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Thermal Imaging Cameras

Temperature is very important in our everyday lives and is used for many applications such as to see if you are sick, if food is cooked thoroughly or if your car is overheating. Thermal imaging cameras take measuring temperature to the next level where instead of getting a number for the temperature, you get a picture showing the temperature differences of a surface. Thermal imaging, also known as thermography, is the technique for producing an image of invisible (to our eyes) infrared light emitted by objects with the use of a thermal imaging camera. Thermal imaging cameras provide rapid scanning of a surface that is non-destructive and environmentally friendly, which allows for quick detection of potential problems or defects that will reduce troubleshooting time and preventative maintenance.

What do thermal imaging cameras see?
Thermal imaging cameras don’t actually see temperature. Instead they capture the infrared (IR) energy transfer from an object to its environment and produce a real time image in a color palette where hotter objects appear brighter and cooler objects appear darker. IR energy is generated by the vibration of atoms and molecules and behaves similarly to visible light where it can be reflected, refracted, absorbed and emitted. The more these atoms and molecules move, the higher the temperature of the object.

What applications can a thermal imaging camera be used?
Thermal imaging cameras are becoming a common tool in the home inspection industry where they are being used to verify building performance to specifications, to determine the insulation is installed or in good condition, locate air leaks, verify structure design and locate moisture intrusion. Of course these are not the only applications to which it can be used. Their use is limited to the imagination of the user. Primarily it is used where the identification of thermal patterns can be used to find something or diagnose a condition such as poor insulation in a home or an overloaded electrical circuit. Some examples include:

• Substation electrical inspections
• Thermal heat loss inspections of buildings
• Locate radiant heating wires or pipes
• Locate potential areas for mold growth
• Flat roof leak detection for buildings
• Detect thermal patterns on boiler tubes
• Mechanical bearing inspections
• Detect insulation leaks in refrigeration equipment

What are some of the features of thermal imaging cameras?
Basically, a thermal imaging camera is capable of, saving the thermal image to either its internal memory or to a memory card depending on the camera capabilities. Once the user has completed taking the images, they can be viewed and edited on the camera or downloaded to a PC where the images can be formatted on a report with the software that is included. Thermal imaging cameras can be purchased with the bare minimum of features that will only read the temperature of the fixed center crosshairs on the display, where other cameras will allow the user to select multiply moveable crosshairs and compare the temperatures between them or the box area feature that will show the high, low and average temperature within a box on the display. Thermal imaging cameras will have multiple color palettes such as black/white, iron or rainbow that are user selectable. The iron palette is most commonly used by home inspectors, the black/white palette helps identify details on an image and the rainbow palette has the best thermal sensitivity for displaying the differences in temperature. See sample images below of some color palettes.

	Iron palette of fuse bus bar
	Black/White/Gray palette
	Rainbow palette
	Hot metal palette
	Amber palette

More sophisticated cameras may include:

	A color alarm feature that allows the user to select a temperature and the camera will only display a color thermal image of anything that is either above or below the selected temperature.
	A picture-in-picture feature that will display a color thermal image (which is a quarter of the size of the display) inside a standard digital image. Temperature readings are limited to only the thermal portion of this feature.
	An IR Fusion feature that allows the user to blend either the maximum, minimum or average temperature of the thermal image with a standard digital image.

How do I get a good image?
Using a thermal imaging camera is quite simple, but interpreting the image captured takes knowledge and experience. To help a user obtain the best thermal image to analyze, there are four adjustments that can be made to the camera; focusing, changing the emissivity setting, changing the reflective temperature setting and thermal tuning.

• Just like a standard camera, the lens of the thermal imaging camera will need to be focused to enhance the clarity of the image. Most cameras can be focused by twisting the lens where more sophisticated cameras will have a push button focus.

• Emissivity is the amount of radiation emitted from an object compared to that of a perfect emitter of radiation when both are at the same temperature. A lower emissivity setting would be used for highly reflected objects and a high emissivity setting would be used for low reflective objects. Objects that are non-metal or that have a rougher surface will have a higher emissivity. Adjusting the emissivity is important when taking temperature measurements or when comparing two different objects temperatures. Incorrect emissivity settings will make objects appear hotter or colder then what they really are. Not all cameras will allow the user to adjust the emissivity of the camera and will be defaulted to wood or drywall.

• The reflective temperature setting allows the user to compensate for surrounding objects temperature reflecting on an object. If reflecting thermal energy from surrounding objects is suspected, move the camera around in the area of the target and see if the hot or cold spot moves with the camera. If it does, it is a reflection from another object, if it does not, it is a true hot or cold spot. In order to find out what the reflective temperature is, the user will need to adjust the emissivity of the camera to 1.0, then place a piece of crinkled aluminum foil on a piece of cardboard. Hold the foil between the camera and the object you intend to view and note the temperature of the foil. Then input the temperature of the foil in the reflective temperature setting on the camera. Just like emissivity, reflective temperature is important when taking temperature measurements or comparing two objects temperatures. Not all cameras will allow the user to input reflective temperature.

• Thermal tuning the camera involves adjusting the span or temperature range that the camera sees while in manual viewing mode. Thermal imaging cameras will have an automatic viewing mode and manual viewing mode. When the camera is in automatic mode, the camera will automatically adjust the temperature scale to what is being viewed which causes the display to change colors frequently when the camera is moved. Manual mode allows the user to adjust the span to a desired range and the camera will always display this temperature range. Using the manual mode is best used to bring out temperature differences of the object being viewed.

Are there any limitations to thermal imaging cameras?
Because thermal energy can be reflected off of shiny surfaces, thermal imaging cameras can not see through glass. If you stand in front of a window while looking at a thermal imaging camera, you will see yourself in the window because of the thermal energy reflecting off the glass. Regardless of what Hollywood movies may show, thermal imaging cameras can not see through walls. It is also important to know that thermal imaging cameras should not be used as the deciding factor that a problem exists. Using other instruments such as a borescope, moisture meter, multimeter or blueprint drawing of the building should always be used to confirm the problem.

To purchase a thermal imaging camera, please click here for different camera options.

Sources for More Information

For more information please visit:

http://www.infraredtraining.com

http://infraredtraining.com/ir_primer.asp

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Please Note: The information contained in this publication is intended for general information purposes only. This publication is not a substitute for review of the applicable government regulations and standards, and should not be construed as legal advice or opinion. Readers with specific questions should refer to the cited regulation or consult with an attorney.