions that are likely to meet the criterion of distinguishing framing members. Users can expect to obtain anomalous thermal images from phenomena that are about the size of a framing member or larger. Section 1.2 describes what types of suspected problems the user can expect to detect.

13. Keywords 13.1 building envelope; infrared; in-situ; thermal insulation; wall systems; workmanship


Building Framing


APPENDIXES(Nonmandatory Information)


X1. How To Determine Spatial And Thermal Resolution Of An Infrared Thermal Imaging System X1.1 The user can determine in advance whether an imaging system has an adequate IFOV and MRTD for the conditions of use. First the user must establish typical distances for indoor and outdoor inspections that are compatible with the imaging system (see X1.1.1); secondly, an IFOV calculation may be performed (see X1.1.2); then, MRTD experiments must be performed for those distances (see X1.1.3).

X1.1.1 Criterion Distances—The user may choose convenient distances to be probable maximums for indoor and outdoor scanning. Indoors the distance, di, might be 3 m (about 10 ft). Outdoors, do, might be 5 m (about 16 ft). These distances shall conform to the FOV (see section 6.2.3), IFOV (see X1.1.2), and MRTD (see X1.1.3) of the equipment chosen.


X1.1.2 Instantaneous Field of View (IFOV)—To ensure adequate spatial resolution, the instrument must discriminate a width, s, of one piece of framing from the distance, d, chosen in X1.1.1. The same width, s, pertains to determining MRTD in 6.2.5.

The instrument should have an IFOV defined by the following equation:

In the USA a typical value of s would be 0.0381 m (1.5 in.), when viewed from d = 5 m (about 16 ft) would require an IFOV of less than 3.8 milliradians.

s = IFOV x d ?s = 3.8 x 10-3 x 5 = 0.019m ?s = 2(IFOV x d) ?s’ = 2(3.8 x 10-3 x 5) = 0.038m ?




w½ h

½ θ vertical d

tan (θ/2) = ½ h/d = h/2dθ/2 = tan-1(h/2d)FOVvertical = θ = 2∙tan-1(h/2d) ?

½ h

D or h = σ∙d where σ = FOV ?


X1.1.3 Minimum Resolvable Temperature Difference (MRTD)—Depending on the construction subject to inspection and the thermal conditions, the instrument shall have an MRTD, as defined by the following equation at the distance, d, chosen in X1.1.1:

where:| = the absolute value symbol,R = thermal resistance, m2K/W (or ft2h°F/Btu),h = the surface film coefficient, W/m2K (or Btu/°Fh ft2),1 = properly insulated area,2 = defectively insulated area,ΔT = difference between inside and outside ambient temperatures, K (or °F), Δ R = R1 − R2.


Tables X1.1-X1.3 list the MRTD required for the imaging system assuming that the imager is located inside the building being tested and the building’s interior temperature is at 25 6±5°C (77±9°F). The MRTD requirement for the imaging system can also be estimated, using Eq X1.2. For exterior surveys the film coefficient, h, changes with wind speed.

X1.1.4 Test for MRTD— MRTD of the thermal imaging system is defined by the following test conditions:

X1.1.4.1 Instrument Setting—The thermal imaging system shall be set at the sensitivity that detects the smallest temperature variations.


X1.1.4.2 Criterion Distance—MRTD shall be determined for indoors and outdoor applications at the distances di and do chosen in X1.1.1.

X1.1.4.3 Test Target Pattern—The test target shall consist of two plates with controlled, known temperatures, located at the criterion distance, d, in front of the imaging system. The near plate shall have a four-bar test pattern of w = (s/2)/cycle and a 7:1 aspect ratio. The dimension, s, is the same value as in X1.1.2, defined as the width of a single piece of framing. Other size patterns of the same aspect ratio may be used as long as w/d remains constant. See Fig. X1.1 for an illustration of the MRTD experimental set-up.


X1.1.4.4 MRTD Test Procedure—Someone slowly increases the temperature difference between the two plates of the target without communicating with the observer of the display on the imaging system. The observer announces when the test pattern comes into view. The difference in temperature at this point is the MRTD for that test condition.

X1.1.4.5 Test Replicates—A minimum of three separate observers shall perform the procedure in 6.2.6.4 to establish an average value for MRTD.


TABLE X1.1 Required MRTD for R-0.352 (R-2) to R-1.76 (R-10)Difference at 25 ± 5°C Ambient Temperature


FIG. X1.1 Test for Minimum Resolvable Temperature Difference (MRTD) of Infrared Imaging System NOTE— A test pattern, consisting of four rectangular slots, permits a comparison of the temperature of the near plate of the test target with the far plate. The plates are initially at the same temperature. Someone increases the temperature difference between plates until an observer announces when the test pattern comes into view on the display. The difference in temperature at this point is the MRTD for that test condition.


FIG. X1.1 Test for Minimum Resolvable Temperature Difference (MRTD) of Infrared Imaging System


X2. Preferred Conditions For Performing Infrared Inspections Of Frame ConstructionX2.1 Infrared inspection requires a sufficient difference in temperature from inside to outside (ΔT) for a sufficiently long period of time, as described in this section, to produce discernible differences between areas with studs and areas that may contain insulation. The preferred measurement of ΔT is surface to surface, because this minimizes problems with accounting for solar and wind effects. Air-to-air measurements are also permitted under this practice. The following environmental conditions are suggested for thermographic inspections:

X2.2 Minimum ΔT—Minimum temperature difference (ΔT) of 10°C (18°F) between interior and exterior surface or ambient air temperatures for a period of 4 h prior to test.


X2.3 Using Ambient Air Temperature Measurements— Ambient air temperature measurements cannot account for the strong radiative effects of the sun or for convective effects from wind, so the following precautions should be taken when using air temperature measurements for ΔT:

X2.3.1 Avoid Solar Radiation— No direct solar radiation on the inspected surfaces for approximately 3 h previous to the inspection for light frame construction and approximately 8 h for masonry veneer construction. ΔTs greater than 10°C reduce these times. Direct sunlight and other strong sources of thermal radiation make discrimination of uninsulated areas unreliable. Exterior surveys should be performed after sunset and before sunrise for best results.

X2.3.2 Avoid Wind— For exterior surveys, the wind speed should be less than 6.7 m/s (15 mph) and the building surface should be dry.


X2.4 Other Conditions—Although it is recommended that the conditions in X2.3-X2.3.2 prevail at the time of inspection, it is recognized that the thermographic inspections can be performed under other conditions if sufficient knowledge is used in taking and interpreting the thermograms. For example, a wall exposed to direct solar radiation will experience a temperature reversal; the studs and voids will appear warm and the insulated section cold on interior inspections. Interior surveys may be possible on veneer surfaces or ceilings under attics an hour or two after sunrise.


Minimum ΔT—Minimum temperature difference (ΔT) of 10°C (18°F) between interior and exterior surface or ambient air temperatures for a period of 4 h prior to test.

No direct solar radiation on the inspected surfaces for approximately 3 h previous to the inspection for light frame construction and approximately 8 h for masonry veneer construction.

Exterior surveys should be performed after sunset and before sunrise for best results.

For exterior surveys, the wind speed should be less than 6.7 m/s (15 mph) and the building surface should be dry.


End Of Reading ASTM C1060


Q15 . Latent heat energy can be described as:a. the energy that creates or breaks the molecular bonds of the phase

state of a materialb. the energy that when added to a material will cause its temperature to

increasec. the energy released by a material that will cause its temperature to

decreased. the energy released by an object that will break the molecular bonds of a

material

Q16. Which of the following surfaces will generally provide the most accurate radiometric temperature measurement?

a. thin film plasticb. oxidized aluminumc. glassd. water-based paint


Q17 . The instantaneous field of view (IFOV) measurement of a radiometric system is 1.2 mRad. What is the maximum size object this system can accurately measure at a distance of 25 m?a. 3 mb. 3 mmc. 3 cmd. 20.8 cm

D= IFOV x d = 1.2 x10-3 x 25 = .03 m = 3cm#


Q18. The accuracy of the liquid level gage on the 946,353 L (250,000 gal) oil tank is being questioned. Verification of the liquid level is critical but the safety manager is not available to issue a confined entry permit to physically verify the level. It is spring time. Last night was cool and it is now noon and a bright sunny day. What might you consider to determine the oil level?

a. Assume the liquid level indicator is correct unless definitive proof is submitted otherwise.

b. Examine the tank with your infrared camera. When you see no level indication between liquid and air it is safe to open the tank access door.

c. Examine the tank with your infrared camera. The air should be warmer than the liquid and should provide a clear indication of the liquid level.

d. Examine the tank with your infrared camera. The air will be cooler than the liquid and should provide a clear indication of the liquid level.


19. How hot does an electrical connectioncneed to be for it to be a classified as a serious problem?a. 1 to 5 ºC (33.8 to 41 ºF)b. 5 to 15 ºC (41 to 59 ºF)c. greater than 15 ºC (59 ºF)d. depends on the criticality of equipment to continued safe operation.


Tank Infrared Thermogram


To the naked eye, no emissions from an oil storage tank are visible. But viewed with an infrared lens, escaping methane is evident.

http://wvhighlands.org/wv_voice/?p=2344


Infrared camera shows invisible toxic gas escaping from a tank

http://tomsviewpoint.blogspot.com/2011/04/fracking-accidents-threaten-farms-and.html


Methane IR Transmission Spectrum


Q20. Most imaging infrared radiometers operate in the 3 to 5 or 8 to 12 μm band. This is because of:

a. atmospheric reflection of solar radiation is adequately attenuated in these two bands

b. the electromagnetic energy emitted by a target outside these two bands is generally too small to provide usable data

c. atmospheric absorption within these two bands is small enough to provide minimal impact on radiometry

d. technological limits of producing detectors with uniform characteristics except for these two wave bands.

Q21. Long wave (8-14 μm) infrared thermography is an excellent tool for inspecting all except which of the following:

a. drive belts for proper alignment b. bearings for signs of impending failure c. thin film plastics d. the temperature for creating baseline comparison


22. While doing an IR inspection of a heated stainless steel component with several surface holes you notice that one of the holes appears hotter than the others. What could explain this?

a. that hotter hole is warmer than the other holes b. that hole must be reflectiog something hotter than the other holes c. the hotter hole must have more thermal capacitance d. the hotter hole probably is deeper than the other holes

23. After heating one side of a honeycomb composite with a 4 ply graphite epoxy face sheet, and thermally viewing from the same side, you notice a dark or cool indication that seems to be confined to a group of honeycomb cells. What is the probable cause of this thermal pattern?

a. there is a disband between the top sheet and the honeycomb cells b. there is a disbond between the bottom face sheet and the honeycomb c. there is most likely water or some other liquid in the cells d. the honeycomb is most likely crushed


24. From the ground you see a hot spot on a 1 in. (2.54 cm) bolted connector of a transmission line that is approximately 27.4 m (90ft) away. When you go to measure the temperature, it reads much lower than you think it should be, in fact it appears to be below ambient. What is a probable reason?

a. your IFOV is not turned on b. you are not in focus c. you are too far away to accurately measure d. the emissivity is probably set incorrectly

25. Thin film plastics, such as polyethylene, are thermally different from most materials because they are:

a. highly reflective to short-wave thermal radiation b. highly absorptive to long-wave thermal radiation c. highly transmissive to both mid- and long-wave thermal

radiation d. opaque to both mid- and long-wave thermal radiation


26. Why is infrared thermal imaging often used by building analysts to locate mold growth?

a. wold is exothermic and appears warmer on the surface b. wold is endothermic and absorbs heat from surroundings, thus appearing

warm c. wold grows on damp surfaces, which appear cooler due to

evaporative cooling d. wold is endothermic thus cooling the surface

27. Which of the following materials has the highest thermal capacitance? a. steel b. brickc. waterd. glass


Specific Heats of Various Substances

http://www.usc.edu/org/cosee-west/Jan292011/Heat%20Capacity%20and%20Specific%20Heat.pdf


28; Which of the following factors will have the greatest affect on the accuracy of a temperature measurement of a loose connection on a copper alloy bolted plate connection? Assume the copper has an emissivity of 0.28.

a. estimating the copper has an emissivity of 0.29 b. setting relative humidity at 65% ather than the preset 50% c. leaving the distance to object set to 3.05 m (10ft) instead of 4.6 m (15ft) d. adjusting the background temp 76.6 °C ( 170 °F) to actual

temperature of 28.3 °C (83 °F)

Q29. Which of the following list the correct order of thermal capacitance? from highest to lowest.

a. steel, air, waterb. air, water, woodc. water, steel aird. water, air, steel


30. To measure the temperature of heater tubes in a natural gas-fired furnace using a mid-wave sensing system you must:

a. add the correct filter b. set emissivity at 0.05 c. put a piece of tape on the heater tube d. mid-wave systems are not suitable for furnace inspections

31. You have found a motor bearing that is 32 °F warmer than normal. Convert this temperature difference ( ΔT) to degrees Celsius.

a. 0°C b. 17.7 °C c. 89.6°C d. 100°C


32. Which of the following typically has the greatest influence on taking a radiometric temperature measurement on a low-emissivity object?

a. background temperature b. foreground air temperature c. distance to the target d. relative humidity

33. Which of the following camera settings has the greatest impact on taking an accurate temperature measurement of an object that actually has an emissivity of 0.87, a background temperature of 23.9 °C (75 °F), relative humidity of 50% and distance to the object is 3.05 m (10ft)?

a. relative humidity set at 40% instead of 50% b. distance to object set at 5.5 m (18ft) c. emissivity set at 0.72 d. background temperature set at 21.1 °C (70 °F) instead of 23.9 °C (75 °F)


Electromagnetic Spectrum (IR) & Corresponding Energy


Q34. While conducting a roof moisture inspection at night after a sunny day, why is it important for the roof surface to be dry?

a. evaporating water will mask the thermal patterns below the roof surface

b. a dry roof surface is a better conductor than a wet roof surface c. it is better to have a wet roof surface so you can find the leak easier d. a dry roof surface will radiate better to the cold sky

Q35. Which of the following materials emits quite differently in the mid-wave (3.5-5 microns) band than in the long-wave band (8-14 microns)?

a. plate glass b. polished aluminum c. painted steel d. ceramic


36. Using an infrared system with an IFOVmeasurement ratio of 180:1. What is the smallest size object you can accurately measure at a distance of 3 m (3.3 ft)?

a. 16.6 mm (0.65 in.) b. 18.7 mm (0.74 in.) c. 50.0 mm (1.97 in.) d. 166.0 mm (6.54 in.)

37. You are looking at an electrical connection 20 m in the air. What IFOV measurement is required to accurately measure the temperature on the 2.54 cm (1 in.) head of a bolt?

a. 0.125 mRad b. 1.25 mRad c. 2.5 mRad d. 25 mRad


38. The IR system being used stores images to videotape. Back in the office you find you'd like to adjust the level and span of an image. How is this accomplished?

a. digitize the thermal image and adjust the level and span in software b. import the video into your manufacturer's software and adjust level

and span c. send the video to your camera manufacturer for conversion to 12 bit data d. data captured on videotape will not allow the adjustment of level and

span

39. The easiest and cheapest way to improve the spatial resolution of a thermal image is to:

a. buy a new imager with a detector that has more detector elements b. move the camera as close to the target as possible without

compromising safety c. install a telephoto lens d. defocus the lens


40. Atmospheric attenuation for imaging systems that sense 8-12 microns thermal radiation is:

a. greater than the attenuation for 3-5 micron radiation b. less than the attenuation for 3-5 micron radiation c. equal to the attenuation for 3-5 micron radiation d. greater than the attenuation for 6-8 micron radiation


The Video Tapes


Other Storage Devices


41. When looking at a thermal image, the thermographer is viewing: a. thermal patterns representing temperatures on the surface of the target b. thermal patterns of objects reflected from the surface of the target c. radiance (combined reflected, transmitted and emitted energy)

patterns from the surface of the target d. radiance (combined reflected, transmitted and emitted energy) patterns of

objects reflected from the surface of the object

42. As a surface cools, the peak of its radiated infrared energy: a. shifts to longer wavelengths b. shifts to shorter wavelengths c. remains constant if emissivity remains constant d. remains constant even if emissivity varies


43. The spectral band in which glass transmits infrared radiation most efficiently is the __ __ __ region.

a. 2-4 μm b. 5-7 μm c. 6-10 μm d. 10-15 μm

Q44. When water freezes: a. heat energy is absorbed from the surroundings b. the volume decreases and conductivity increases c. heat energy is released to the surroundings d. the volume increases and conductivity decreases


Q45. The energy content of a gram of steam at 100 ºC (212 ºF) is much higher than that of a gram of water at 100 ºC (212 ºF) because of:

a. a 20 ºC ( 68 ºF) temperature difference b. the latent heat of vaporization c. the additional shortwave thermal radiation d. the latent heat of fusion

Q46. The heat capacity of an object is: a. inversely proportional to the material's specific heat b. directly proportional to a material's specific heat and density c. inversely proportional to its density d. the ratio of short-wave infrared radiation absorbed by an object to long-

wave infrared radiation emitted by the object

Q k∙∝ ρ (more reading to rationalized on density contribution)


Specific Heat The specific heat is the amount of heat per unit mass required to raise the temperature by one degree Celsius. The relationship between heat and temperature change is usually expressed in the form shown below where c is the specific heat. The relationship does not apply if a phase change is encountered, because the heat added or removed during a phase change does not change the temperature.

Q = cmΔTWhere: Q=heat added, c=specific heat, m=mass, T=change in temperature

The specific heat of water is 1 calorie/gram °C = 4.186 joule/gram °C which is higher than any other common substance. As a result, water plays a very important role in temperature regulation. The specific heat per gram for water is much higher than that for a metal, as described in the water-metal example. For most purposes, it is more meaningful to compare the molar specific heats of substances.

The molar specific heats of most solids at room temperature and above are nearly constant, in agreement with the Law of Dulong and Petit. At lower temperatures the specific heats drop as quantum processes become significant. The low temperature behavior is described by the Einstein-Debye model of specific heat.

http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/spht.html


Q47. What component of earth's atmosphere will completely or partially absorb infrared electromagnetic energy in the wave band of 6-8 μm?

a. water vapor (H20) b. nitrogen (N) and oxygen ( 02) combined c. oxygen (02) d. nitrogen (N)

Q48. Since wind will convectively cool building components reducing thermal differences, it is not advisable to perform building inspections on the windward side when air speeds are in excess of:

a. 6 km/h (3.7 mph) b. 12 km/h (7.5 mph) c. 18 km/h (11 mph) d. 24 km/h (15 mph)


Visible Spectrum (0.35 μm ~ 0.75 μm)


Atmosphere IR Transmission Spectrum As the main part of the ‘window’ spectrum, a clear electromagnetic spectral transmission ‘window’ can be seen between 8 and 14 µm. A fragmented part of the ‘window’ spectrum (one might say a louvred 百叶窗 part of the 'window') can also be seen in the visible to mid-wavelength infrared between 0.2 (visible) and 5.5 µm.

https://en.wikipedia.org/wiki/Infrared_window


Atmosphere IR Absorption Spectrum


Methane IR Transmission Spectrum


Atmosphere IR Transmission Spectrum


Atmosphere IR Absorption Spectrum


ReadingHeat Transfer before Cruising into Level III Q&A.

http://www.g9toengineering.com/resources/heattransfer.htm


Heat TransferHeat is energy or more precisely transfer of thermal energy. As energy, heat is measured in watts (W) whilst temperature is measured in degrees Celsius (°C) or Kelvin (K). The words “hot” and “cold” only make sense on a relative basis. Thermal energy travels from hot material to cold material. Hot material heats up cold material, and cold material cools down hot material. It is really that simple. When you feel heat, what you are sensing is a transfer of thermal energy from something that's hot to something that is cold.

The discipline of heat transfer is concerned with only two things: temperature, and the flow of heat. Temperature represents the amount of thermal energy available, whereas heat flow represents the movement of thermal energy from place to place. On a microscopic scale, thermal energy is related to the kinetic energy of molecules. The greater a material’s temperature, the greater the thermal agitation of its constituent molecules (manifested both in linear motion and vibrational modes).



ConductionThe most efficient method of heat transfer is conduction. This mode of heat transfer occurs when there is a temperature gradient across a body. In this case, the energy is transferred from a high temperature region to low temperature region due to random molecular motion (diffusion).

Conduction occurs similarly in liquids and gases. Regions with greater molecular kinetic energy will pass their thermal energy to regions with less molecular energy through direct molecular collisions.

In metals, a significant portion of the transported thermal energy is also carried by conduction-band electrons. Different materials have varying abilities to conduct heat. Materials that conduct heat poorly (wood, styrofoam) are often called insulators. However, materials that conduct heat well (metals, glass, some plastics) have no special name.

The simplest conduction heat transfer can be described as “one-dimensional heat flow” as shown in the following figure. The rate of heat flow from one side of an object to the other, or between objects that touch, depends on the cross-sectional area of flow, the conductivity of the material and the temperature difference between the two surfaces or objects.



q = k∙A δt/ δxwhere q is the heat transfer rate in watts (W), k is the thermal conductivity of the material (W/m.K), A is the cross sectional area of heat path, and δt/ δx is the temperature gradient in the direction of the flow (K/m).

The above equation is known as Fourier’s law of heat conduction. Therefore, the heat transfer rate by conduction through the object in the above figure can be expressed as:

q = k∙A Δt/ L



Where L is the conductor thickness (or length), ΔT is the temperature difference between one side and the other (for example, ΔT = T1 – T2 is the temperature difference between side 1 and side 2).

The quantity (ΔT/L) in Equation (16.5) is called the temperature gradient: it tells how many ºC or K the temperature changes per unit of distance moved along the path of heat flow. The quantity L/kA is called the thermal resistance.

Rcond = d/k∙A or L/k∙A

Thermal resistance has SI units of kelvins per watt (K/W). Notice from Equation (16.6) that the thermal resistance depends on the nature of the material (thermal conductivity k and geometry of the body d/A).

It is clear from the above equation that decreasing the thickness or increasing the cross-sectional area or thermal conductivity of an object will decrease its thermal resistance and increase its heat transfer rate.



Convection A slower method of heat transfer is convection, which involves fluid (both gas & liquid) currents that carry heat from one place to another. In conduction, energy flows through a material but the material itself does not move. In convection, the material itself moves from one place to another. The convection heat transfer is comprised of two mechanisms:

(1) random molecular motion (diffusion) and (2) energy transferred by bulk or macroscopic motion of the fluid. (3) by conduction during momentarily collision?

Heat transfer from a solid to a fluid (liquid or gaseous) is more complex than solid-solid transfer as heat differentials within the fluid generally cause internal movement known as convection currents. As volume increases with temperature, warmer areas of a fluid have less mass than colder areas. Air is poor conductor of heat, but it can easily flow and carry heat by convection. The use of sealed, double-paned windows replaces the larger air gap between a storm window and regular window with a much smaller gap. The smaller air gap minimizes circulating convection currents between the two panes.



The magnitude of convective heat flow within the fluid depends upon the area of contact with the solid, its viscosity, velocity past the solid, flow characteristics and the overall temperature difference between the two. The term convection has also been used historically to describe the transport of heat from one solid to another separated by a fluid medium.



Newton’s law of cooling expresses the overall effect of convection:

q = h∙A∙ΔT

Where h is the convection heat transfer coefficient (W/m2K), A is the surface area, ΔT = Ts – Tf is the temperature difference between the surface temperature Ts, and the fluid temperature Tf . As in the case of conduction, thermal resistance is also associated with the convection heat transfer and can be expressed as

Rconv = 1/h∙A

The convection heat transfer may be classified according to the nature of fluid flow. Forced convection occurs when the flow is caused by external means, such as a fan, a pump, etc.



RadiationThe least efficient method of heat transfer is radiation. Radiant heat is simply heat energy in transit as electromagnetic radiation. All materials radiate thermal energy in amounts determined by their temperature, where the energy is carried by photons of light in the infrared and visible portions of the electromagnetic spectrum. In this case, heat moves through space as an electromagnetic radiation without the assistance of a physical substance. All objects that contain heat emit some level of radiant energy. The amount of radiation is inversely proportional to its wavelength (the shorter the wavelength the greater the energy content) which is, in turn, inversely proportional to its temperature (in °K).The Sun’s heat is an example of thermal radiation that reaches the Earth. Radiative heat is transferred directly into the surface of any solid object it hits (unless it is highly reflective), but passes readily through transparent materials such as air and glass. An ideal thermal radiator or a blackbody, will emit energy at a rate proportional to the forth power of its absolute temperature and its surface area.



Mathematically, that is

qemitt = σ∙A∙T4

where s is a proportionality constant (Stefan-Boltzmann constant = 5.669 x 10-8 W/m2∙K4). The above equation is called the Stefan-Boltzmann law of thermal radiation and it applies only to the blackbodies. The fourth-power temperature dependence implies that the power emitted is very sensitive to temperature changes. (example: If the absolute temperature of a body doubles, the energy emitted increases by a factor of 24 = 16.) For bodies not behaving as a blackbody a factor known as emissivity ε, which relates the radiation of a surface to that of an ideal black surface is introduced. The equation becomes:

qemitt = ε∙σ∙A∙T4



The emissivity ranges from 0 to 1; e = 1 for a perfect radiator and absorber ( a blackbody) and e = 0 for a perfect radiator (? reflector?) . Human skin, for example, no matter what the pigmentation, has an emissivity of about 0.97 in the infrared part of the spectrum. While a polished aluminum has an emissivity of about 0.05.

Thermal radiation from a body is used as a diagnostic tool in medicine. A thermogram shows whether one area is radiating more heat than it should, indicating a higher temperature due to abnormal cellular activity. Thermography or thermovision in medicine is based on the natural thermal radiation of the skin. Most advantage is the radiance free of the measuring principle.

Certain body regions have different temperature levels. If one exposes the body e.g. to a cooling attraction, then the body zones of the skin react, in order to repair the heat balance of the body. Thereby the thermal regulation of diseased body regions and organs is different to healthy one. The so-called "regulation thermography" is based on this principle.



Human skin, for example, no matter what the pigmentation, has an emissivity of about 0.97 in the infrared part of the spectrum. While a polished aluminum has an emissivity of about 0.05.

http://www.cultureadventure.dk/tag/safari/


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End Of Reading Heat Transfer


Q49. Which of the following statements regarding infrared emission and absorption is false?

a. good emitters are good absorbers b. poor absorbers are poor emitters c. good reflectors are good emitters d. poor reflectors are good absorbers

Q50. Radiosity is defined as: a. the perfect emittance of a blackbody surface b. detectivity/transmissivity c. a graybody whose emissivity is less than 1 d. the total radiant exitance leaving a surface (reflectance, emittance

and transmittance)


51. Distribution of energy over the wavelength spectrum for a given temperature is best described by which of the following?

a. Planck's Law b. Stefan-Boltzmann Law c. Newton's Law d. Fourier's Law


ReadingPlanck’s Law



Planck's law (colored curves) accurately described black body radiation and resolved the ultraviolet catastrophe (black curve).


Planck's law describes the electromagnetic radiation emitted by a black body in thermal equilibrium at a definite temperature. The law is named after Max Planck, who originally proposed it in 1900. It is a pioneering result of modern physics and quantum theory.

The spectral radiance of a body, Wa describes the amount of energy it gives off as radiation of different frequencies. It is measured in terms of the power emitted per unit area of the body, per unit solid angle that the radiation is measured over, per unit frequency. Planck showed that the spectral radiance of a body at absolute temperature T is given by

where k the Boltzmann constant, h the Planck constant, and c the speed of light in the medium, whether material or vacuum. The behavior is illustrated in the figure shown above. The Planck Law gives a distribution that peaks at a certain wavelength, the peak shifts to shorter wavelengths for higher temperatures, and the area under the curve grows rapidly with increasing temperature.


The Wien and Stefan-Boltzmann LawsThe behavior of blackbody radiation is described by the Planck Law, but we can derive from the Planck Law two other radiation laws that are very useful. The Wien Displacement Law, and the Stefan-Boltzmann Law are illustrated in the following equations. The Wien Law gives the wavelength of the peak of the radiation distribution, while the Stefan-Boltzmann Law gives the total energy being emitted at all wavelengths by the blackbody (which is the area under the Planck Law curve). Thus, the Wien Law explains the shift of the peak to shorter wavelengths as the temperature increases, while the Stefan-Boltzmann Law explains the growth in the height of the curve as the temperature increases. Notice that this growth is very abrupt, since it varies as the fourth power of the temperature.

Stefan-Boltzmann Law: E =σT4

Wien’s Law: λmax = α/T

http://csep10.phys.utk.edu/astr162/lect/light/radiation.html


Blackbody Radiation "Blackbody radiation" or "cavity radiation" refers to an object or system which absorbs all radiation incident upon it and re-radiates energy which is characteristic of this radiating system only, not dependent upon the type of radiation which is incident upon it. The radiated energy can be considered to be produced by standing wave or resonant modes of the cavity which is radiating.

The amount of radiation emitted in a given frequency range should be proportional to the number of modes in that range. The best of classical physics suggested that all modes had an equal chance of being produced, and that the number of modes went up proportional to the square of the frequency. But the predicted continual increase in radiated energy with frequency (dubbed the "ultraviolet catastrophe") did not happen. Nature knew better.

http://hyperphysics.phy-astr.gsu.edu/hbase/mod6.html#c4


■ωσμ∙Ωπ∆º≠δ≤>ηθφФρ|β≠Ɛ ʋ ∠ λ α ρτ ±

Radiation modes in a hot cavity provide a test of quantum theory

Modes per unit frequency per unit volume

Probability of occupying modes

Average energy per mode

Equal for all modes

Quantized modesrequire hѵ energyto excite uppermodes, less probable

Classical

Quantum



Cavity Modes A mode for an electromagnetic wave in a cavity must satisfy the condition of zero electric field at the wall. If the mode is of shorter wavelength, there are more ways you can fit it into the cavity to meet that condition. Careful analysis by Rayleigh and Jeans showed that the number of modes was proportional to the frequency squared.

#modes ∝ ѵ2 = 8πѵ2/c3



Planck Radiation Formula From the assumption that the electromagnetic modes in a cavity were quantized in energy with the quantum energy equal to Planck's constant times the frequency E= hѵ , Planck derived a radiation formula. The average energy per "mode" or "quantum" is the energy of the quantum times the probability that it will be occupied (the Einstein-Bose distribution function):

E = hѵ/(ehv/kT -1) -1

This average energy times the density of such states, expressed in terms of either frequency or wavelength



gives the energy density, the Planck radiation formula.

The Planck radiation formula is an example of the distribution of energy according to Bose-Einstein statistics. The above expressions are obtained by multiplying the density of states in terms of frequency or wavelength times the photon energy times the Bose-Einstein distribution function with normalization constant A=1.

To find the radiated power per unit area from a surface at this temperature, multiply the energy density by c/4. The density above is for thermal equilibrium, so setting inward=outward gives a factor of 1/2 for the radiated power outward. Then one must average over all angles, which gives another factor of 1/2 for the angular dependence which is the square of the cosine.

Energy per unit volume per unit wavelength

Energy per unit volume per unit frequency

Sѵ



Rayleigh-Jeans vs Planck Comparison of the classical Rayleigh-Jeans Law and the quantum Planck radiation formula. Experiment confirms the Planck relationship.


Blackbody Intensity as a Function of Frequency


Applications of the Planck Radiation Formula


Comments: P, The total power per unit area from a blackbody radiator can be obtained

by integrating the Planck radiation formula over all wavelengths. The radiated power per unit area as a function of wavelength.

λmax, When the temperature of a blackbody radiator increases, the overall radiated energy increases and the peak of the radiation curve moves to shorter wavelengths. When the maximum is evaluated from the Planck radiation formula, the product of the peak wavelength and the temperature is found to be a constant.


Pyrometer (fire measuring) devices read temperatures by measuring theintensity of IR radiation emitted from an object. All objects above absolutezero temperature (0°K) radiate and absorb thermal energy.

Narrow-band pyrometers typically operate in accordance with Planck’s law and

broad-band pyrometers operate in accordance with the Stefan-Boltzmann law.

Noncontacting pyrometers have a broad price range with models incorporating blackbody correction commanding the highest prices.


End Of Reading Planck Law


On further reading, what is your choice of correct answer?51. Distribution of energy over the wavelength spectrum for a given

temperature is best described by which of the following? a. Planck's Law b. Stefan-Boltzmann Law c. Newton's Law d. Fourier's Law

Keywords:• Distribution of energy over the wavelength spectrum for a given

temperature

Comments:• Stephen-Boltzmann Law integrate area under the curve to derive the total

power per unit area. • Planck Law explained on the distribution of energy over the frequency (at

each particular differential wavelength).


Stephen-Boltzmann LawIs the wavelength independent rate of emission of radiant energy per unit area, given by;

W = ε B T4

Planck LawIs the radiation intensity of the emittance at each particular differential wavelength, given by;

W(λ) = 2πhc2/(λ5)∙(e hc/λkT – 1)-1

W(λ) = The rate of emission, radiant energy per unit energy as a function of wavelengthλ = The wavelength of the emitted radiationh = Planck constant 6.625 x 10-34 J∙sc = Speed of light 2.998 x 108 m∙s-1

k = Boltzmann constant 1.380 x 10-23 J∙K-1


Wien LawWavelength of maximum emittance is given by the single temperature evaluation;

λmax =b/T

b = Wien displacement constant 2879 μm∙K-1


Level III Q&A


1. Energy is measured in units called:a. kelvinb. joulec. wattd. Rankine

2. You are asked to inspect a new paper laminating process, with a long oven and stainless steel rollers, 91.44 cm (36 in.) wide. The paper is laminated with a foil, and only the foil side is visible as it curves around the stainless steel roller at the oven exit. It is important to ensure the foil temperature is uniform at the oven exit for the adhesive to cure properly. What is the best way to ensure the material is cured?

a. view the nip between the roller and the foil with an infrared radiometric imager

b. use a thermocouple to measure the moving foil temperature. c. use reflective radiometry to get an accurate temperature of the foil d. increase the emissivity of the foil with black paint


3. When observing an object at 51.85 °C (325 K), which of the following detectors has the greatest detectivity (D*)?

a. HgCdTe (8 to 12 μm) cooled to -19.6.15 °C (77 K) b. triglyqene sulfate (8 to 12 μm) at ambient c. InSb (3 to 5 μm) cooled to -196.15 °C (77 K) d. PtSi (3 to 5 μm) cooled to -196.15°C (77 K)

λmax = 2897/325 = 8.91μm

Charlie Chong/ Fion Zhang http://www.infraredtraininginstitute.com/black-body-radiation/

Wien’s Law

λmax = 2897/325 = 8.91μm


Wien’s Law

Wien's LawExample at T-325Kλmax = 2897/325 = 8.91μm


Wie

n's

Law


Wien’s Law


4. Which device would be most appropriate for measuring the surface temperature of polyethylene film?

a. a focal plane array radiometer with a InSb detector (3 to 5 μm) cooled to 77 K (-196.15 °C)

b. a single element scanner with HgCdTe detector (8 to 12 μm) cooled to 77 K (-196.15 °C)

c. infrared point radiometer filtered to detect 3.45 μm radiation d. calibrated hi- metal thermometer


Polyethylene Transmission Spectrum

λ ≈ 1/2900 cmλ ≈ 3.44μm


Wave NumberThe term wave number refers to the number of complete wave cycles of an electromagnetic field (EM field) that exist in one meter (1 m) of linear space. Wave number is expressed in reciprocal meters (m-1).

The wave number for an EM field is equal to 2 pi divided by the wavelength in meters. (In some references, it is defined as the reciprocal of the wavelength in meters; in still others, it is defined as the reciprocal of the wavelength in centimeters.) As the wavelength grows shorter, the wave number becomes larger.

One of the definition:it is defined as the reciprocal of the wavelength in centimeters.

Example: what is the wave number for λ=3μm3μm = 3 x 10-6 m = 3 x 10-4 cmWave number = 1/(3x10-4cm) = 3333 cm-1

http://whatis.techtarget.com/definition/wave-number


5. Liquid-in-glass thermometers are designed and calibrated for three conditions of use. Which of the following is not a condition of use for a liquid- n-glass thermometer.a. suspended immersionb. total immersionc. partial immersiond. complete immersion

6. Which of the following nonuniformity corrections (NUC) will best provide both uniform detector response and correct for offset between the target signal and the detector response over the temperature range of an active pulse IR inspection?a. one point externalb. one point internalc. two point externald. two point internalhttp://www.ndt.net/article/qirt2010/papers/qirt2010-101.pdf


7. The energy emitted from a piece of metal is measured and the temperature is determined to be 900 °C (1652 °F) assuming a surface emissivity of 0.79. It is later found that the true emissivity is 0.84. What is the closest temperature of the metal from the values listed below. a. 918 °C (1684 °F)b. 900 °C (1652 °F)c. 882 °C (1620 °F)d. 400 °C (752 °F)

8. Radiometric imagers of what wavelength should be used for accurate surface temperature measurement of plate glass? a. wavelengths less than 1.0 μmb. wavelengths less than 4.5μm c. wavelengths greater than 4.5 µmd. wavelengths between 1.0 and 2.4μm


Glass Transmission Spectrum


9. Actual surfaces frequently exhibit variable emissivities over the wavelength spectrum. These surfaces are commonly referred to as: a. real bodiesb. graybodiesc. blackbodiesd. white bodies

10. The peak spectral radiance from a blackbody with a temperature of 1800 K (1526.85 °C) is: a. equal to that of a blackbody at 1800 °R (726.85 °C)b. twice that of a blackbody at 900 K (626.85 °C)c. less than that of a blackbody at 900 K (626.85 °C)d. greater than that of a blackbody at 900 K (626.85 °C)


11. What is the correct value of the Stefan-Boltzmann constant?a. 5.67 X 10-6 W/cmb. 5.67 x 10-12 W/m2

c. 5.67 x 10-8 W/m2∙K4

d. 5.67 x 10-8 W/cm2∙K4

12. Wien's displacement law for determining the peak wavelength of emitted radiation may be expressed as: (μm)a. λmax = 2897 /TK

b. λmax = TK∙2897C. λmax = 2.897/TK

d. λmax = 289.77/TK


13. A change in the electrical resistance of the responsive element in an infrared detector due to temperature changes produced by absorbed, incident infrared radiation describes the: a. thermovoltaic effectb. photovoltaic effectc. pyroelectric effectd. bolometric effect

14. The slit response method is the generally accepted method for determining IFOV measurement. What percent modulation is required to obtain an accurate temperature? a. greater than 90%b. less than 90%c. 50%d. none of the above


15. Thermographic stress analysis is based on which of the following effects that relates dynamic changes in stress to the temperature changes they produce:a. thermal conductivity effectb. thermal diffusivity effectc. thermoelastic effectd. thermal gradient effect


16 Vibrothermography is a nondestructive est method that involves monitoring the surface of a material with an infrared imager while the material is subjected to:a. forced mechanical oscillationsb. thermal wavesc. laser eXcitationd. sudden thermal shock

18. Thermal radiation is strongly absorbed by water vapor in which of the following wave bands?a. 3.5 to 5 μmb. 6 to 8 μmc. 9 to 10 μmd. 10 to 12 μm


18. The responsive element of infrared detectors can be divided into what two groups?a. reflective detectors and emissive detectorsb. thermal detectors and photon detectorsc. static detectors and dynamic detectorsd. quantitative detectors and qualitative detectors

19. A good material for making a lens for an infrared imager isa. germaniumb. graphite epoxyc. indium antimonided. glass


20. Heat is applied to the surface of a 0.635 cm (0.25 in.) graphite epoxy laminate. Which of the following statements are true?

a. when heat is applied evenly over the surface, heat flow will be multidirectional into the part

b. when heat is applied unevenly over the surface, heat flow will be one dimensional through the part

c. when heat is applied evenly over the surface, heat flow will be unidirectional through the part until a discontinuity is reached

d. when heat is applied evenly over the surface, heat flow will be multidirectional through the part until a discontinuity is reached


21. You are asked to determine the minimum defect size (surface indication) that can be resolved using a thermal imaging system with an IFOV of 1.5 milliradians. You are following ASTM 2582-07 which requires that nine contiguous 相邻的 pixels are projected within the boundaries of the indication. The minimum focus distance of the thermal imager is 60.96 cm (24 in.). Assuming the surface of the component has an emissivity of 0.94, what is the minimum defect size that can be resolved using the above system?a. 0.0914 cm (0.036 in.)b. 0.1829 cm (0.072 in.)c. 0.2743 cm (0.108 in.)d. 0.9144 cm (0.36 in.)


22. How do you know that an active pulse thermographic inspection of a material had sufficient power and inspection time?

a. using the log plot, look for a break in the straight line indicating heat hitting the back wall

b. using full power on the flash lamps will always provide sufficient power c. the peak contrast plot will indicate all possible indications are identified d. there is no way to determine sufficient power and time have been used

23. You are inspecting a 1 in. (2.54 cm) thick aluminum panel that has been heated to 50 ºC (122 ºF). A small surface hole in the panel appears warmer than the smooth surface surrounding it. Why?

a. the crack or hole has a higher emittance b. the surface emits less long wave thermal radiation c. the reflectivity of a crack or hole equals 0.9999 d. radiation-is not emitted by aluminum surfaces


24. What is the best surface preparation for using quartz lamps to conduct an active thermographic inspection of a composite component?

a. optically reflective and thermally reflective b. optically absorptive and thermally emissive c. optically absorptive and thermally neutral d. optically reflective and thermally emissive 25, For the purpose of thermally locating subsurface discontinuities; what is

the best method of applying heat to the surface of an 8 ply carbon fiber face sheet to detect a delamination between ply 1 and 2?

a. quartz lamps b. hot air gun c. incandescent heat lamp d. capacitor driven flash lamps


26. Thermal diffusivity is proportional to: a. emissivity times reflectivity b. heat capacitance c. thermal conductivity divided by heat capacitance d. spectral bandwidth divided by responsivity

27. You suspect that a potential defect indication in a sample may be due to a reflection from the flash lamp. What should you do to determine if the anomaly was a defect or a reflection?

a. unless the anomaly looks like a reflection of the lamp it must be a defect b. rotate the part and test again - if the anomaly moves with the part it is

probably a defect c. do destructive analysis to see if the indication was a defect d. flip the part over and inspect from the back side


Thermal DiffusivityIn heat transfer analysis, thermal diffusivity is the thermal conductivity divided by density and specific heat capacity at constant pressure.[1] It measures the ability of a material to conduct thermal energy relative to its ability to store thermal energy. It has the SI unit of m²/s. Thermal diffusivity is usually denoted α

α = k/(ρ∙Cp)

where:k is thermal conductivity (W/(m·K))ρ is density (kg/m³)Cp is specific heat capacity (J/(kg·K))

Together, ρCp, can be considered the volumetric heat capacity (J/(m3·K)).

https://en.wikipedia.org/wiki/Thermal_diffusivity


28. When using solvent to clean a test piece for thermal evaluation it is important to:

a. be sure the solvent is dry for 5 min before the inspect begins b. be sure the solvent has fully evaporated c. be sure the piece has returned to thermal equilibrium d. never use solvents before thermal NDT evaluations


29. According to.ASTM E2582-07, as the depth of a flaw increases, the size of the minimum detectable flaw must: a. remain the sameb. increasec. decreased. elongate

30. According to ASTM E2582-07, the optics and the focal plane should be sufficient so that the projection of nine contiguous pixels onto the sample plane is: a. greater than the minimum flaw areab. equal to or greater than the minimum flaw areac. less than the minimum flaw aread. less than or equal to the minimum flaw area


31. According to ASTM E2582-07, the peak contrast time of a subsurface defect depends on which of the following: a. depth of the flawb. orientation of the flawc. size of the flawd. depth and size of the flaw

32. For high-speed imaging (in excess of 60 frames per second), which of the following detector materials is most appropriate:a. PtSib. pyroelectric vidiconc. InSbd. mercury cadmium telluride


33. A pyroelectric vidicon is a _______ sensor.a. photonb. thermalc. bolometerd. thermal/pressure

34. The minimum resolvable temperature difference MRTD is a subjective measurement that depends on the: a. infrared imaging systems spatial resolution onlyb. infrared imaging systems thermal sensitivity and spatial resolutionc. infrared imaging systems measurement resolution onlyd. infrared imaging system's minimum spot size


35. The spatial resolution of an instrument isrelated to the:a. instantaneous field of view and the working distanceb. thermal resolution and the system detectivityc. spectral band width and the working distanced. system responsivity divided by the working distance

36. How does temperature affect the wavelength of infrared peak emittance of an object?a. lower temperature objects have shorter peak emittance wavelengthsb. higher temperature objects have shorter peak emittance wavelengthsc. temperature variations do not affect the wavelength of emitted radiationd. objects experiencing transient temperatures will emit longer waveswhen they are increasing in temperature and shorter waves when they are cooling


37. Of the following contact temperature sensors, which is considered to be the most accurate sensor?a. RTDsb. thermocouplesc. thermistorsd. liquid in glass thermometers


38. Which optical property changes due to temperature changes in liquid crystals?a. absorptivityb. reflectivityc. transmissivityd. emissivity

39. When heat is applied to an inspection surface for active nondestructive evaluation of a material, a thermogram will develop that is a function of the material, the nature of the discontinuity, the heat intensity and: a. the time of observationb, the wave band of the thermal imager usedc. the responsivity of the thermal detectord. surface roughness of the material


40. With respect to thermal nondestructive testing, an empirical rule of thumb says that the radius of the smallest detectable discontinuity should be at least ____ as its depth under the surface. a. one-quarter as largeb. one-half as largec. as larged. as large and preferably two or more times as large

41. What is the term used to describe a thermal NDT technique where mechanical vibrations are externally induced into a structure producing heat caused by frictiori at discontinuities such as cracks and delaminations?a. ultrasonic thermographyb. mechanically induced thermographyc. frictionally induced thermographyd. vibrothermography


42. The energy emitted by an object radiates from a surface layer that is how thick?a. 3 to 4 μmb. 10 μmc. 100 μmd. 200 to 400 μm

43. What are the two atmospheric gases that absorb transmitted radiation over the wave band of 1 to 15 μm?a. ozone and carbon dioxideb. oxygen and ozonec. water vapor and ozoned. water vapor and carbon dioxide


44. Minimum resolvable temperature difference is a subjective measurement that depends on the infrared imaging system's:a. thermal sensitivityb. spatial resolutionc. detectivity (D*)d. thermal sensitivity and spatial resolution

45. You are asked to choose a thermal irnaging camera for a critical inspection of an aerospace component. If an anomaly is present it is expected to have very subtle signal with an MRTD about 75 mK. Expected surface temperature is in the vicinity of 350 K. Which of the following detectors will provide the greatest thermal contrast?a. vanadium oxide microbolometer 8 to 12 μmb. mercury cadmium telluride 8 to 12μmc. lead selinide 3 to 5 μmd. indium antimonide 3.5 to 5 μm

Charlie Chong/ Fion Zhang http://newt.phys.unsw.edu.au/~jon/ir_eo.htm


46. When the radiant emission from a small opening in an isothermal enclosure is examined, the spectral response is found to closely approximate that of a:a. spectral bodyb. colored bodyc. blackbodyd. graybody

47. Which type of cryogenic cooling system for a photovoltaic type detector is perhaps the best choice for laboratory operation where reliability, quiet operation, and low temperature are required? a. joule-thompson gas expansion using argon gasb. sterling cooler using helium as coolantc. liquid nitrogen in a metal deward. thermoelectric coolers using the peltier effect


48. Which of following thermal detectors has the highest detectivity (D*)? a. InSbb. HgCdTec. pyro-electricd. micro bolometer

49. A material that has a flat spectral emissivity curve from 3 - 12μm isconsidered a:a. graybodyb. colored bodyc. blackbodyd. spectral body


50. An important and critical assumption when using two-color pyrometers is that a smooth curve exists between two variables. What are these two variables?a. roughness and calorb. emissivity and wavelengthc. emissivity and temperatured. spectral translucence and emissivity

51. Compared to a thermocouple, an advantage of a resistance temperature detector (RTD) is: a. less expensive than a thermocoupleb. more linear than a thermocouplec. wider temperature range than a thermocoupled. less stable than a thermocouple


52. One of the advantages of using thermocouples for temperature measurement over a resistance temperature detector (RTD) is:a. thermocouples are more ruggedb. thermocouples are more stablec. thermocouples are more accurated. thermocouples are more linear

53. One of the advantages of using a resistance temperature detector (RTD) over a thermocouple is RTDs:a. have a wide temperature rangeb. are self-poweredc. are more accurated. are more rugged


54. The seebeck effect is the basis for what temperature measurement device?a. liquid-in-glass thermometersb. thermocouplesc. thermistorsd. resistance temperature detectors


55. You are asked to choose a surface temperature measuring device that must meet the following criteria: wide tetnpefature range; operate in a variety of environments, simple to install, rugged and relatively inexpensive. Which of the followingdxevicesxmeets your requirenierits the best?a. liquid-in-glass thermometersb. resistance temperature detectorsc. thermistorsd. thermocouples

56. What material is used as the primary element in high-accuracy resistance thermometers?a. silverb. triglycene sulfatec. nickeld. platinumhttp://www.omega.com/temperature/Z/TheRTD.html


57. Distinguishing real temperature changes from apparent temperature changes is one of the biggest challenges facing infrared thermographers. Apparent temperature changes can be caused by differences in all of the following except:a. emissivityb. thermal diffusivityc. transmissivityd. target geometry

58. Which spectral range will you choose to measure the temperature of an object with a temperature range of 200 to 1000 °C (392 to 1532 °F), inside a heating chamber with a glass viewing port?a. 2 to 3 μmb. 4 to 5 μmc. 6 to 8 μmd. 8 to 13 μm


59, You are asked to measure the temperature of polyethelene at a temperattire tange 80 to 90°C (176 o194°F), What waveband and with which filter will you choose to make these temperature measurements?a. 3.4 to 5 μm with a 3.45 μm narrow band pass filter b. 3.4 to 5 μm with 4.8 μm high pass filter c. 8 to 13 μm with 7.9 μm lowpass filter d. 8 to 13 μm with a 10.3 μm narrow band pass filter

60. When capturing a series of thermal images that record a transient thermal event, such as occurs with pulse heating of a material to detect subsurface anomalies) most of the rapid changes in the thermal evolution curve occur in the time interval immediately following thermal excitation. It is beneficial to view the thermal images using what type of time scale?a. linearb. logarithmic ? (good guess)c. exponentiald. statistical


RTDThe same year that Seebeck made his discovery about thermoelectricity, Sir Humphrey Davy announced that the resistivity of metals showed a marked temperature dependence. Fifty years later, Sir William Siemens proffered the use of platinum as the element in a resistance thermometer. His choice proved most propitious, as platinum is used to this day as the primary element in all high-accuracy resistance thermometers.

Because of their lower resistivities, gold and silver are rarely used as RTD elements. Tungsten has a relatively high resistivity, but is reserved for very high temperature applications because it is extremely brittle and difficult to work.

http://www.omega.com/temperature/Z/TheRTD.html


End Of Reading


Good Luck