A Guide to Thermal Imaging Cameras

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Infrared Thermography Applications

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A guide to thermal imaging (Infrared or IR) 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 only getting a single number for temperature, you get a comprehensive visual image or 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.

Are there any limitations to thermal imaging (IR) cameras?

Yes!  Thermal energy can be reflected off of shiny surfaces such as polished metal and glass.  Thermal imaging cameras cannot see through glass which is an immediate indicator of a low tech device claiming to offer ‘infrared imaging’ to the end user.  Some tablets and smart phones today tout IR technology yet are actually presenting a visual image that has been digitally manipulated to look like a thermogram.  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, infrared cameras cannot 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 what and if a problem exists.

Digital image storage and infrared cameras

Digital image storage, available on FLIR and most other upper level infrared cameras, produces calibrated thermal images that contain between 20,000 and 300,000 independent temperature measurements.  These measurements can then be analyzed with simple yet powerful reporting software to provide precise information and professional reports in both digital or hard copy formats.  And with a specific time and date stamp affixed to every thermogram image captured, you can use the information to create baseline and trending reports which may indicate wear, developing issues and call for attention to equipment  far in advance of actual failure.  This is one of infrared’s most powerful impacts.

How do I get a good image from my Infrared camera?

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.