The 4 sates of matter are what? Name the fourth.
1. Solid
2. Liquids
3. gases
D) plasmas
Matter can form other matter.
False
Matter can only combine with other matter to form compounds
The basic structural components of the universe are?
B) matter
Energy and matter are associated with each other.
True
the first law of thermodynamics is the law of ______________?
A) conservation of energy
Absolute zero is what temperature?
0 kelvin or -273 centigrade
The reason the efficiency of any process will always be less than 100% is?
As disorder increases in the universe (entropy) energy transforms into less usable forms.
The first of law of thermodynamics states what?
This is what allows us to determine the efficiency of a system
The total amount of energy in the universe is constant.
If all movement of matter stops at -273C or 0 kelvin then this means what cannot occur at this temperature?
C) The transfer of energy cannot occur.
mind blown
The two types of energy are what?
kinein to move GREEK kinētikos
Kinetic and Potential
Chemical energy is found where
This is stored in the bonds of atoms and molecules
This is a form of energy that travels in transverse waves
The oscillation of the electrical field of the wave moves perpendicular to the direction the wave is travelling, making it a transverse wave.
electromagnetic energy
This is formed when and electric field couples with a magnetic field.
Electromagnetic waves
This is also called the end light spectrum. This includes gamma rays, x-rays, ultraviolet, visible light, infrared, microwave, and radio wave.
Courtesy Bureau Veritas
electromagnetic spectrum.
This has longer cycles compared to ultraviolet and visible light. It has a lower frequency.
Recall that when they discovered the universe was expanding they realized this because they saw colors of red in the light. Thus the wavelengths are very long
Infrared light or radiation.
Light absorption, reflection, and emission spectra is a physical property of an object?
False
The human eye responds to wavelengths of light at what length?
380-750 nanometers
The frequency of light is a trillion times faster than the frequency at your electrical outlet.
True
430THz Tara hertz
The term used to measure the number of cycles per a unit of time is what?
named after Heinrich Rudolf Hertz (1857–1894), the first person to provide conclusive proof of the existence of electromagnetic waves.
frequency. Expressed in Hertz
When radiant energy is absorbed by an object, that object simultaneously emits the same amount of energy that was absorbed.
True
This is similar to the ground heating up in the sunlight.
absorbs and emits
D) In general, the higher the temperature, and the more opaque and reflective, the more infrared radiation it _________.
Consider carbon used in Graphene that absorbs all light and is 300 times stronger than steel. It is considered a superb conductor.
Disorder in the universe causes energy to change into more usable forms
False
less usable forms. Consider that order; for example a bridge, is actually chaos to the natural world. Thus steel bridging is a less usable form of energy.
The basis of all thermal testing is based on what 4 criteria represented by the acronym TEAR
4. Transmission
1. Emission
2. Absorption
3. Reflection
Is low wavelength thermal energy able to pass through glass or most other materials?
Germanium is used for the lenses on infrared thermal cameras.
TRUE
The effects of transmissivity for most materials is insignificant when compared to reflectivity, but still must be factored when determining a material's absorptive and emissive properties.
blackbody radiation is the energy emitted by materials that absorb energy similar to a black body.
True
blackbody radiation, energy radiated by any object or system that absorbs all incident radiation. The term usually refers to the spectrum of light emitted by any heated object; common examples include the heating element of a toaster and the filament of a light bulb.
Infrared passes through glass.
consider a green house and why it gets hotter
False
The glass heats up and then radiates heat to its surroundings that allows them to radiate.
To ensure that there is a full pixel on the target there must be ___ array of pixels for temperature reading.
D) 3x3
Which of the following are elements we must understand to create a good thermal image?
D) dynamic range and all of the rest
individual temperatures in an infrared image are displayed as colors and shades of a?
D) palette
Emissivity is considered a ratio. What is the ratio of a black body?
The lower the emissivity the harder it is to predict the exact temperature of an object.
A black body has an emissivity of 0%. The emissivity is the percent of total energy radiated at a given surface at a temperature given/to the total energy radiated by a blackbody at the same temperature.
A thermal surface with an emissivity of 0 would have no thermal emittance and appears black.
A perfect thermal mirror has an emissivity of 0.
False
radiated/ blackbody radiated means 0 is 0 energy radiated thus all energy is reflected and a black body at 1 would be a perfect emitter
What during thermal scanning in commissioning can provide a perfect reflection and lead to a false temperature reading?
Anything shiny. Specifically anthing with an emissivity of 0 since it is a Perfect Thermal Mirror.
Two concepts used to understand the relationship between an objects infrared radiation level and its surface temperature.
C) Planck's Blackbody Distribution Law & Wien's Law of Displacement
The radiation of a perfectly emitting blackbody intensifies as it's temperature does. Wiens law illustrates that infrared is a longer wavelength than what you can see with the naked eye but you may see it if it becomes intense enough.
Wien's Displacement Law is stated how? Select the BEST answer.
If the materials emissivity is known, Wien's Law allows us to use wavelengths, or frequencies, to determine the surface temperature.
A) That the temeprature of an object increases, the peak INTENSITY moves to shorter wavelengths.
The light in the visible spectrum is shorter and as infrared radiation intensifies it becomes shorter in wavelenth.
The purpose of Wien's Law?
As the temperature of an object increases, the peak intensity moves to shorter wavelengths
What law allows us to calculate the surface temperature in infrared?
Planck's Blackbody Distribution Law states that the intensity of radiation emitted from an object is a function of it's temperature, wavelength, and emissivity.
True
Shiny surfaces have high emissivity and high reflectivity
False
The emissivity of a shiny surface is low. Think of emit as the root word. It reflects highly. Thus it cannot absorb and emit infrared radiation well.
Infrared cameras display the temperature based on?
B) emissivity
infrared sensor temperature x emissivity = actual temperature
the relative power of a surface to emit heat by radiation
the more reflective the surface, the lower the absorptivity and emissivity of the material.
D) emissivity
a measure of the ability of a surface to radiate energy; the ratio of the radiant flux emitted per unit area to that emitted by a black body at the same temperature
tape emissivity x metal temperature ÷ tape temperature is used to find a metal's emissivity
True
You can accurately measure emissivity for objects at the same temperature as the background.
False
If the object and background temperature are equal, the camera will see the same result no matter the emissivity.
When a reflective object is emitting energy to the IR camera, it emits according to its emissivity and its temperature.
False
An opaque object is emitting energy to the IR camera, it emits according to its emissivity and its temperature. Reflective objects have a low emissivity because emissivity is a ratio. a measure of the ability of a surface to radiate energy; the ratio of the radiant flux emitted per unit area to that emitted by a black body at the same temperature
For opaque objects, reflectivity is complementary to emissivity and is equal to one, minus the objects emissivity.
True
when it reflects energy to the IR camera, it does so according to its reflectivity and
D) the temperature in the background.
the temperature in the background is necessarily in variation or nothing would be identified or seen.
The emissivity of black electrical tape is what?
B) .97
emissivity is a ratio of the radiation reflected / that reflected by a black body. at the same temperature.
Tape emissivityx metal temperature ÷ tape temperature= metal emissivity
True
Keep in mind that this method is less accurate if the metal is too close to room temperature. As metal tends to reflect the ambient temperature around it.
Using the determining material types equation (Tape emissivity x metal temperature ÷ tape temperature = metal emissivity) what must you keep in mind that would make the method less accurate?
If the metal is too close to room temperature, as metal tends to reflect the ambient temperature around it.
Perfect black bodies are materials that emit energy and have an emissivity of?
D) 1
emissivity is a ratio of the radiation emitted/ black body radiation at the same temperature. A black body is an idealized object that absorbs all electromagnetic radiation it comes in contact with. It then emits thermal radiation in a continuous spectrum according to its temperature.
A black body emits all electromagnetic energy?
False
A black body is an idealized object that absorbs all electromagnetic radiation it comes in contact with. It then emits thermal radiation in a continuous spectrum according to its temperature.
A black body absorbs thermal radiation in a continuous spectrum according to its temperature.
False
A black body is an idealized object that absorbs all electromagnetic radiation it comes in contact with. It then emits thermal radiation in a continuous spectrum according to its temperature.
When performing an IR scan, the target is assumed to be a grey body rather than a black body. Why?
Grey bodies have an emissivity less than one that is constant through wavelengths. Black bodies emit all thermal energy (but absorbs all electromagnetic energy)
If an IR camera measures an object with a temperature of Absolute Zero, the reading would come back Absolute Zero, regardless of what?
B) of what the emissivity of that object is
The temperature is absolute zero which means no exchange of energy can occur.
The degree to which infrared energy is absorbed by a material.
A) absorption
all materials are continuously and simultaneously conducting and absorbing infrared energy is a true statement. The best answer is however given.
If absorption is the degree of infrared energy absorbed by a material and absorptivity is the proportion of radiant energy that is absorbed into the material, then what would a real world material reflect if it is a black body that perfectly absorbs. Considering thermal radiation.
A real world black body cannot be a perfect black body as it will always reflect a small part of the incident radiation, resulting in absorptivity that is always less than one.
What is the difference between absorption and absorptivity?
absorptivity is the opposite phenomenon to emissivity which is the proportion of infrared energy radiating from a surface, and infrared energy is instead absorbed by the material
If absorption is the degree to which infrared energy is absorbed & absorptivity is the proportion of radiant energy that is absorbed.
Remember: the more reflective the surface, the lower the absorptivityand emissivity of the material.
reflectivity is what?
D) ratio of the intensity of the total energy reflected from the surface to the radiation on that surface.
The degree to which infrared energy reflects off a material is reflection and not reflectivity.
To accurately calculate the emissivity of an object what must be added?
the ratio of the amount of electromagnetic flux reflected by a surface to the total amount of electromagnetic flux incident on the surface is defined by this term.
D) ratio of reflectivity must be added to the total in order to accurately calculate this.
The ratio of reflectivity is the ratio of the amount of electromagnetic flux reflected by a surface to the total amount of electromagnetic flux incident on the surface.
The degree to which thermal energy passes through a material.
A) transmission
Kirchoff's law states that?
D) the ratio of radiation intensities for two surfaces is equal to the ratio of their absorptivity
Gustav Robert Kirchoff came up with many laws.
Good reflectors are good emitters.
False
Kirchoff's radiation law explains why good reflectors are always bad emitters, and vice versa.
convection versus conduction. What is the difference?
The movement of particles through a substance, transporting their heat energy from hotter areas to cooler areas is convection. Conduction however, doesn't necessarily involve particles moving. Instead energy is passed from one particle to another upon contact from a solid surface, transferring heat.
This is the fastest method of heat transfer., heat is transferred by electromagnetic waves traveling at the speed of light.
D) radiation
The total energy of an object is expressed using one of two formulas with only one difference between them. What is it? Regarding Kirchhoff's law regarding the ratio of radiation.
transmissivity is (physics) a measure of the capacity of a material to transmit radiation
absorptivity & emissivity are the only difference in total energy of an object with both regarding transmissivity
absorptivity + reflectivity + transmissivity = total energy
emissivity + reflectivity + transmissivity = total energy
range is the temperature difference than an infrared camera can measure?
True
What does the first and second law of thermodynamics state?
in the thermography test it will ask if the total amount of energy in the universe is constant. Answer true even though this is in violation of the law as this would not be a closed system
1. First Law of Thermodynamics states that total energy in a closed system is neither lost nor gained — it is only transformed.
2.The Second Law of Thermodynamics states that entropy constantly increases in a closed system.
What is the difference between transient heat flow and steady state flow?
In transient heat transfers, the heat energy transferred through the medium is not constant. The heat flow rate keeps changing, and the cause of the varying rates of heat transfer can be either fluctuating temperature differences over the medium or changes in properties of the medium.
Steady-state conduction occurs when the temperature at all locations in a substance is constant with time. Thermal conductivity is an important property of matter. It accounts for the heat conducting ability of a substance and depends both on the particular substance involved and on the state of that substance
The transfer of heat through a moving medium such as a liquid or gas.
A) convection
passive devices emit signals and radiation and ignore what the target emits?
False
Passive thermography does not require any active illumination (such as lights) or specialized equipment, making it extremely useful for inspections in dark or enclosed spaces. Active thermography is the use of emitters to illuminate objects with infrared light and then take images using an infrared camera.
What causes the temperature of a given point to change over time?
B) transient heat flow
During a change of the state of matter, the supplied energy is not used to increase the kinetic energy of the molecules, but to change the binding energies. Therefore, the temperature remains constant.
Heat transfer comprises convection & conduction but not radiation as this is energy and not heat.
True
radiation is a form of energy transfer as all exchanges of temperature difference are forms of energy.
The basis of quantitative analysis is always comparing dissimilar equipment under similar loads?
pay close attention to the words being used.
False
qualitative (not quantitative) similar equipment under similar loads.
A direct reading measures the surface temperature of the target without other insulating materials affecting the results.
motors, steam traps, and tank levels are all forms of indirect readings
True
This is always the easiest way to perform a quantitative analysis. indirect uses insulation and is very difficult.
This form of analysis is done using a baseline inspection performed with subsequent inspections to build a thermal map to determine if any changes have occurred over time.
C) qualitative evaluation
this is a comparison.
As the temperature increases the thermal resistance decreases?
False
As the temperature decreases, thermal resistance increases. Think conductivity.
The larger the surface, the greater the loss of thermal resistance as the temperature decreases.
True
The loss of thermal resistance is more because the area is larger and resistance always decreases as directly proportional to temperature and thus area as well.
It is sometimes necessary to heat a cold room in order to locate this with thermal imaging.
C) trapped moisture
It makes sense because cold air would transition slower than the air around it to the new temperature.
Thermal Anomalies can be grouped into which categories?
there are 5 forms of thermal anomalies: think not as seen.
The difference between endothermic and exothermic reactions is endothermic reactions draw heat in from their surroundings and exothermic reactions give heat off to their surroundings.
True
For field quantification it is required that proper device calibration requires that the thermographer factors the emissivity of the object into the calibration.
True
a lower emissivity setting is used for highly reflected objects and a high emissivity setting is used for low reflective objects. Where emissivity is the amount of radiation emitted by an object compared to the amount emitted by a perfect emitter at the same temperature.
During FIELD QUANTIFICATION where a baseline temperature is used for determining operating temperature limits, correctly adjusting the emissivity settings is unimportant when taking measurements because correct settings will appear hotter or colder than what they really are due to baseline measurements.
False
adjusting the emissivity settings is important when taking measurements because INCORRECT settings will appear hotter or colder than what they really are
We can determine emissivity through the following procedure.
1. apply a known emissivity coating to the unknown object.
2. heat the object and emissivity coating to 60F above the background temp.
3. set the camera emissivity to .95, target the black vinyl tape. record its temp.
4. target a part of the heated object next to the tape and lower the camera's emissivity setting until the temperature displayed matches the temperature previously recorded for the tape.
The key to a successful measurement is to have a measurement location where the background temperature is significantly less that the object temperature.
Shiny objects have high emissivity?
False
Emissivity is defined as the ratio of the energy radiated from a material's surface to that radiated from a perfect emitter, known as a blackbody, at the same temperature and wavelength and under the same viewing conditions. It is a dimensionless number between 0 (for a perfect reflector) and 1 (for a perfect emitter). Thus shiny would be the opposite of a black body at 1 and give incorrect readings for temperature as high.
IF A THERMAL imager set for a high emissivity is used to measure an object with lose emissivity, the following occurs. :
In an object that has low emissivity and is shiny, the measured object is warmer than ambient temperature, the reading will be much higher than the object's actual temperature.
high emissivity with a low emissivity object will skew the results.
False
IF THE MEASURED OBJECT IS WARMER THAN AMBIENT: the reading will be much LOWER than the object's actual temperature.
IF A THERMAL imager set for a high emissivity is used to measure an object with lose emissivity, the following occurs:
In an object that has low emissivity and is shiny, the measured object is COLDER than ambient temperature, the reading will be much HIGHER than the object's actual temperature.
high emissivity with a low emissivity object will skew the results.
True
IF A THERMAL imager set for a high emissivity is used to measure an object with lose emissivity, the following occurs. IF THE MEASURED OBJECT IS COLDER THAN AMBIENT: the reading will be much HIGHER than the object's actual temperature.
Polished metals like stainless steel have a very high emissivity. This occurs because the metal is primarily reflecting the thermal radiation from its surroundings.
in emissivity a perfect reflector is 0 and a blackbody is 1. Because ratio of the energy radiated from a material's surface to that radiated from a perfect emitter, known as a blackbody that always would be 1 if perfect.
False
polished or shiny means a low emissivity because it would be 0 for a perfect reflector.
If we heat stainless steel to 150F and look at it with the infrared camera set for the same emissivity of .95, the camera will report a surface temperature how?
A) much lower than the objects temperature. because the surrounding emissivity.
adjusting the emissivity value on the thermal imager until the reading matches 150 will provide an emissivity of .12 Remember a perfect reflector is 0.
Thermal anomalies are visible to the human eye?
False
We call them anomalies because what we see is our primary sense and thus nomalous or normal.
Most thermal imaging inspections for predictive maintenance use a quantitative approach.
False
Most thermal imaging inspections for predictive maintenance use a qualitative approach that is more concerned with differences between similar components under similar loads than with precise, quantitative temperature measurement.
What is the difference between quantitative and qaulitative?
Quantitative data is numbers-based, countable, or measurable. Qualitative data is interpretation-based, descriptive, and relating to language
Most thermal imaging inspections for predictive maintenance use a quantitative approach.
True
Most thermal imaging inspections for predictive maintenance use a qualitative approach that is more concerned with differences between similar components under similar loads than with precise, quantitative temperature measurement.
The infrared camera has a lens made of what?
This is made of germanium and is usually several thousand dollars in cost.
What are the three forms of energy the infrared camera can see?
emissivity
transmitted
reflective
Does reflective stainless have a low or high emissivity?
This type of material would have a very low emissivity.
What is an example of an artifact?
In thermography, an emissivity artifact simulates a change in surface temperature but is not a real change. A hot solar reflection or a cold reflection due to narcissus would be examples of artifacts.
Copper to copper bus bar is allowed what difference in temperature?
30 degrees F is allowed for this deviation.
When writing a thermography report and using the F or C notation there is a difference between the change in temperature and the reference. What is this?
The use of °F means a difference whereas F° means the reference.
What should you do with the camera prior to taking reliable temperature data?
The camera should be on for 15 minutes so that heat can sync into the components.
Atmoshperic temperature and room temperature need to be updated and changed when?
Whenever you go inside or outside. Also high heat and humidity say 90F with 85% humidity the signal of infrared is attenuated (absorbed in the atmosphere).
What must you do when looking through the IR windows?
The compensation must be set to 50. EXT. OPTICS TRANS. in the camera menu. If set to 1.00 it does not assume it is looking through the IR window. Typically made of calcium fluoride.
Can an infrared camera see through glass?
No. The IR camera can not look through this type of material.
Author
johnbowens
ID
359761
Card Set
Thermal Scanning & Thermistivity in Comissioning
Description
The use of a thermal scanner in finding heat bodies in commissioning
